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documentation.suse.com / Administration Guide
SUSE Linux Enterprise Server 15 SP5

Administration Guide

This guide covers system administration tasks like maintaining, monitoring and customizing an initially installed system.

Publication Date: June 20, 2024
List of Figures
List of Examples

Copyright © 2006–2024 SUSE LLC and contributors. All rights reserved.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or (at your option) version 1.3; with the Invariant Section being this copyright notice and license. A copy of the license version 1.2 is included in the section entitled GNU Free Documentation License.

For SUSE trademarks, see https://www.suse.com/company/legal/. All third-party trademarks are the property of their respective owners. Trademark symbols (®, ™ etc.) denote trademarks of SUSE and its affiliates. Asterisks (*) denote third-party trademarks.

All information found in this book has been compiled with utmost attention to detail. However, this does not guarantee complete accuracy. Neither SUSE LLC, its affiliates, the authors nor the translators shall be held liable for possible errors or the consequences thereof.

Preface

1 Available documentation

Online documentation

Our documentation is available online at https://documentation.suse.com. Browse or download the documentation in various formats.

Note
Note: Latest updates

The latest updates are usually available in the English-language version of this documentation.

SUSE Knowledgebase

If you have run into an issue, also check out the Technical Information Documents (TIDs) that are available online at https://www.suse.com/support/kb/. Search the SUSE Knowledgebase for known solutions driven by customer need.

Release notes

For release notes, see https://www.suse.com/releasenotes/.

In your system

For offline use, the release notes are also available under /usr/share/doc/release-notes on your system. The documentation for individual packages is available at /usr/share/doc/packages.

Many commands are also described in their manual pages. To view them, run man, followed by a specific command name. If the man command is not installed on your system, install it with sudo zypper install man.

2 Improving the documentation

Your feedback and contributions to this documentation are welcome. The following channels for giving feedback are available:

Service requests and support

For services and support options available for your product, see https://www.suse.com/support/.

To open a service request, you need a SUSE subscription registered at SUSE Customer Center. Go to https://scc.suse.com/support/requests, log in, and click Create New.

Bug reports

Report issues with the documentation at https://bugzilla.suse.com/.

To simplify this process, click the Report an issue icon next to a headline in the HTML version of this document. This preselects the right product and category in Bugzilla and adds a link to the current section. You can start typing your bug report right away.

A Bugzilla account is required.

Contributions

To contribute to this documentation, click the Edit source document icon next to a headline in the HTML version of this document. This will take you to the source code on GitHub, where you can open a pull request.

A GitHub account is required.

Note
Note: Edit source document only available for English

The Edit source document icons are only available for the English version of each document. For all other languages, use the Report an issue icons instead.

For more information about the documentation environment used for this documentation, see the repository's README.

Mail

You can also report errors and send feedback concerning the documentation to <>. Include the document title, the product version, and the publication date of the document. Additionally, include the relevant section number and title (or provide the URL) and provide a concise description of the problem.

3 Documentation conventions

The following notices and typographic conventions are used in this document:

  • /etc/passwd: Directory names and file names

  • PLACEHOLDER: Replace PLACEHOLDER with the actual value

  • PATH: An environment variable

  • ls, --help: Commands, options, and parameters

  • user: The name of a user or group

  • package_name: The name of a software package

  • Alt, AltF1: A key to press or a key combination. Keys are shown in uppercase as on a keyboard.

  • File, File › Save As: menu items, buttons

  • AMD/Intel This paragraph is only relevant for the AMD64/Intel 64 architectures. The arrows mark the beginning and the end of the text block.

    IBM Z, POWER This paragraph is only relevant for the architectures IBM Z and POWER. The arrows mark the beginning and the end of the text block.

  • Chapter 1, Example chapter: A cross-reference to another chapter in this guide.

  • Commands that must be run with root privileges. You can also prefix these commands with the sudo command to run them as a non-privileged user:

    # command
    > sudo command
  • Commands that can be run by non-privileged users:

    > command
  • Commands can be split into two or multiple lines by a backslash character (\) at the end of a line. The backslash informs the shell that the command invocation will continue after the line's end:

    > echo a b \
    c d
  • A code block that shows both the command (preceded by a prompt) and the respective output returned by the shell:

    > command
    output
  • Notices

    Warning
    Warning: Warning notice

    Vital information you must be aware of before proceeding. Warns you about security issues, potential loss of data, damage to hardware, or physical hazards.

    Important
    Important: Important notice

    Important information you should be aware of before proceeding.

    Note
    Note: Note notice

    Additional information, for example about differences in software versions.

    Tip
    Tip: Tip notice

    Helpful information, like a guideline or a piece of practical advice.

  • Compact Notices

    Note

    Additional information, for example about differences in software versions.

    Tip

    Helpful information, like a guideline or a piece of practical advice.

4 Support

Find the support statement for SUSE Linux Enterprise Server and general information about technology previews below. For details about the product lifecycle, see https://www.suse.com/lifecycle.

If you are entitled to support, find details on how to collect information for a support ticket at https://documentation.suse.com/sles-15/html/SLES-all/cha-adm-support.html.

4.1 Support statement for SUSE Linux Enterprise Server

To receive support, you need an appropriate subscription with SUSE. To view the specific support offers available to you, go to https://www.suse.com/support/ and select your product.

The support levels are defined as follows:

L1

Problem determination, which means technical support designed to provide compatibility information, usage support, ongoing maintenance, information gathering and basic troubleshooting using available documentation.

L2

Problem isolation, which means technical support designed to analyze data, reproduce customer problems, isolate a problem area and provide a resolution for problems not resolved by Level 1 or prepare for Level 3.

L3

Problem resolution, which means technical support designed to resolve problems by engaging engineering to resolve product defects which have been identified by Level 2 Support.

For contracted customers and partners, SUSE Linux Enterprise Server is delivered with L3 support for all packages, except for the following:

  • Technology previews.

  • Sound, graphics, fonts, and artwork.

  • Packages that require an additional customer contract.

  • Some packages shipped as part of the module Workstation Extension are L2-supported only.

  • Packages with names ending in -devel (containing header files and similar developer resources) will only be supported together with their main packages.

SUSE will only support the usage of original packages. That is, packages that are unchanged and not recompiled.

4.2 Technology previews

Technology previews are packages, stacks, or features delivered by SUSE to provide glimpses into upcoming innovations. Technology previews are included for your convenience to give you a chance to test new technologies within your environment. We would appreciate your feedback. If you test a technology preview, please contact your SUSE representative and let them know about your experience and use cases. Your input is helpful for future development.

Technology previews have the following limitations:

  • Technology previews are still in development. Therefore, they may be functionally incomplete, unstable, or otherwise not suitable for production use.

  • Technology previews are not supported.

  • Technology previews may only be available for specific hardware architectures.

  • Details and functionality of technology previews are subject to change. As a result, upgrading to subsequent releases of a technology preview may be impossible and require a fresh installation.

  • SUSE may discover that a preview does not meet customer or market needs, or does not comply with enterprise standards. Technology previews can be removed from a product at any time. SUSE does not commit to providing a supported version of such technologies in the future.

For an overview of technology previews shipped with your product, see the release notes at https://www.suse.com/releasenotes.

Part I Common tasks

  • 1 Bash and Bash scripts
  • Today, many people use computers with a graphical user interface (GUI) like GNOME. Although GUIs offer many features, they are limited when performing automated task execution. Shells complement GUIs well, and this chapter gives an overview of several aspects of shells, in this case the Bash shell.

  • 2 sudo basics
  • Running certain commands requires root privileges. However, for security reasons and to avoid mistakes, it is not recommended to log in as root. A safer approach is to log in as a regular user, and then use sudo to run commands with elevated privileges.

  • 3 Using YaST
  • YaST is a SUSE Linux Enterprise Server tool that provides a graphical interface for all essential installation and system configuration tasks. Whether you need to update packages, configure a printer, modify firewall settings, set up an FTP server, or partition a hard disk—you can do it using YaST. …

  • 4 YaST in text mode
  • The ncurses-based pseudo-graphical YaST interface is designed primarily to help system administrators to manage systems without an X server. The interface offers several advantages compared to the conventional GUI. You can navigate the ncurses interface using the keyboard, and there are keyboard sho…

  • 5 Changing language and country settings with YaST
  • This chapter explains how to configure language and country settings. You can change the language globally for the whole system, individually for certain users or desktops, or temporarily for single applications. Additionally, you can configure secondary languages and adjust the date and country settings.

  • 6 Managing users with YaST
  • During installation, you may have created a local user for your system. With the YaST module User and Group Management you can add users or edit existing ones. It also lets you configure your system to authenticate users with a network server.

  • 7 YaST online update
  • SUSE offers a continuous stream of software security updates for your product. By default, the update applet is used to keep your system up to date. Refer to Section 8.5, “The GNOME package updater” for further information on the update applet. This chapter covers the alternative tool for updating s…

  • 8 Installing or removing software
  • Using YaST's software management module, you can search for software packages as well as install and remove them. When installing packages, YaST automatically resolves all dependencies. To install packages that are not on the installation medium, you can add software repositories and YaST to manage them. You can also keep your system up to date by managing software updates using the update applet.

  • 9 Managing software with command line tools
  • This chapter describes Zypper and RPM, two command line tools for managing software. For a definition of the terminology used in this context (for example, repository, patch, or update) refer to Section 8.1, “Definition of terms”.

  • 10 System recovery and snapshot management with Snapper
  • Snapper allows creating and managing file system snapshots. File system snapshots allow keeping a copy of the state of a file system at a certain point of time. The standard setup of Snapper is designed to allow rolling back system changes. However, you can also use it to create on-disk backups of user data. As the basis for this functionality, Snapper uses the Btrfs file system or thinly-provisioned LVM volumes with an XFS or Ext4 file system.

  • 11 Live kernel patching with KLP
  • This document describes the basic principles of the Kernel Live Patching (KLP) technology, and provides usage guidelines for the SLE Live Patching service.

  • 12 User space live patching
  • This chapter describes the basic principles and usage of user space live patching.

  • 13 Transactional updates
  • Transactional updates are available in SUSE Linux Enterprise Server as a technology preview, for updating SLES when the root file system is read-only. Transactional updates are atomic (all updates are applied only if all updates succeed) and support rollbacks. It does not affect a running system as no changes are activated until after the system is rebooted. As reboots are disruptive, the administrator must decide if a reboot is more expensive than disturbing running services. If reboots are too expensive then do not use transactional updates.

    Transactional updates are run daily by the transactional-update script. The script checks for available updates. If there are any updates, it creates a new snapshot of the root file system in the background, and then fetches updates from the release channels. After the new snapshot is completely updated, it is marked as active and will be the new default root file system after the next reboot of the system. When transactional-update is set to run automatically (which is the default behavior) it also reboots the system. Both the time that the update runs and the reboot maintenance window are configurable.

    Only packages that are part of the snapshot of the root file system can be updated. If packages contain files that are not part of the snapshot, the update could fail or break the system.

    RPMs that require a license to be accepted cannot be updated.

  • 14 Remote graphical sessions with VNC
  • Virtual Network Computing (VNC) enables you to access a remote computer via a graphical desktop, and run remote graphical applications. VNC is platform-independent and accesses the remote machine from any operating system. This chapter describes how to connect to a VNC server with the desktop clients vncviewer and Remmina, and how to operate a VNC server.

    SUSE Linux Enterprise Server supports two different kinds of VNC sessions: one-time sessions that live While the VNC connection from the client is kept up, and persistent sessions that live until they are explicitly terminated.

    A VNC server can offer both kinds of sessions simultaneously on different ports, but an open session cannot be converted from one type to the other.

  • 15 File copying with RSync
  • Today, a typical user has several computers: home and workplace machines, a laptop, a smartphone or a tablet. This makes the task of keeping files and documents in synchronization across multiple devices all the more important.

1 Bash and Bash scripts

Today, many people use computers with a graphical user interface (GUI) like GNOME. Although GUIs offer many features, they are limited when performing automated task execution. Shells complement GUIs well, and this chapter gives an overview of several aspects of shells, in this case the Bash shell.

1.1 What is the shell?

Traditionally, the Linux shell is Bash (Bourne again Shell). When this chapter speaks about the shell it means Bash. There are more shells available (ash, csh, ksh, zsh, …), each employing different features and characteristics. If you need further information about other shells, search for shell in YaST.

1.1.1 Bash configuration files

A shell can be invoked as an:

  1. Interactive login shell.  This is used when logging in to a machine, invoking Bash with the --login option or when logging in to a remote machine with SSH.

  2. Ordinary interactive shell.  This is normally the case when starting xterm, konsole, gnome-terminal, or similar command line interface (CLI) tools.

  3. Non-interactive shell.  This is invoked when invoking a shell script at the command line.

Each shell reads different configuration files. The following tables show the login and non-login shell configuration files.

Tip
Tip

Bash looks for its configuration files in a specific order depending on the type of shell where it is run. Find more details on the Bash man page (man 1 bash). Search for the headline INVOCATION.

Table 1.1: Bash configuration files for login shells

File

Description

/etc/profile

Do not modify this file, otherwise your modifications may be destroyed during your next update!

/etc/profile.local

Use this file if you extend /etc/profile

/etc/profile.d/

Contains system-wide configuration files for specific programs

~/.profile

Insert user specific configuration for login shells here

The login shell also sources the configuration files listed under Table 1.2, “Bash configuration files for non-login shells”.

Table 1.2: Bash configuration files for non-login shells

/etc/bash.bashrc

Do not modify this file, otherwise your modifications may be destroyed during your next update.

/etc/bash.bashrc.local

Use this file to insert your system-wide modifications for Bash only

~/.bashrc

Insert user specific configuration here

Additionally, Bash uses multiple files:

Table 1.3: Special files for Bash

File

Description

~/.bash_history

Contains a list of all commands you have typed

~/.bash_logout

Executed when logging out

~/.alias

User defined aliases of frequently used commands. See man 1 alias for more details about defining aliases.

No-Login Shells

There are special shells that block users from logging into the system: /bin/false and /sbin/nologin. Both fail silently when the user attempts to log into the system. This was intended as a security measure for system users, though modern Linux operating systems have more effective tools for controlling system access, such as PAM and AppArmor.

The default on SUSE Linux Enterprise Server is to assign /bin/bash to human users, and /bin/false or /sbin/nologin to system users. The nobody user has /bin/bash for historical reasons, as it is a user with minimum privileges that used to be the default for system users. However, whatever little bit of security gained by using nobody is lost when multiple system users use it. It should be possible to change it to /sbin/nologin; the fastest way to test it is change it and see if it breaks any services or applications.

Use the following command to list which shells are assigned to all users, system and human users, in /etc/passwd. The output varies according to the services and users on your system:

> sort -t: -k 7 /etc/passwd | awk -F: '{print $1"\t" $7}' | column -t
tux               /bin/bash
nobody            /bin/bash
root              /bin/bash
avahi             /bin/false
chrony            /bin/false
dhcpd             /bin/false
dnsmasq           /bin/false
ftpsecure         /bin/false
lightdm           /bin/false
mysql             /bin/false
postfix           /bin/false
rtkit             /bin/false
sshd              /bin/false
tftp              /bin/false
unbound           /bin/false
bin               /sbin/nologin
daemon            /sbin/nologin
ftp               /sbin/nologin
lp                /sbin/nologin
mail              /sbin/nologin
man               /sbin/nologin
nscd              /sbin/nologin
polkitd           /sbin/nologin
pulse             /sbin/nologin
qemu              /sbin/nologin
radvd             /sbin/nologin
rpc               /sbin/nologin
statd             /sbin/nologin
svn               /sbin/nologin
systemd-coredump  /sbin/nologin
systemd-network   /sbin/nologin
systemd-timesync  /sbin/nologin
usbmux            /sbin/nologin
vnc               /sbin/nologin
wwwrun            /sbin/nologin
messagebus        /usr/bin/false
scard             /usr/sbin/nologin

1.1.2 The directory structure

The following table provides a short overview of the most important higher-level directories that you find on a Linux system. Find more detailed information about the directories and important subdirectories in the following list.

Table 1.4: Overview of a standard directory tree

Directory

Contents

/

Root directory—the starting point of the directory tree.

/bin

Essential binary files, such as commands that are needed by both the system administrator and normal users. Usually also contains the shells, such as Bash.

/boot

Static files of the boot loader.

/dev

Files needed to access host-specific devices.

/etc

Host-specific system configuration files.

/home

Holds the home directories of all users who have accounts on the system. However, root's home directory is not located in /home but in /root.

/lib

Essential shared libraries and kernel modules.

/media

Mount points for removable media.

/mnt

Mount point for temporarily mounting a file system.

/opt

Add-on application software packages.

/root

Home directory for the superuser root.

/sbin

Essential system binaries.

/srv

Data for services provided by the system.

/tmp

Temporary files.

/usr

Secondary hierarchy with read-only data.

/var

Variable data such as log files.

/windows

Only available if you have both Microsoft Windows* and Linux installed on your system. Contains the Windows data.

The following list provides more detailed information and gives some examples of which files and subdirectories can be found in the directories:

/bin

Contains the basic shell commands that may be used both by root and by other users. These commands include ls, mkdir, cp, mv, rm and rmdir. /bin also contains Bash, the default shell in SUSE Linux Enterprise Server.

/boot

Contains data required for booting, such as the boot loader, the kernel, and other data that is used before the kernel begins executing user-mode programs.

/dev

Holds device files that represent hardware components.

/etc

Contains local configuration files that control the operation of programs like the X Window System. The /etc/init.d subdirectory contains LSB init scripts that can be executed during the boot process.

/home/USERNAME

Holds the private data of every user who has an account on the system. The files located here can only be modified by their owner or by the system administrator. By default, your e-mail directory and personal desktop configuration are located here in the form of hidden files and directories, such as .gconf/ and .config.

Note
Note: Home directory in a network environment

If you are working in a network environment, your home directory may be mapped to a directory in the file system other than /home.

/lib

Contains the essential shared libraries needed to boot the system and to run the commands in the root file system. The Windows equivalent for shared libraries are DLL files.

/media

Contains mount points for removable media, such as CD-ROMs, flash disks, and digital cameras (if they use USB). /media generally holds any type of drive except the hard disk of your system. When your removable medium has been inserted or connected to the system and has been mounted, you can access it from here.

/mnt

This directory provides a mount point for a temporarily mounted file system. root may mount file systems here.

/opt

Reserved for the installation of third-party software. Optional software and larger add-on program packages can be found here.

/root

Home directory for the root user. The personal data of root is located here.

/run

A tmpfs directory used by systemd and various components. /var/run is a symbolic link to /run.

/sbin

As the s indicates, this directory holds utilities for the superuser. /sbin contains the binaries essential for booting, restoring and recovering the system in addition to the binaries in /bin.

/srv

Holds data for services provided by the system, such as FTP and HTTP.

/tmp

This directory is used by programs that require temporary storage of files.

Important
Important: Cleaning up /tmp at boot time

Data stored in /tmp is not guaranteed to survive a system reboot. It depends, for example, on settings made in /etc/tmpfiles.d/tmp.conf.

/usr

/usr has nothing to do with users, but is the acronym for Unix system resources. The data in /usr is static, read-only data that can be shared among various hosts compliant with the Filesystem Hierarchy Standard (FHS). This directory contains all application programs including the graphical desktops such as GNOME and establishes a secondary hierarchy in the file system. /usr holds several subdirectories, such as /usr/bin, /usr/sbin, /usr/local, and /usr/share/doc.

/usr/bin

Contains generally accessible programs.

/usr/sbin

Contains programs reserved for the system administrator, such as repair functions.

/usr/local

In this directory the system administrator can install local, distribution-independent extensions.

/usr/share/doc

Holds various documentation files and the release notes for your system. In the manual subdirectory find an online version of this manual. If more than one language is installed, this directory may contain versions of the manuals for different languages.

Under packages find the documentation included in the software packages installed on your system. For every package, a subdirectory /usr/share/doc/packages/PACKAGENAME is created that often holds README files for the package and sometimes examples, configuration files or additional scripts.

If HOWTOs are installed on your system /usr/share/doc also holds the howto subdirectory in which to find additional documentation on many tasks related to the setup and operation of Linux software.

/var

Whereas /usr holds static, read-only data, /var is for data which is written during system operation and thus is variable data, such as log files or spooling data. For an overview of the most important log files you can find under /var/log/, refer to Table 48.1, “Log files”.

1.2 Writing shell scripts

Shell scripts provide a convenient way to perform a wide range of tasks: collecting data, searching for a word or phrase in a text and other useful things. The following example shows a small shell script that prints a text:

Example 1.1: A shell script printing a text
#!/bin/sh 1
# Output the following line: 2
echo "Hello World" 3

1

The first line begins with the Shebang characters (#!) which indicate that this file is a script. The interpreter, specified after the Shebang, executes the script. In this case, the specified interpreter is /bin/sh.

2

The second line is a comment beginning with the hash sign. We recommend that you comment difficult lines. With proper commenting, you can remember the purpose and function of the line. Also, other readers can better understand your script. Commenting is considered good practice in the development community.

3

The third line uses the built-in command echo to print the corresponding text.

Before you can run this script, there are a few prerequisites:

  1. Every script should contain a Shebang line (as in the example above). If the line is missing, you need to call the interpreter manually.

  2. You can save the script wherever you want. However, it is a good idea to save it in a directory where the shell can find it. The search path in a shell is determined by the environment variable PATH. A normal user does not have write access to /usr/bin. Therefore it is recommended to save your scripts in the users' directory ~/bin/. The above example gets the name hello.sh.

  3. The script needs executable permissions. Set the permissions with the following command:

    > chmod +x ~/bin/hello.sh

If you have fulfilled all the above prerequisites, you can execute the script in the following ways:

  1. As absolute path.  The script can be executed with an absolute path. In our case, it is ~/bin/hello.sh.

  2. Everywhere.  If the PATH environment variable contains the directory where the script is located, you can execute the script with hello.sh.

1.3 Redirecting command events

Each command can use three channels, either for input or output:

  • Standard output.  This is the default output channel. Whenever a command prints something, it uses the standard output channel.

  • Standard input.  If a command needs input from users or other commands, it uses this channel.

  • Standard error.  Commands use this channel for error reporting.

To redirect these channels, there are the following possibilities:

Command > File

Saves the output of the command into a file, the existing file is deleted. For example, the ls command writes its output into the file listing.txt:

> ls > listing.txt
Command >> File

Appends the output of the command to a file. For example, the ls command appends its output to the file listing.txt:

> ls >> listing.txt
Command < File

Reads the file as input for the given command. For example, the read command reads in the content of the file into the variable:

> read a < foo
Command1 | Command2

Redirects the output of the left command as input for the right command. For example, the cat command outputs the content of the /proc/cpuinfo file. This output is used by grep to filter only those lines which contain cpu:

> cat /proc/cpuinfo | grep cpu

Every channel has a file descriptor: 0 (zero) for standard input, 1 for standard output and 2 for standard error. It is allowed to insert this file descriptor before a < or > character. For example, the following line searches for a file starting with foo, but suppresses its errors by redirecting it to /dev/null:

> find / -name "foo*" 2>/dev/null

1.4 Using aliases

An alias is a shortcut definition of one or more commands. The syntax for an alias is:

alias NAME=DEFINITION

For example, the following line defines an alias lt that outputs a long listing (option -l), sorts it by modification time (-t), and prints it in reverse sorted order (-r):

> alias lt='ls -ltr'

To view all alias definitions, use alias. Remove your alias with unalias and the corresponding alias name.

1.5 Using variables in Bash

A shell variable can be global or local. Global variables, or environment variables, can be accessed in all shells. In contrast, local variables are visible in the current shell only.

To view all environment variables, use the printenv command. If you need to know the value of a variable, insert the name of your variable as an argument:

> printenv PATH

A variable, be it global or local, can also be viewed with echo:

> echo $PATH

To set a local variable, use a variable name followed by the equal sign, followed by the value:

> PROJECT="SLED"

Do not insert spaces around the equal sign, otherwise you get an error. To set an environment variable, use export:

> export NAME="tux"

To remove a variable, use unset:

> unset NAME

The following table contains common environment variables that you can use in you shell scripts:

Table 1.5: Useful environment variables

HOME

the home directory of the current user

HOST

the current host name

LANG

when a tool is localized, it uses the language from this environment variable. English can also be set to C

PATH

the search path of the shell, a list of directories separated by colon

PS1

specifies the normal prompt printed before each command

PS2

specifies the secondary prompt printed when you execute a multi-line command

PWD

current working directory

USER

the current user

1.5.1 Using argument variables

For example, if you have the script foo.sh you can execute it like this:

> foo.sh "Tux Penguin" 2000

To access all the arguments which are passed to your script, you need positional parameters. These are $1 for the first argument, $2 for the second, and so on. You can have up to nine parameters. To get the script name, use $0.

The following script foo.sh prints all arguments from 1 to 4:

#!/bin/sh
echo \"$1\" \"$2\" \"$3\" \"$4\"

If you execute this script with the above arguments, you get:

"Tux Penguin" "2000" "" ""

1.5.2 Using variable substitution

Variable substitutions apply a pattern to the content of a variable either from the left or right side. The following list contains the possible syntax forms:

${VAR#pattern}

removes the shortest possible match from the left:

> file=/home/tux/book/book.tar.bz2
> echo ${file#*/}
home/tux/book/book.tar.bz2
${VAR##pattern}

removes the longest possible match from the left:

> file=/home/tux/book/book.tar.bz2
> echo ${file##*/}
book.tar.bz2
${VAR%pattern}

removes the shortest possible match from the right:

> file=/home/tux/book/book.tar.bz2
> echo ${file%.*}
/home/tux/book/book.tar
${VAR%%pattern}

removes the longest possible match from the right:

> file=/home/tux/book/book.tar.bz2
> echo ${file%%.*}
/home/tux/book/book
${VAR/pattern_1/pattern_2}

substitutes the content of VAR from the PATTERN_1 with PATTERN_2:

> file=/home/tux/book/book.tar.bz2
> echo ${file/tux/wilber}
/home/wilber/book/book.tar.bz2

1.6 Grouping and combining commands

Shells allow you to concatenate and group commands for conditional execution. Each command returns an exit code which determines the success or failure of its operation. If it is 0 (zero) the command was successful, everything else marks an error which is specific to the command.

The following list shows, how commands can be grouped:

Command1 ; Command2

executes the commands in sequential order. The exit code is not checked. The following line displays the content of the file with cat and then prints its file properties with ls regardless of their exit codes:

> cat filelist.txt ; ls -l filelist.txt
Command1 && Command2

runs the right command, if the left command was successful (logical AND). The following line displays the content of the file and prints its file properties only, when the previous command was successful (compare it with the previous entry in this list):

> cat filelist.txt && ls -l filelist.txt
Command1 || Command2

runs the right command, when the left command has failed (logical OR). The following line creates only a directory in /home/wilber/bar when the creation of the directory in /home/tux/foo has failed:

> mkdir /home/tux/foo || mkdir /home/wilber/bar
funcname(){ ... }

creates a shell function. You can use the positional parameters to access its arguments. The following line defines the function hello to print a short message:

> hello() { echo "Hello $1"; }

You can call this function like this:

> hello Tux

which prints:

Hello Tux

1.7 Working with common flow constructs

To control the flow of your script, a shell has while, if, for and case constructs.

1.7.1 The if control command

The if command is used to check expressions. For example, the following code tests whether the current user is Tux:

if test $USER = "tux"; then
  echo "Hello Tux."
else
  echo "You are not Tux."
fi

The test expression can be as complex or simple as possible. The following expression checks if the file foo.txt exists:

if test -e /tmp/foo.txt ; then
  echo "Found foo.txt"
fi

The test expression can also be abbreviated in square brackets:

if [ -e /tmp/foo.txt ] ; then
  echo "Found foo.txt"
fi

Find more useful expressions at https://bash.cyberciti.biz/guide/If..else..fi.

1.7.2 Creating loops with the for command

The for loop allows you to execute commands to a list of entries. For example, the following code prints certain information about PNG files in the current directory:

for i in *.png; do
 ls -l $i
done

1.8 More information

Important information about Bash is provided in the man pages man bash. More about this topic can be found in the following list:

2 sudo basics

Running certain commands requires root privileges. However, for security reasons and to avoid mistakes, it is not recommended to log in as root. A safer approach is to log in as a regular user, and then use sudo to run commands with elevated privileges.

On SUSE Linux Enterprise Server, sudo is configured to work similarly to su. However, sudo provides a flexible mechanism that allows users to run commands with privileges of any other user. This can be used to assign roles with specific privileges to certain users and groups. For example, it is possible to allow members of the group users to run a command with the privileges of user wilber. Access to the command can be further restricted by disallowing any command options. While su always requires the root password for authentication with PAM, sudo can be configured to authenticate with your own credentials. This means that the users do not need to share the root password, which improves security.

2.1 Basic sudo usage

The following chapter provides an introduction to basic usage of sudo.

2.1.1 Running a single command

As a regular user, you can run any command as root by adding sudo before it. This prompts you to provide the root password. If authenticated successfully, this runs the command as root:

> id -un1
tux
> sudo id -un
root's password:2
root
> id -un
tux3
> sudo id -un
4
root

1

The id -un command prints the login name of the current user.

2

The password is not shown during input, neither as clear text nor as masking characters.

3

Only commands that start with sudo run with elevated privileges.

4

The elevated privileges persist for a certain period of time, so you do not need to provide the root password again.

Tip
Tip: I/O redirection

When using sudo, I/O redirection does not work:

> sudo echo s > /proc/sysrq-trigger
bash: /proc/sysrq-trigger: Permission denied
> sudo cat < /proc/1/maps
bash: /proc/1/maps: Permission denied

In the example above, only the echo and cat commands run with elevated privileges. The redirection is done by the user's shell with user privileges. To perform redirection with elevated privileges, either start a shell as in Section 2.1.2, “Starting a shell” or use the dd utility:

echo s | sudo dd of=/proc/sysrq-trigger
sudo dd if=/proc/1/maps | cat

2.1.2 Starting a shell

Using sudo every time to run a command with elevated privileges is not always practical. While you can use the sudo bash command, it is recommended to use one of the built-in mechanisms to start a shell:

sudo -s (<command>)

Starts a shell specified by the SHELL environment variable or the target user's default shell. If a command is specified, it is passed to the shell (with the -c option). Otherwise the shell runs in interactive mode.

tux:~ > sudo -s
root's password:
root:/home/tux # exit
tux:~ > 
sudo -i (<command>)

Similar to -s, but starts the shell as a login shell. This means that the shell's start-up files (.profile etc.) are processed, and the current working directory is set to the target user's home directory.

tux:~ > sudo -i
root's password:
root:~ # exit
tux:~ > 
Tip
Tip: Environment variables

By default, sudo does not propagate environment variables. This behavior can be changed using the env_reset option (see Useful flags and options).

2.2 Configuring sudo

sudo provides a wide range on configurable options.

Note
Note: Locked yourself out of sudo

If you accidentally locked yourself out of sudo, use su - and the root password to start a root shell. To fix the error, run visudo.

2.2.1 Editing the configuration files

The main policy configuration file for sudo is /etc/sudoers. As it is possible to lock yourself out of the system if the file is malformed, it is strongly recommended to use visudo for editing. It prevents editing conflicts and checks for syntax errors before saving the modifications.

You can use another editor instead of vi by setting the EDITOR environment variable, for example:

sudo EDITOR=/usr/bin/nano visudo

Keep in mind that the /etc/sudoers file is supplied by the system packages, and modifications done directly in the file may break updates. Therefore, it is recommended to put custom configuration into files in the /etc/sudoers.d/ directory. Use the following command to create or edit a file:

sudo visudo -f /etc/sudoers.d/NAME

The command bellow opens the file using a different editor (in this case, nano):

sudo EDITOR=/usr/bin/nano visudo -f /etc/sudoers.d/NAME
Note
Note: Ignored files in /etc/sudoers.d

The #includedir directive in /etc/sudoers ignores files that end with the ~ (tilde) character or contain the . (dot) character.

For more information on the visudo command, run man 8 visudo.

2.2.2 Basic sudoers configuration syntax

The sudoers configuration files contain two types of options: strings and flags. While strings can contain any value, flags can be turned either ON or OFF. The most important syntax constructs for sudoers configuration files are as follows:

# Everything on a line after # is ignored 1
Defaults !insults # Disable the insults flag 2
Defaults env_keep += "DISPLAY HOME" # Add DISPLAY and HOME to env_keep
tux ALL = NOPASSWD: /usr/bin/frobnicate, PASSWD: /usr/bin/journalctl 3

1

There are two exceptions: #include and #includedir are regular commands.

2

Remove the ! character to set the desired flag to ON.

3

See Section 2.2.3, “Basic sudoers rules”.

Useful flags and options
targetpw

This flag controls whether the invoking user is required to enter the password of the target user (ON) (for example root) or the invoking user (OFF).

Defaults targetpw # Turn targetpw flag ON
rootpw

If set, sudo prompts for the root password. The default is OFF.

Defaults !rootpw # Turn rootpw flag OFF
env_reset

If set, sudo constructs a minimal environment with TERM, PATH, HOME, MAIL, SHELL, LOGNAME, USER, USERNAME, and SUDO_*. Additionally, variables listed in env_keep are imported from the calling environment. The default is ON.

Defaults env_reset # Turn env_reset flag ON
env_keep

List of environment variables to keep when the env_reset flag is ON.

# Set env_keep to contain EDITOR and PROMPT
Defaults env_keep = "EDITOR PROMPT"
Defaults env_keep += "JRE_HOME" # Add JRE_HOME
Defaults env_keep -= "JRE_HOME" # Remove JRE_HOME
env_delete

List of environment variables to remove when the env_reset flag is OFF.

# Set env_delete to contain EDITOR and PROMPT
Defaults env_delete = "EDITOR PROMPT"
Defaults env_delete += "JRE_HOME" # Add JRE_HOME
Defaults env_delete -= "JRE_HOME" # Remove JRE_HOME

The Defaults token can also be used to create aliases for a collection of users, hosts, and commands. Furthermore, it is possible to apply an option only to a specific set of users.

For detailed information about the /etc/sudoers configuration file, consult man 5 sudoers.

2.2.3 Basic sudoers rules

Each rule follows the following scheme ([] marks optional parts):

#Who      Where         As whom      Tag                What
User_List Host_List = [(User_List)] [NOPASSWD:|PASSWD:] Cmnd_List
sudoers rule syntax
User_List

One or several (separated by comma) identifiers: either a user name, a group in the format %GROUPNAME, or a user ID in the format #UID. Negation can be specified with the ! prefix.

Host_List

One or several (separated by comma) identifiers: either a (fully qualified) host name or an IP address. Negation can be specified with the ! prefix. ALL is a common choice for Host_List.

NOPASSWD:|PASSWD:

The user is not prompted for a password when running commands matching Cmd_List after NOPASSWD:.

PASSWD is the default. It only needs to be specified when both PASSWD and NOPASSWD are on the same line:

tux ALL = PASSWD: /usr/bin/foo, NOPASSWD: /usr/bin/bar
Cmnd_List

One or several (separated by comma) specifiers: a path to an executable, followed by an optional allowed argument.

/usr/bin/foo     # Anything allowed
/usr/bin/foo bar # Only "/usr/bin/foo bar" allowed
/usr/bin/foo ""  # No arguments allowed

ALL can be used as User_List, Host_List, and Cmnd_List.

A rule that allows tux to run all commands as root without entering a password:

tux ALL = NOPASSWD: ALL

A rule that allows tux to run systemctl restart apache2:

tux ALL = /usr/bin/systemctl restart apache2

A rule that allows tux to run wall as admin with no arguments:

tux ALL = (admin) /usr/bin/wall ""
Warning
Warning: Unsafe rules

Do not use rules like ALL ALL = ALL without Defaults targetpw. Otherwise anyone can run commands as root.

Important
Important: Winbind and sudo

When specifying the group name in the sudoers file, make sure that you use the NetBIOS domain name instead of the realm, for example:

%DOMAIN\\GROUP_NAME ALL = (ALL) ALL

Keep in mind that when using winbindd, the format also depends on the winbind separator option in the smb.conf file. By default, it is \. If it is changed, for example, to +, then the account format in the sudoers file must be DOMAIN+GROUP_NAME.

2.3 sudo use cases

While the default configuration works for standard usage scenarios, you can customize the default configuration to meet your specific needs.

2.3.1 Using sudo without root password

By design, members of the group wheel can run all commands with sudo as root. The following procedure explains how to add a user account to the wheel group.

  1. Verify that the wheel group exists:

    > getent group wheel

    If the previous command returned no result, install the system-group-wheel package that creates the wheel group:

    > sudo zypper install system-group-wheel
  2. Add your user account to the group wheel.

    If your user account is not already a member of the wheel group, add it using the sudo usermod -a -G wheel USERNAME command. Log out and log in again to enable the change. Verify that the change was successful by running the groups USERNAME command.

  3. Authenticate with the user account's normal password.

    Create the file /etc/sudoers.d/userpw using the visudo command (see Section 2.2.1, “Editing the configuration files”) and add the following:

    Defaults !targetpw
  4. Select a new default rule.

    Depending on whether you want users to re-enter their passwords, uncomment the appropriate line in /etc/sudoers and comment out the default rule.

    ## Uncomment to allow members of group wheel to execute any command
    # %wheel ALL=(ALL) ALL
    
    ## Same thing without a password
    # %wheel ALL=(ALL) NOPASSWD: ALL
  5. Make the default rule more restrictive.

    Comment out or remove the allow-everything rule in /etc/sudoers:

    ALL     ALL=(ALL) ALL   # WARNING! Only use this together with 'Defaults targetpw'!
    Warning
    Warning: Dangerous rule in sudoers

    Do not skip this step. Otherwise any user can execute any command as root!

  6. Test the configuration.

    Run sudo as member and non-member of wheel.

    tux:~ > groups
    users wheel
    tux:~ > sudo id -un
    tux's password:
    root
    wilber:~ > groups
    users
    wilber:~ > sudo id -un
    wilber is not in the sudoers file.  This incident will be reported.

2.3.2 Using sudo with X.Org applications

Starting graphical applications with sudo normally results in the following error:

> sudo xterm
xterm: Xt error: Can't open display: %s
xterm: DISPLAY is not set

A simple workaround is to use xhost to temporarily allow the root user to access the local user's X session. This is done using the following command:

xhost si:localuser:root

The command below removes the granted access:

xhost -si:localuser:root
Warning
Warning: Potential security issue

Running graphical applications with root privileges has security implications. It is recommended to enable root access for a graphical application only as an exception. It is also recommended to revoke the granted root access as soon as the graphical application is closed.

2.4 More information

The sudo --help command offers a brief overview of the available command line options, while the man sudoers command provides detailed information about sudoers and its configuration.

3 Using YaST

YaST is a SUSE Linux Enterprise Server tool that provides a graphical interface for all essential installation and system configuration tasks. Whether you need to update packages, configure a printer, modify firewall settings, set up an FTP server, or partition a hard disk—you can do it using YaST. Written in Ruby, YaST features an extensible architecture that makes it possible to add new functionality via modules.

Additional information about YaST is available on the project's official Web site at https://yast.opensuse.org/.

3.1 YaST interface overview

YaST has two graphical interfaces: one for use with graphical desktop environments like KDE and GNOME, and an ncurses-based pseudo-graphical interface for use on systems without an X server (see Chapter 4, YaST in text mode).

In the graphical version of YaST, all modules in YaST are grouped by category, and the navigation sidebar allows you to quickly access modules in the desired category. The search field at the top makes it possible to find modules by their names. To find a specific module, enter its name into the search field, and you should see the modules that match the entered string as you type.

Important
Important: List of installed YaST modules

The list of installed modules for the ncurses-based and GUI version of YaST may differ. Before starting any YaST module, verify that it is installed for the version of YaST that you are using.

3.2 Useful key combinations

The graphical version of YaST supports keyboard shortcuts

Print Screen

Take and save a screenshot. It may not work on certain desktop environments.

ShiftF4

Enable and disable the color palette optimized for visually impaired users.

ShiftF7

Enable/disable logging of debug messages.

ShiftF8

Open a file dialog to save log files to a user-defined location.

CtrlShiftAltD

Send a DebugEvent. YaST modules can react to this by executing special debugging actions. The result depends on the specific YaST module.

CtrlShiftAltM

Start and stop macro recorder.

CtrlShiftAltP

Replay macro.

CtrlShiftAltS

Show stylesheet editor.

CtrlShiftAltT

Dump widget tree to the log file.

CtrlShiftAltX

Open a terminal window (xterm). Useful for installation process via VNC.

CtrlShiftAltY

Show widget tree browser.

4 YaST in text mode

The ncurses-based pseudo-graphical YaST interface is designed primarily to help system administrators to manage systems without an X server. The interface offers several advantages compared to the conventional GUI. You can navigate the ncurses interface using the keyboard, and there are keyboard shortcuts for practically all interface elements. The ncurses interface is light on resources, and runs fast even on modest hardware. You can run the ncurses-based version of YaST via an SSH connection, so you can administer remote systems. Keep in mind that the minimum supported size of the terminal emulator in which to run YaST is 80x25 characters.

Main window of YaST in text mode
Figure 4.1: Main window of YaST in text mode

To launch the ncurses-based version of YaST, open the terminal and run the sudo yast2 command. Use the →| or arrow keys to navigate between interface elements like menu items, fields and buttons. All menu items and buttons in YaST can be accessed using the appropriate function keys or keyboard shortcuts. For example, you can cancel the current operation by pressing F9, while the F10 key can be used to accept the changes. Each menu item and button in YaST's ncurses-based interface has a highlighted letter in its label. This letter is part of the keyboard shortcut assigned to the interface element. For example, the letter Q is highlighted in the Quit button. This means that you can activate the button by pressing AltAlt+Q.

Tip
Tip: Refreshing YaST dialogs

If a YaST dialog gets corrupted or distorted (for example, while resizing the window), press CtrlL to refresh and restore its contents.

4.1 Navigation in modules

The following description of the control elements in the YaST modules assumes that all function keys and Alt key combinations work and are not assigned to different global functions. Read Section 4.3, “Restriction of key combinations” for information about possible exceptions.

Moving between buttons and selection lists

Use →| to move between the buttons and frames containing selection lists. To navigate in the opposite direction, use Alt→| or Shift→| combinations.

Navigating in selection lists

Use the arrow keys ( and ) to move through the individual elements in an active frame containing a selection list. If individual entries are longer than the frame's width, use Shift or Shift to scroll horizontally. If the arrow key causes the selection to move to another frame, use CtrlE or CtrlA instead.

Working with buttons, radio buttons, and check boxes

To select items with empty square brackets (check boxes) or empty parentheses (radio buttons), press Space or Enter. Alternatively, radio buttons and check boxes can be selected directly with Althighlighted_letter. In this case, you do not need to confirm with Enter. If you navigate to an item with →|, press Enter to execute the selected action or activate the respective menu item.

Function keys

The function keys (from F1 to F12) enable quick access to the specific buttons. Available function key combinations (FX) are shown in the bottom line of the YaST screen. Which function keys are really mapped to which buttons depend on the active YaST module, because the different modules offer different buttons (Details, Info, Add, Delete, etc.). Use F10 for Accept, OK, Next, and Finish. Press F1 to access the YaST help.

Using the navigation tree

Some YaST modules use a navigation tree in the left part of the window to select configuration dialogs. Use the arrow keys ( and ) to navigate in the tree. Use Space to open or close tree items. In the ncurses mode, Enter must be pressed after a selection in the navigation tree to show the selected dialog. This is an intentional behavior to save time-consuming redraws when browsing through the navigation tree.

Selecting software in the software installation module

Use the filters on the left side to list packages matching the specified string. Installed packages are marked with the letter i. To change the status of a package, press Space or Enter. Alternatively, use the Actions menu to select the needed status change (install, delete, update, taboo or lock).

The software installation module
Figure 4.2: The software installation module

4.2 Advanced key combinations

The ncurses-based version of YaST offers several advanced key combinations.

ShiftF1

List advanced hotkeys.

ShiftF4

Change color schema.

CtrlQ

Quit the application.

CtrlL

Refresh screen.

CtrlDF1

List advanced hotkeys.

CtrlDShiftD

Dump dialog to the log file as a screenshot.

CtrlDShiftY

Open YDialogSpy to see the widget hierarchy.

4.3 Restriction of key combinations

If your window manager uses global Alt combinations, the Alt combinations in YaST may not work. Keys like Alt or Shift can also be occupied by the settings of the terminal.

Using Alt instead of Esc

Alt shortcuts can be executed with Esc instead of Alt. For example, EscH replaces AltH. (Press Esc, then press H.)

Backward and forward navigation with CtrlF and CtrlB

If the Alt and Shift combinations are taken over by the window manager or the terminal, use the combinations CtrlF (forward) and CtrlB (backward) instead.

Restriction of function keys

The function keys (F1 ... F12) are also used for functions. Certain function keys may be taken over by the terminal and may not be available for YaST. However, the Alt key combinations and function keys should always be fully available on a text-only console.

4.4 YaST command line options

Besides the text mode interface, YaST provides a command line interface. To get a list of YaST command line options, use the following command:

> sudo yast -h

4.4.1 Installing packages from the command line

If you know the package name, and the package is provided by an active installation repository, you can use the command line option -i to install the package:

> sudo yast -i package_name

or

> sudo yast --install -i package_name

package_name can be a single short package name (for example gvim) installed with dependency checking, or the full path to an RPM package, which is installed without dependency checking.

While YaST offers basic functionality for managing software from the command line, consider using Zypper for more advanced package management tasks. Find more information on using Zypper in Section 9.1, “Using Zypper”.

4.4.2 Working with individual modules

To save time, you can start individual YaST modules using the following command:

> sudo yast module_name

View a list of all modules available on your system with yast -l or yast --list.

4.4.3 Command line parameters of YaST modules

To use YaST functionality in scripts, YaST provides command line support for individual modules. However, not all modules have command line support. To display the available options of a module, use the following command:

> sudo yast module_name help

If a module does not provide command line support, it is started in a text mode with the following message:

This YaST module does not support the command line interface.

The following sections describe all YaST modules with command line support, along with a brief explanation of all their commands and available options.

4.4.3.1 Common YaST module commands

All YaST modules support the following commands:

help

Lists all the module's supported commands with their description:

> sudo yast lan help
longhelp

Same as help, but adds a detailed list of all command's options and their descriptions:

> sudo yast lan longhelp
xmlhelp

Same as longhelp, but the output is structured as an XML document and redirected to a file:

> sudo yast lan xmlhelp xmlfile=/tmp/yast_lan.xml
interactive

Enters the interactive mode. This lets you run the module's commands without prefixing them with sudo yast. Use exit to leave the interactive mode.

4.4.3.2 yast add-on

Adds a new add-on product from the specified path:

 > sudo yast add-on http://server.name/directory/Lang-AddOn-CD1/

You can use the following protocols to specify the source path: http:// ftp:// nfs:// disk:// cd:// or dvd://.

4.4.3.3 yast audit-laf

Displays and configures the Linux Audit Framework. Refer to the Book “Security and Hardening Guide” for more details. yast audit-laf accepts the following commands:

set

Sets an option:

> sudo yast audit-laf set log_file=/tmp/audit.log

For a complete list of options, run yast audit-laf set help.

show

Displays settings of an option:

> sudo yast audit-laf show diskspace
space_left: 75
space_left_action: SYSLOG
admin_space_left: 50
admin_space_left_action: SUSPEND
action_mail_acct: root
disk_full_action: SUSPEND
disk_error_action: SUSPEND

For a complete list of options, run yast audit-laf show help.

4.4.3.4 yast dhcp-server

Manages the DHCP server and configures its settings. yast dhcp-server accepts the following commands:

disable

Disables the DHCP server service.

enable

Enables the DHCP server service.

host

Configures settings for individual hosts.

interface

Specifies to which network interface to listen to:

> sudo yast dhcp-server interface current
Selected Interfaces: eth0
Other Interfaces: bond0, pbu, eth1

For a complete list of options, run yast dhcp-server interface help.

options

Manages global DHCP options. For a complete list of options, run yast dhcp-server options help.

status

Prints the status of the DHCP service.

subnet

Manages the DHCP subnet options. For a complete list of options, run yast dhcp-server subnet help.

4.4.3.5 yast dns-server

Manages the DNS server configuration. yast dns-server accepts the following commands:

acls

Displays access control list settings:

 > sudo yast dns-server acls show
 ACLs:
 -----
  Name       Type        Value
  ----------------------------
  any        Predefined
  localips   Predefined
  localnets  Predefined
  none       Predefined
dnsrecord

Configures zone resource records:

> sudo yast dnsrecord add zone=example.org query=office.example.org type=NS value=ns3

For a complete list of options, run yast dns-server dnsrecord help.

forwarders

Configures DNS forwarders:

> sudo yast dns-server forwarders add ip=10.0.0.100
> sudo yast dns-server forwarders show
[...]
Forwarder IP
------------
10.0.0.100

For a complete list of options, run yast dns-server forwarders help.

host

Handles 'A' and its related 'PTR' record at once:

> sudo yast dns-server host show zone=example.org

For a complete list of options, run yast dns-server host help.

logging

Configures logging settings:

> sudo yast dns-server logging set updates=no transfers=yes

For a complete list of options, run yast dns-server logging help.

mailserver

Configures zone mail servers:

> sudo yast dns-server mailserver add zone=example.org mx=mx1 priority=100

For a complete list of options, run yast dns-server mailserver help.

nameserver

Configures zone name servers:

> sudo yast dns-server nameserver add zone=example.com ns=ns1

For a complete list of options, run yast dns-server nameserver help.

soa

Configures the start of authority (SOA) record:

> sudo yast dns-server soa set zone=example.org serial=2006081623 ttl=2D3H20S

For a complete list of options, run yast dns-server soa help.

startup

Manages the DNS server service:

> sudo yast dns-server startup atboot

For a complete list of options, run yast dns-server startup help.

transport

Configures zone transport rules. For a complete list of options, run yast dns-server transport help.

zones

Manages DNS zones:

> sudo yast dns-server zones add name=example.org zonetype=master

For a complete list of options, run yast dns-server zones help.

4.4.3.6 yast disk

Prints information about all disks or partitions. The only supported command is list followed by either of the following options:

disks

Lists all configured disks in the system:

> sudo yast disk list disks
Device   | Size       | FS Type | Mount Point | Label | Model
---------+------------+---------+-------------+-------+-------------
/dev/sda | 119.24 GiB |         |             |       | SSD 840
/dev/sdb |  60.84 GiB |         |             |       | WD1003FBYX-0
partitions

Lists all partitions in the system:

> sudo yast disk list partitions
Device         | Size       | FS Type | Mount Point | Label | Model
---------------+------------+---------+-------------+-------+------
/dev/sda1      |   1.00 GiB | Ext2    | /boot       |       |
/dev/sdb1      |   1.00 GiB | Swap    | swap        |       |
/dev/sdc1      | 698.64 GiB | XFS     | /mnt/extra  |       |
/dev/vg00/home | 580.50 GiB | Ext3    | /home       |       |
/dev/vg00/root | 100.00 GiB | Ext3    | /           |       |
[...]

4.4.3.7 yast ftp-server

Configures FTP server settings. yast ftp-server accepts the following options:

SSL, TLS

Controls secure connections via SSL and TLS. SSL options are valid for the vsftpd only.

> sudo yast ftp-server SSL enable
> sudo yast ftp-server TLS disable
access

Configures access permissions:

> sudo yast ftp-server access authen_only

For a complete list of options, run yast ftp-server access help.

anon_access

Configures access permissions for anonymous users:

> sudo yast ftp-server anon_access can_upload

For a complete list of options, run yast ftp-server anon_access help.

anon_dir

Specifies the directory for anonymous users. The directory must already exist on the server:

> sudo yast ftp-server anon_dir set_anon_dir=/srv/ftp

For a complete list of options, run yast ftp-server anon_dir help.

chroot

Controls change root environment (chroot):

> sudo yast ftp-server chroot enable
> sudo yast ftp-server chroot disable
idle-time

Sets the maximum idle time in minutes before FTP server terminates the current connection:

> sudo yast ftp-server idle-time set_idle_time=15
logging

Determines whether to save the log messages into a log file:

> sudo yast ftp-server logging enable
> sudo yast ftp-server logging disable
max_clients

Specifies the maximum number of concurrently connected clients:

> sudo yast ftp-server max_clients set_max_clients=1500
max_clients_ip

Specifies the maximum number of concurrently connected clients via IP:

> sudo yast ftp-server max_clients_ip set_max_clients=20
max_rate_anon

Specifies the maximum data transfer rate permitted for anonymous clients (KB/s):

> sudo yast ftp-server max_rate_anon set_max_rate=10000
max_rate_authen

Specifies the maximum data transfer rate permitted for locally authenticated users (KB/s):

> sudo yast ftp-server max_rate_authen set_max_rate=10000
port_range

Specifies the port range for passive connection replies:

> sudo yast ftp-server port_range set_min_port=20000 set_max_port=30000

For a complete list of options, run yast ftp-server port_range help.

show

Displays FTP server settings.

startup

Controls the FTP start-up method:

> sudo yast ftp-server startup atboot

For a complete list of options, run yast ftp-server startup help.

umask

Specifies the file umask for authenticated:anonymous users:

> sudo yast ftp-server umask set_umask=177:077
welcome_message

Specifies the text to display when someone connects to the FTP server:

> sudo yast ftp-server welcome_message set_message="hello everybody"

4.4.3.8 yast http-server

Configures the HTTP server (Apache2). yast http-server accepts the following commands:

configure

Configures the HTTP server host settings:

> sudo yast http-server configure host=main servername=www.example.com \
 serveradmin=admin@example.com

For a complete list of options, run yast http-server configure help.

hosts

Configures virtual hosts:

> sudo yast http-server hosts create servername=www.example.com \
 serveradmin=admin@example.com documentroot=/var/www

For a complete list of options, run yast http-server hosts help.

listen

Specifies the ports and network addresses where the HTTP server should listen:

> sudo yast http-server listen add=81
> sudo yast http-server listen list
Listen Statements:
==================
:80
:81
> sudo yast http-server delete=80

For a complete list of options, run yast http-server listen help.

mode

Enables or disables the wizard mode:

> sudo yast http-server mode wizard=on
modules

Controls the Apache2 server modules:

> sudo yast http-server modules enable=php5,rewrite
> sudo yast http-server modules disable=ssl
> sudo http-server modules list
[...]
Enabled rewrite
Disabled ssl
Enabled php5
[...]

4.4.3.9 yast kdump

Configures kdump settings. For more information on kdump, refer to the Book “System Analysis and Tuning Guide”, Chapter 19 “Kexec and Kdump”, Section 19.7 “Basic Kdump configuration”. yast kdump accepts the following commands:

copykernel

Copies the kernel into the dump directory.

customkernel

Specifies the kernel_string part of the name of the custom kernel. The naming scheme is /boot/vmlinu[zx]-kernel_string[.gz].

> sudo yast kdump customkernel kernel=kdump

For a complete list of options, run yast kdump customkernel help.

dumpformat

Specifies the (compression) format of the dump kernel image. Available formats are none, ELF, compressed or lzo:

> sudo yast kdump dumpformat dump_format=ELF
dumplevel

Specifies the dump level number in the range from 0 to 31:

> sudo yast kdump dumplevel dump_level=24
dumptarget

Specifies the destination for saving dump images:

> sudo kdump dumptarget target=ssh server=name_server port=22 \
 dir=/var/log/dump user=user_name

For a complete list of options, run yast kdump dumptarget help.

immediatereboot

Controls whether the system should reboot immediately after saving the core in the Kdump kernel:

> sudo yast kdump immediatereboot enable
> sudo yast kdump immediatereboot disable
keepolddumps

Specifies how many old dump images are kept. Specify zero to keep them all:

> sudo yast kdump keepolddumps no=5
kernelcommandline

Specifies the command line that needs to be passed off to the kdump kernel:

> sudo yast kdump kernelcommandline command="ro root=LABEL=/"
kernelcommandlineappend

Specifies the command line that you need to append to the default command line string:

> sudo yast kdump kernelcommandlineappend command="ro root=LABEL=/"
notificationcc

Specifies an e-mail address for sending copies of notification messages:

> sudo yast kdump notificationcc email="user1@example.com user2@example.com"
notificationto

Specifies an e-mail address for sending notification messages:

> sudo yast kdump notificationto email="user1@example.com user2@example.com"
show

Displays kdump settings:

> sudo yast kdump show
Kdump is disabled
Dump Level: 31
Dump Format: compressed
Dump Target Settings
target: file
file directory: /var/crash
Kdump immediate reboots: Enabled
Numbers of old dumps: 5
smtppass

Specifies the file with the plain text SMTP password used for sending notification messages:

> sudo yast kdump smtppass pass=/path/to/file
smtpserver

Specifies the SMTP server host name used for sending notification messages:

> sudo yast kdump smtpserver server=smtp.server.com
smtpuser

Specifies the SMTP user name used for sending notification messages:

> sudo yast kdump smtpuser user=smtp_user
startup

Enables or disables start-up options:

> sudo yast kdump startup enable alloc_mem=128,256
> sudo yast kdump startup disable

4.4.3.10 yast keyboard

Configures the system keyboard for virtual consoles. It does not affect the keyboard settings in graphical desktop environments, such as GNOME or KDE. yast keyboard accepts the following commands:

list

Lists all available keyboard layouts.

set

Activates new keyboard layout setting:

> sudo yast keyboard set layout=czech
summary

Displays the current keyboard configuration.

4.4.3.11 yast lan

Configures network cards. yast lan accepts the following commands:

add

Configures a new network card:

> sudo yast lan add name=vlan50 ethdevice=eth0 bootproto=dhcp

For a complete list of options, run yast lan add help.

delete

Deletes an existing network card:

> sudo yast lan delete id=0
edit

Changes the configuration of an existing network card:

> sudo yast lan edit id=0 bootproto=dhcp
list

Displays a summary of network card configuration:

> sudo yast lan list
id name,           bootproto
0 Ethernet Card 0, NONE
1 Network Bridge,  DHCP

4.4.3.12 yast language

Configures system languages. yast language accepts the following commands:

list

Lists all available languages.

set

Specifies the main system languages and secondary languages:

> sudo yast language set lang=cs_CZ languages=en_US,es_ES no_packages

4.4.3.13 yast mail

Displays the configuration of the mail system:

> sudo yast mail summary

4.4.3.14 yast nfs

Controls the NFS client. yast nfs accepts the following commands:

add

Adds a new NFS mount:

> sudo yast nfs add spec=remote_host:/path/to/nfs/share file=/local/mount/point

For a complete list of options, run yast nfs add help.

delete

Deletes an existing NFS mount:

> sudo yast nfs delete spec=remote_host:/path/to/nfs/share file=/local/mount/point

For a complete list of options, run yast nfs delete help.

edit

Changes an existing NFS mount:

> sudo yast nfs edit spec=remote_host:/path/to/nfs/share \
 file=/local/mount/point type=nfs4

For a complete list of options, run yast nfs edit help.

list

Lists existing NFS mounts:

> sudo yast nfs list
Server            Remote File System    Mount Point    Options
----------------------------------------------------------------
nfs.example.com   /mnt                  /nfs/mnt       nfs
nfs.example.com   /home/tux/nfs_share   /nfs/tux       nfs

4.4.3.15 yast nfs-server

Configures the NFS server. yast nfs-server accepts the following commands:

add

Adds a directory to export:

> sudo yast nfs-server add mountpoint=/nfs/export hosts=*.allowed_hosts.com

For a complete list of options, run yast nfs-server add help.

delete

Deletes a directory from the NFS export:

 > sudo yast nfs-server delete mountpoint=/nfs/export
set

Specifies additional parameters for the NFS server:

> sudo yast nfs-server set enablev4=yes security=yes

For a complete list of options, run yast nfs-server set help.

start

Starts the NFS server service:

> sudo yast nfs-server start
stop

Stops the NFS server service:

> sudo yast nfs-server stop
summary

Displays a summary of the NFS server configuration:

> sudo yast nfs-server summary
NFS server is enabled
NFS Exports
* /mnt
* /home

NFSv4 support is enabled.
The NFSv4 domain for idmapping is localdomain.
NFS Security using GSS is enabled.

4.4.3.16 yast nis

Configures the NIS client. yast nis accepts the following commands:

configure

Changes global settings of a NIS client:

> sudo yast nis configure server=nis.example.com broadcast=yes

For a complete list of options, run yast nis configure help.

disable

Disables the NIS client:

> sudo yast nis disable
enable

Enables your machine as NIS client:

> sudo yast nis enable server=nis.example.com broadcast=yes automounter=yes

For a complete list of options, run yast nis enable help.

find

Shows available NIS servers for a given domain:

> sudo yast nis find domain=nisdomain.com
summary

Displays a configuration summary of a NIS client.

4.4.3.17 yast nis-server

Configures a NIS server. yast nis-server accepts the following commands:

master

Configures a NIS master server:

> sudo yast nis-server master domain=nisdomain.com yppasswd=yes

For a complete list of options, run yast nis-server master help.

slave

Configures a NIS worker server:

> sudo yast nis-server slave domain=nisdomain.com master_ip=10.100.51.65

For a complete list of options, run yast nis-server slave help.

stop

Stops a NIS server:

> sudo yast nis-server stop
summary

Displays a configuration summary of a NIS server:

> sudo yast nis-server summary

4.4.3.18 yast proxy

Configures proxy settings. yast proxy accepts the following commands:

authentication

Specifies the authentication options for proxy:

> sudo yast proxy authentication username=tux password=secret

For a complete list of options, run yast proxy authentication help.

enable, disable

Enables or disables proxy settings.

set

Changes the current proxy settings:

> sudo yast proxy set https=proxy.example.com

For a complete list of options, run yast proxy set help.

summary

Displays proxy settings.

4.4.3.19 yast rdp

Controls remote desktop settings. yast rdp accepts the following commands:

allow

Allows remote access to the server's desktop:

> sudo yast rdp allow set=yes
list

Displays the remote desktop configuration summary.

4.4.3.20 yast samba-client

Configures the Samba client settings. yast samba-client accepts the following commands:

configure

Changes global settings of Samba:

> sudo yast samba-client configure workgroup=FAMILY
isdomainmember

Checks whether the machine is a member of a domain:

> sudo yast samba-client isdomainmember domain=SMB_DOMAIN
joindomain

Makes the machine a member of a domain:

> sudo yast samba-client joindomain domain=SMB_DOMAIN user=username password=pwd
winbind

Enables or disables Winbind services (the winbindd daemon):

> sudo yast samba-client winbind enable
> sudo yast samba-client winbind disable

4.4.3.21 yast samba-server

Configures Samba server settings. yast samba-server accepts the following commands:

backend

Specifies the back-end for storing user information:

> sudo yast samba-server backend smbpasswd

For a complete list of options, run yast samba-server backend help.

configure

Configures global settings of the Samba server:

> sudo yast samba-server configure workgroup=FAMILY description='Home server'

For a complete list of options, run yast samba-server configure help.

list

Displays a list of available shares:

> sudo yast samba-server list
Status     Type Name
==============================
Disabled   Disk profiles
Enabled    Disk print$
Enabled    Disk homes
Disabled   Disk groups
Enabled    Disk movies
Enabled    Printer printers
role

Specifies the role of the Samba server:

> sudo yast samba-server role standalone

For a complete list of options, run yast samba-server role help.

service

Enables or disables the Samba services (smb and nmb):

> sudo yast samba-server service enable
> sudo yast samba-server service disable
share

Manipulates a single Samba share:

> sudo yast samba-server share name=movies browseable=yes guest_ok=yes

For a complete list of options, run yast samba-server share help.

4.4.3.22 yast security

Controls the security level of the host. yast security accepts the following commands:

level

Specifies the security level of the host:

> sudo yast security level server

For a complete list of options, run yast security level help.

set

Sets the value of a specific option:

> sudo yast security set passwd=sha512 crack=yes

For a complete list of options, run yast security set help.

summary

Displays a summary of the current security configuration:

sudoyast security summary

4.4.3.23 yast sound

Configures sound card settings. yast sound accepts the following commands:

add

Configures a new sound card. Without any parameters, the command adds the first detected card.

> sudo yast sound add card=0 volume=75

For a complete list of options, run yast sound add help.

channels

Lists available volume channels of a sound card:

> sudo yast sound channels card=0
Master 75
PCM 100
modules

Lists all available sound kernel modules:

> sudo yast sound modules
snd-atiixp ATI IXP AC97 controller (snd-atiixp)
snd-atiixp-modem ATI IXP MC97 controller (snd-atiixp-modem)
snd-virtuoso Asus Virtuoso driver (snd-virtuoso)
[...]
playtest

Plays a test sound on a sound card:

> sudo yast sound playtest card=0
remove

Removes a configured sound card:

> sudo yast sound remove card=0
> sudo yast sound remove all
set

Specifies new values for a sound card:

> sudo yast sound set card=0 volume=80
show

Displays detailed information about a sound card:

> sudo yast sound show card=0
Parameters of card 'ThinkPad X240' (using module snd-hda-intel):

align_buffer_size
 Force buffer and period sizes to be multiple of 128 bytes.
bdl_pos_adj
 BDL position adjustment offset.
beep_mode
 Select HDA Beep registration mode (0=off, 1=on) (default=1).
 Default Value: 0
enable_msi
 Enable Message Signaled Interrupt (MSI)
[...]
summary

Prints a configuration summary for all sound cards on the system:

> sudo yast sound summary
volume

Specifies the volume level of a sound card:

sudoyast sound volume card=0 play

4.4.3.24 yast sysconfig

Controls the variables in files under /etc/sysconfig. yast sysconfig accepts the following commands:

clear

Sets empty value to a variable:

> sudo yast sysconfig clear=POSTFIX_LISTEN
Tip
Tip: Variable in multiple files

If the variable is available in several files, use the VARIABLE_NAME$FILE_NAME syntax:

> sudo yast sysconfig clear=CONFIG_TYPE$/etc/sysconfig/mail
details

Displays detailed information about a variable:

> sudo yast sysconfig details variable=POSTFIX_LISTEN
Description:
Value:
File: /etc/sysconfig/postfix
Possible Values: Any value
Default Value:
Configuration Script: postfix
Description:
 Comma separated list of IP's
 NOTE: If not set, LISTEN on all interfaces
list

Displays summary of modified variables. Use all to list all variables and their values:

> sudo yast sysconfig list all
AOU_AUTO_AGREE_WITH_LICENSES="false"
AOU_ENABLE_CRONJOB="true"
AOU_INCLUDE_RECOMMENDS="false"
[...]
set

Sets a value for a variable:

> sudo yast sysconfig set DISPLAYMANAGER=gdm
Tip
Tip: Variable in multiple files

If the variable is available in several files, use the VARIABLE_NAME$FILE_NAME syntax:

> sudo yast sysconfig set CONFIG_TYPE$/etc/sysconfig/mail=advanced

4.4.3.25 yast tftp-server

Configures a TFTP server. yast tftp-server accepts the following commands:

directory

Specifies the directory of the TFTP server:

> sudo yast tftp-server directory path=/srv/tftp
> sudo yast tftp-server directory list
Directory Path: /srv/tftp
status

Controls the status of the TFTP server service:

> sudo yast tftp-server status disable
> sudo yast tftp-server status show
Service Status: false
> sudo yast tftp-server status enable

4.4.3.26 yast timezone

Configures the time zone. yast timezone accepts the following commands:

list

Lists all available time zones grouped by region:

> sudo yast timezone list
Region: Africa
Africa/Abidjan (Abidjan)
Africa/Accra (Accra)
Africa/Addis_Ababa (Addis Ababa)
[...]
set

Specifies new values for the time zone configuration:

> sudo yast timezone set timezone=Europe/Prague hwclock=local
summary

Displays the time zone configuration summary:

> sudo yast timezone summary
Current Time Zone: Europe/Prague
Hardware Clock Set To: Local time
Current Time and Date: Mon 12. March 2018, 11:36:21 CET

4.4.3.27 yast users

Manages user accounts. yast users accepts the following commands:

add

Adds a new user:

> sudo yast users add username=user1 password=secret home=/home/user1

For a complete list of options, run yast users add help.

delete

Deletes an existing user account:

> sudo yast users delete username=user1 delete_home

For a complete list of options, run yast users delete help.

edit

Changes an existing user account:

> sudo yast users edit username=user1 password=new_secret

For a complete list of options, run yast users edit help.

list

Lists existing users filtered by user type:

> sudo yast users list system

For a complete list of options, run yast users list help.

show

Displays details about a user:

> sudo yast users show username=wwwrun
Full Name: WWW daemon apache
List of Groups: www
Default Group: wwwrun
Home Directory: /var/lib/wwwrun
Login Shell: /sbin/nologin
Login Name: wwwrun
UID: 456

For a complete list of options, run yast users show help.

5 Changing language and country settings with YaST

This chapter explains how to configure language and country settings. You can change the language globally for the whole system, individually for certain users or desktops, or temporarily for single applications. Additionally, you can configure secondary languages and adjust the date and country settings.

If you work in different countries or in a multilingual environment, you should configure your system accordingly. SUSE® Linux Enterprise Server can handle different locales in parallel. A locale is a set of parameters that defines the language and country settings reflected in the user interface.

The main system language is selected during installation, and keyboard and time zone settings are adjusted accordingly. However, you can install additional languages and determine which of the installed languages should be the default.

For those tasks, use the YaST language module as described in Section 5.1, “Changing the system language”. Install secondary languages to get optional localization if you need to start applications or desktops in languages other than the primary one.

The YaST time zone module allows you to adjust your country and time zone settings accordingly. It also lets you synchronize your system clock against a time server. For details, refer to Section 5.2, “Changing the country and time settings”.

5.1 Changing the system language

Depending on how you use your desktop and whether you want to switch the entire system to another language or only the desktop environment, you have several options:

Changing the system language globally

Proceed as described in Section 5.1.1, “Modifying system languages with YaST” and Section 5.1.2, “Switching the default system language” to install additional localized packages with YaST and to set the default language. Changes are effective after the next login. To ensure that the entire system reflects the change, reboot the system or close and restart all running services, applications and programs.

Changing the language for the desktop only

Provided you have previously installed the desired language packages for your desktop environment with YaST as described below, you can switch the language of your desktop using the desktop's control center. After the X server has been restarted, your entire desktop reflects your new choice of language. Applications not belonging to your desktop framework are not affected by this change and may still appear in the language that was set in YaST.

Temporarily switching languages for one application only

You can also run a single application in another language (that has already been installed with YaST). To do so, start it from the command line by specifying the language code as described in Section 5.1.3, “Switching languages for standard X and GNOME applications”.

5.1.1 Modifying system languages with YaST

YaST supports two different language categories:

Primary Language

The primary language set in YaST applies to the entire system, including YaST and the desktop environment. This language is used whenever available unless you manually specify another language.

Secondary Languages

Install secondary languages to make your system multilingual. Languages installed as secondary can be selected manually, when needed. For example, use a secondary language to start an application in a certain language to do word processing in this language.

Before installing additional languages, determine which of them should be the default system language (primary language).

To access the YaST language module, start YaST and click System › Language. Alternatively, start the Languages dialog directly by running sudo yast2 language & from a command line.

Image
Procedure 5.1: Installing additional languages

When installing additional languages, YaST allows you to set different locale settings for the user root, see Step 4. The option Locale Settings for User root determines how the locale variables (LC_*) in the file /etc/sysconfig/language are set for root. You can set them to the same locale as for regular users. Alternatively, you can keep them unaffected by any language changes, or only set the variable RC_LC_CTYPE to the same values as for the regular users. The RC_LC_CTYPE variable sets the localization for language-specific function calls.

  1. To add languages in the YaST language module, select the Secondary Languages you want to install.

  2. To make a language the default language, set it as Primary Language.

  3. Additionally, adapt the keyboard to the new primary language and adjust the time zone, if appropriate.

    Tip
    Tip: Advanced settings

    For advanced keyboard or time zone settings, select Hardware › System Keyboard Layout or System › Date and Time in YaST. For more information, refer to Chapter 32, Setting up your system keyboard layout and Section 5.2, “Changing the country and time settings”.

  4. To change language settings specific to the user root, click Details.

    1. Set Locale Settings for User root to the desired value. For more information, click Help.

    2. Decide whether to use Use UTF-8 Encoding for root or not.

  5. If your locale was not included in the list of primary languages available, try specifying it with Detailed Locale Setting. However, this may result in certain locales being incomplete.

  6. Confirm the changes in the dialogs with OK. If you have selected secondary languages, YaST installs the localized software packages for the additional languages.

The system is now multilingual. However, to start an application in a language other than the primary one, you need to set the desired language explicitly as explained in Section 5.1.3, “Switching languages for standard X and GNOME applications”.

5.1.2 Switching the default system language

To globally change the default language of a system, use the following procedure:

  1. Start the YaST language module.

  2. Select the desired new system language as Primary Language.

    Important
    Important: Deleting former system languages

    If you switch to a different primary language, the localized software packages for the former primary language gets removed from the system. To switch the default system language but keep the former primary language as an additional language, add it as Secondary Language by selecting the respective check box.

  3. Adjust the keyboard and time zone options as desired.

  4. Confirm your changes with OK.

  5. After YaST has applied the changes, restart current X sessions (for example, by logging out and logging in again) to make YaST and the desktop applications reflect your new language settings.

5.1.3 Switching languages for standard X and GNOME applications

After you have installed the respective language with YaST, you can run a single application in another language.

Start the application from the command line by using the following command:

LANG=LANGUAGE application

For example, to start f-spot in German, run LANG=de_DE f-spot. For other languages, use the appropriate language code. Get a list of all language codes available with the locale  -av command.

5.2 Changing the country and time settings

Using the YaST date and time module, adjust your system date, clock and time zone information to the area you are working in. To access the YaST module, start YaST and click System › Date and Time. Alternatively, start the Clock and Time Zone dialog directly by running sudo yast2 timezone & from a command line.

Image

First, select a general region, such as Europe. Choose an appropriate country that matches the one you are working in, for example, Germany.

Depending on which operating systems run on your workstation, adjust the hardware clock settings accordingly:

  • If you run another operating system on your machine, such as Microsoft Windows*, your system may not use UTC, but local time. In this case, deactivate Hardware Clock Set To UTC.

  • If you only run Linux on your machine, set the hardware clock to UTC and have the switch from standard time to daylight saving time performed automatically.

Important
Important: Set the hardware clock to UTC

The switch from standard time to daylight saving time (and vice versa) can only be performed automatically when the hardware clock (CMOS clock) is set to UTC. This also applies if you use automatic time synchronization with NTP, because automatic synchronization will only be performed if the time difference between the hardware and system clock is less than 15 minutes.

Since a wrong system time can cause serious problems (missed backups, dropped mail messages, mount failures on remote file systems, etc.) it is strongly recommended to always set the hardware clock to UTC.

You can change the date and time manually or opt for synchronizing your machine against an NTP server, either permanently or only for adjusting your hardware clock.

Procedure 5.2: Manually adjusting time and date
  1. In the YaST timezone module, click Other Settings to set date and time.

  2. Select Manually and enter date and time values.

  3. Confirm your changes.

Procedure 5.3: Setting date and time with NTP server
  1. Click Other Settings to set date and time.

  2. Select Synchronize with NTP Server.

  3. Enter the address of an NTP server, if not already populated.

    Image
  4. With the Configure button, you can open the advanced NTP configuration. For details, see Section 38.1, “Configuring an NTP client with YaST”.

  5. Confirm your changes.

6 Managing users with YaST

During installation, you may have created a local user for your system. With the YaST module User and Group Management you can add users or edit existing ones. It also lets you configure your system to authenticate users with a network server.

6.1 User and group administration dialog

To administer users or groups, start YaST and click Security and Users › User and Group Management. Alternatively, start the User and Group Administration dialog directly by running sudo yast2 users & from a command line.

YaST user and group administration
Figure 6.1: YaST user and group administration

Every user is assigned a system-wide user ID (UID). Apart from the users that can log in to your machine, there are also several system users for internal use only. Each user is assigned to one or more groups. Similar to system users, there are also system groups for internal use.

The main window shows several tabs, depending on the set of users (local users, network users, system users) you choose to view and modify. The tabs allow you to perform the following tasks:

Managing user accounts

From the Users tab create, modify, delete or temporarily disable user accounts as described in Section 6.2, “Managing user accounts”. Learn about advanced options like enforcing password policies, using encrypted home directories, or managing disk quotas in Section 6.3, “Additional options for user accounts”.

Changing default settings

Local user accounts are created according to the settings defined on the Defaults for New Users tab. Learn how to change the default group assignment, or the default path and access permissions for home directories in Section 6.4, “Changing default settings for local users”.

Assigning users to groups

Learn how to change the group assignment for individual users in Section 6.5, “Assigning users to groups”.

Managing groups

From the Groups tab, you can add, modify or delete existing groups. Refer to Section 6.6, “Managing groups” for information on how to do this.

Changing user authentication method

When your machine is connected to a network that provides user authentication methods like NIS or LDAP, you can choose between several authentication methods on the Authentication Settings tab. For more information, refer to Section 6.7, “Changing the user authentication method”.

For user and group management, the dialog provides similar functionality. You can easily switch between the user and group administration view by choosing the appropriate tab at the top of the dialog.

Filter options allow you to define the set of users or groups you want to modify: on the Users or Group tab, click Set Filter to view and edit users or groups. They are listed according to certain categories, such as Local Users or LDAP Users, if applicable. With Set Filter › Customize Filter you can also set up and use a custom filter.

Depending on the filter you choose, not all the following options and functions may be available from the dialog.

6.2 Managing user accounts

YaST allows you to create, modify, delete or temporarily disable user accounts. Do not modify user accounts unless you are an experienced user or administrator.

Note
Note: Changing user IDs of existing users

File ownership is bound to the user ID, not to the user name. After a user ID change, the files in the user's home directory are automatically adjusted to reflect this change. However, after an ID change, the user no longer owns the files they created elsewhere in the file system unless the file ownership for those files are manually modified.

The following instructions demonstrate how to set up default user accounts. For further options, refer to Section 6.3, “Additional options for user accounts”.

Procedure 6.1: Adding or modifying user accounts
  1. Open the YaST User and Group Administration dialog and click the Users tab.

  2. With Set Filter define the set of users you want to manage. The dialog lists users in the system and the groups the users belong to.

  3. To modify options for an existing user, select an entry and click Edit.

    To create a new user account, click Add.

  4. Enter the appropriate user data on the first tab, such as Username (which is used for login) and Password. This data is sufficient to create a new user. If you click OK now, the system automatically assigns a user ID and sets all other values as default.

  5. Activate Receive System Mail if you want system notifications to be delivered to this user's mailbox. This creates a mail alias for root and the user can read the system mail without having to first log in as root.

    The mails sent by system services are stored in the local mailbox /var/spool/mail/USERNAME, where USERNAME is the login name of the selected user. To read e-mails, you can use the mail command.

  6. To adjust further details such as the user ID or the path to the user's home directory, do so on the Details tab.

    If you need to relocate the home directory of an existing user, enter the path to the new home directory there and move the contents of the current home directory with Move to New Location. Otherwise, a new home directory is created without any of the existing data.

  7. To force users to regularly change their password or set other password options, switch to Password Settings and adjust the options. For more details, refer to Section 6.3.2, “Enforcing password policies”.

  8. If all options are set according to your wishes, click OK.

  9. Click OK to close the administration dialog and to save the changes. A newly added user can now log in to the system using the login name and password you created.

    Alternatively, to save all changes without exiting the User and Group Administration dialog, click Expert Options › Write Changes Now.

Warning
Warning: Do not rename the root account

While it is technically possible to rename the root account, certain applications, scripts or third-party products may rely on the existence of a user called root. While such a configuration always targets individual environments, necessary adjustments could be overwritten by vendor updates, so this becomes an ongoing task, not a one-time setting. This is especially true in very complex setups involving third-party applications, where it needs to be verified with every involved vendor whether a rename of the root account is supported.

As the implications for renaming the root account cannot be foreseen, SUSE does not support renaming the root account.

Usually, the idea behind renaming the root account is to hide it or make it unpredictable. However, /etc/passwd requires 644 permissions for regular users, so any user of the system can retrieve the login name for the user ID 0. For better ways to secure the root account, refer to Book “Security and Hardening Guide”, Chapter 14 “User management”, Section 14.5 “Restricting root logins” and Book “Security and Hardening Guide”, Chapter 14 “User management”, Section 14.5.3 “Restricting SSH logins”.

Tip
Tip: Matching user IDs

It is useful to match the (local) user ID to the ID in the network. For example, a new (local) user on a laptop should be integrated into a network environment with the same user ID. This ensures that the file ownership of the files the user creates offline is the same as if they had created them directly on the network.

Procedure 6.2: Disabling or deleting user accounts
  1. Open the YaST User and Group Administration dialog and click the Users tab.

  2. To temporarily disable a user account without deleting it, select the user from the list and click Edit. Activate Disable User Login. The user cannot log in to your machine until you enable the account again.

  3. To delete a user account, select the user from the list and click Delete. Choose if you also want to delete the user's home directory or to retain the data.

6.3 Additional options for user accounts

In addition to the settings for a default user account, SUSE® Linux Enterprise Server offers further options. For example, options to enforce password policies, use encrypted home directories or define disk quotas for users and groups.

6.3.1 Automatic login and passwordless login

If you use the GNOME desktop environment you can configure Auto Login for a certain user and Passwordless Login for all users. Auto login causes a user to become automatically logged in to the desktop environment on boot. This functionality can only be activated for one user at a time. Login without password allows all users to log in to the system after they have entered their user name in the login manager.

Warning
Warning: Security risk

Enabling Auto Login or Passwordless Login on a machine that can be accessed by more than one person is a security risk. Without the need to authenticate, any user can gain access to your system and your data. If your system contains confidential data, do not use this functionality.

To activate auto login or login without password, access these functions in the YaST User and Group Administration with Expert Options › Login Settings.

6.3.2 Enforcing password policies

On any system with multiple users, it is a good idea to enforce at least basic password security policies. Users should change their passwords regularly and use strong passwords that cannot easily be exploited. For local users, proceed as follows:

Procedure 6.3: Configuring password settings
  1. Open the YaST User and Group Administration dialog and select the Users tab.

  2. Select user and click Edit.

  3. Switch to the Password Settings tab. The user's last password change is displayed on the tab.

  4. To make the user change their password at next login, activate Force Password Change.

  5. To enforce password rotation, set a Maximum Number of Days for the Same Password and a Minimum Number of Days for the Same Password.

  6. To remind the user to change their password before it expires, set the number of Days before Password Expiration to Issue Warning.

  7. To restrict the period of time the user can log in after their password has expired, change the value in Days after Password Expires with Usable Login.

  8. You can also specify a certain expiration date for the complete account. Enter the Expiration Date in YYYY-MM-DD format. This setting is not password-related but rather applies to the account itself.

  9. For more information about options and default values, click Help.

  10. Apply your changes with OK.

6.3.3 Managing quotas

To prevent system capacities from being exhausted without notification, system administrators can set up quotas for users or groups. Quotas can be defined for one or more file systems and restrict the amount of disk space that can be used and the number of inodes (index nodes) that can be created there. Inodes are data structures on a file system that store basic information about a regular file, directory or other file system object. They store all attributes of a file system object (like user and group ownership, read, write or execute permissions), except file name and contents.

SUSE Linux Enterprise Server allows usage of soft and hard quotas. Additionally, grace intervals can be defined that allow users or groups to temporarily exceed their quotas by certain amounts.

Soft quota

Defines a warning level at which users are informed that they are nearing their limit. Administrators may urge the users to clean up and reduce their data on the partition. The soft quota limit is normally lower than the hard quota limit.

Hard quota

Defines the limit at which write requests are denied. When the hard quota is reached, no more data can be stored and applications may crash.

Grace period

Defines the time between the overflow of the soft quota and a warning being issued. Normally set to a rather low value of one or several hours.

Procedure 6.4: Enabling quota support for a partition

To configure quotas for certain users and groups, you need to enable quota support for the respective partition in the YaST Expert Partitioner first.

Note
Note: Quotas for Btrfs partitions

Quotas for Btrfs partitions are handled differently. For more information, see Book “Storage Administration Guide”, Chapter 1 “Overview of file systems in Linux”, Section 1.2.5 “Btrfs quota support for subvolumes”.

  1. In YaST, select System › Partitioner and click Yes to proceed.

  2. In the Expert Partitioner, select the partition for which to enable quotas and click Edit.

  3. Click Fstab Options and activate Enable Quota Support. If the quota package is not already installed, it will be installed when you confirm the respective message with Yes.

  4. Confirm your changes and leave the Expert Partitioner.

  5. Make sure the service quotaon is running by entering the following command:

    > sudo systemctl status quotaon.service

    It should be marked as being active. If this is not the case, start it with the command systemctl start quotaon.service.

Procedure 6.5: Setting up quotas for users or groups

Now you can define soft or hard quotas for specific users or groups and set time periods as grace intervals.

  1. In the YaST User and Group Administration, select the user or the group you want to set the quotas for and click Edit.

  2. On the Plug-Ins tab, select the Manage User Quota entry and click Launch to open the Quota Configuration dialog.

  3. From File System, select the partition to which the quota should apply.

    Image
  4. Below Size Limits, restrict the amount of disk space. Enter the number of 1 KB blocks the user or group may have on this partition. Specify a Soft Limit and a Hard Limit value.

  5. Additionally, you can restrict the number of inodes the user or group may have on the partition. Below Inodes Limits, enter a Soft Limit and Hard Limit.

  6. You can only define grace intervals if the user or group has already exceeded the soft limit specified for size or inodes. Otherwise, the time-related text boxes are not activated. Specify the time period for which the user or group is allowed to exceed the limits set above.

  7. Confirm your settings with OK.

  8. Click OK to close the administration dialog and save the changes.

    Alternatively, to save all changes without exiting the User and Group Administration dialog, click Expert Options › Write Changes Now.

SUSE Linux Enterprise Server also ships command line tools like repquota or warnquota. System administrators can use these tools to control the disk usage or send e-mail notifications to users exceeding their quota. Using quota_nld, administrators can also forward kernel messages about exceeded quotas to D-BUS. For more information, refer to the repquota, the warnquota and the quota_nld man page.

6.4 Changing default settings for local users

When creating new local users, several default settings are used by YaST. These include, for example, the group the user belongs to, or the access permissions of the user's home directory. You can change these default settings to meet your requirements:

  1. Open the YaST User and Group Administration dialog and select the Defaults for New Users tab.

  2. To change the group the new users should automatically belong to, select another group from Default Group.

  3. If you do not want to use /home/USERNAME as the default path for new users' home directories, modify the Path Prefix for Home Directory.

  4. To change the default permission modes for newly created home directories, adjust the umask value in Umask for Home Directory. For more information about umask, refer to Book “Security and Hardening Guide”, Chapter 19 “Access control lists in Linux” and to the umask man page.

  5. For information about the individual options, click Help.

  6. Apply your changes with OK.

6.5 Assigning users to groups

Local users are assigned to several groups according to the default settings, which you can access from the User and Group Administration dialog on the Defaults for New Users tab. In the following, learn how to modify an individual user's group assignment. If you need to change the default group assignments for new users, refer to Section 6.4, “Changing default settings for local users”.

Procedure 6.6: Changing a user's group assignment
  1. Open the YaST User and Group Administration dialog and click the Users tab. It lists users and the groups the users belong to.

  2. Click Edit and switch to the Details tab.

  3. To change the group the user belongs to, click Default Group and select the group from the list.

  4. To assign the user additional secondary groups, activate the corresponding check boxes in the Additional Groups list.

  5. Click OK to apply your changes.

  6. Click OK to close the administration dialog and save the changes.

    Alternatively, to save all changes without exiting the User and Group Administration dialog, click Expert Options › Write Changes Now.

6.6 Managing groups

With YaST you can also easily add, modify or delete groups.

Procedure 6.7: Creating and modifying groups
  1. Open the YaST User and Group Management dialog and click the Groups tab.

  2. With Set Filter define the set of groups you want to manage. The dialog lists groups in the system.

  3. To create a new group, click Add.

  4. To modify an existing group, select the group and click Edit.

  5. In the following dialog, enter or change the data. The list on the right shows an overview of all available users and system users which can be members of the group.

    Image
  6. To add existing users to a new group select them from the list of possible Group Members by checking the corresponding box. To remove them from the group deactivate the box.

  7. Click OK to apply your changes.

  8. Click OK to close the administration dialog and save the changes.

    Alternatively, to save all changes without exiting the User and Group Administration dialog, click Expert Options › Write Changes Now.

To delete a group, it must not contain any group members. To delete a group, select it from the list and click Delete. Click OK to close the administration dialog and save the changes. Alternatively, to save all changes without exiting the User and Group Administration dialog, click Expert Options › Write Changes Now.

6.7 Changing the user authentication method

When your machine is connected to a network, you can change the authentication method. The following options are available:

NIS

Users are administered centrally on a NIS server for all systems in the network. For details, see Book “Security and Hardening Guide”, Chapter 3 “Using NIS”.

SSSD

The System Security Services Daemon (SSSD) can locally cache user data and then allow users to use the data, even if the real directory service is (temporarily) unreachable. For details, see Book “Security and Hardening Guide”, Chapter 4 “Setting up authentication clients using YaST”, Section 4.2 “SSSD”.

Samba

SMB authentication is often used in mixed Linux and Windows networks. For details, see Book “Storage Administration Guide”, Chapter 20 “Samba” .

To change the authentication method, proceed as follows:

  1. Open the User and Group Administration dialog in YaST.

  2. Click the Authentication Settings tab to show an overview of the available authentication methods and the current settings.

  3. To change the authentication method, click Configure and select the authentication method you want to modify. This takes you directly to the client configuration modules in YaST. For information about the configuration of the appropriate client, refer to the following sections:

    NIS: Book “Security and Hardening Guide”, Chapter 3 “Using NIS”, Section 3.2 “Configuring NIS clients”

    LDAP: Book “Security and Hardening Guide”, Chapter 4 “Setting up authentication clients using YaST”, Section 4.1 “Configuring an authentication client with YaST”

    Samba: Book “Storage Administration Guide”, Chapter 20 “Samba”, Section 20.5.1 “Configuring a Samba client with YaST”

    SSSD: Book “Security and Hardening Guide”, Chapter 4 “Setting up authentication clients using YaST”, Section 4.2 “SSSD”

  4. After accepting the configuration, return to the User and Group Administration overview.

  5. Click OK to close the administration dialog.

6.8 Default system users

By default, SUSE Linux Enterprise Server creates user names, which cannot be deleted. These users are typically defined in the Linux Standard Base. The following list provides the common user names and their purpose:

Common user names installed by default
bin, daemon

Legacy user, included for compatibility with legacy applications. New applications should no longer use this user name.

gdm

Used by GNOME Display Manager (GDM) to provide graphical logins and manage local and remote displays.

lp

Used by the Printer daemon for Common Unix Printing System (CUPS).

mail

User reserved for mailer programs like sendmail or postfix.

man

Used by man to access man pages.

messagebus

Used to access D-Bus (desktop bus), a software bus for inter-process communication. Daemon is dbus-daemon.

nobody

User that owns no files and is in no privileged groups. Nowadays, its use is limited as it is recommended by Linux Standard Base to provide a separate user account for each daemon.

nscd

Used by the Name Service Caching Daemon. This daemon is a lookup service to improve performance with NIS and LDAP. Daemon is nscd.

polkitd

Used by the PolicyKit Authorization Framework, which defines and handles authorization requests for unprivileged processes. Daemon is polkitd.

postfix

Used by the Postfix mailer.

pulse

Used by the Pulseaudio sound server.

root

Used by the system administrator, providing all appropriate privileges.

rpc

Used by the rpcbind command, an RPC port mapper.

rtkit

Used by the rtkit package providing a D-Bus system service for real time scheduling mode.

salt

User for parallel remote execution provided by Salt. Daemon is named salt-master.

scard

User for communication with smart cards and readers. Daemon is named pcscd.

srvGeoClue

Used by the GeoClue D-Bus service to provide location information.

sshd

Used by the Secure Shell daemon (SSH) to ensure secured and encrypted communication over an insecure network.

statd

Used by the Network Status Monitor protocol (NSM), implemented in the rpc.statd daemon, to listen for reboot notifications.

systemd-coredump

Used by the /usr/lib/systemd/systemd-coredump command to acquire, save and process core dumps.

systemd-timesync

Used by the /usr/lib/systemd/systemd-timesyncd command to synchronize the local system clock with a remote Network Time Protocol (NTP) server.

6.9 Default system groups

By default, SLE creates multiple user groups that are used by system services. The following list describes examples of required and common optional groups.

root

Administrative group with all privileges.

bin

Included for compatibility with legacy applications. New applications should not use this group.

daemon

Previously used to limit daemons' access to the system. Daemons should run under their own UID/GID now to separate daemons from one another.

audio

Privileges for audio devices.

gdm

Privileges for the GNOME Display Manager.

chrony

Privileges for the time synchronization service.

kvm

Privileges for the QEMU machine emulator toolkit.

libvirt

Privileges for virtualization stack.

lp

Privileges for printer operation.

mail

Privileges for mail services.

man

Privileges specific to manual pages and the man command.

sshd

Privileges for SSH communication protocol daemon.

7 YaST online update

SUSE offers a continuous stream of software security updates for your product. By default, the update applet is used to keep your system up to date. Refer to Section 8.5, “The GNOME package updater” for further information on the update applet. This chapter covers the alternative tool for updating software packages: YaST Online Update.

The current patches for SUSE® Linux Enterprise Server are available from an update software repository. If you have registered your product during the installation, an update repository is already configured. If you have not registered SUSE Linux Enterprise Server, you can do so by starting the Product Registration in YaST. Alternatively, you can manually add an update repository from a source you trust. To add or remove repositories, start the Repository Manager with Software › Software Repositories in YaST. Learn more about the Repository Manager in Section 8.4, “Managing software repositories and services”.

Note
Note: Error on accessing the update catalog

If you are not able to access the update catalog, this may happen because of an expired subscription. Normally, SUSE Linux Enterprise Server comes with a one-year or three-year subscription, during which you have access to the update catalog. This access will be denied after the subscription ends.

If an access to the update catalog is denied, you can see a warning message prompting you to visit the SUSE Customer Center and check your subscription. The SUSE Customer Center is available at https://scc.suse.com//.

Note
Note: Firewall settings for receiving updates

By default, the firewall on SUSE Linux Enterprise Server only blocks incoming connections. If your system is behind another firewall that blocks outgoing traffic, make sure to allow connections to https://scc.suse.com/ and https://updates.suse.com on ports 80 and 443 in order to receive updates.

SUSE provides updates with different relevance levels:

Security updates

Fix severe security hazards and should always be installed.

Recommended updates

Fix issues that could compromise your computer.

Optional updates

Fix non-security relevant issues or provide enhancements.

7.1 The online update dialog

To open the YaST Online Update dialog, start YaST and select Software  › Online Update. Alternatively, start it from the command line with yast2 online_update.

The Online Update window consists of four sections.

YaST online update
Figure 7.1: YaST online update

The Summary section on the left lists the available patches for SUSE Linux Enterprise Server. The patches are sorted by security relevance: security, recommended, and optional. You can change the view of the Summary section by selecting one of the following options from Show Patch Category:

Needed patches (default view)

Non-installed patches that apply to packages installed on your system.

Unneeded patches

Patches that either apply to packages not installed on your system, or patches that have requirements which have already have been fulfilled (because the relevant packages have already been updated from another source).

All patches

All patches available for SUSE Linux Enterprise Server.

Each list entry in the Summary section consists of a symbol and the patch name. For an overview of the possible symbols and their meaning, press ShiftF1. Actions required by Security and Recommended patches are automatically preset. These actions are Autoinstall, Autoupdate and Autodelete.

If you install an up-to-date package from a repository other than the update repository, the requirements of a patch for this package may be fulfilled with this installation. In this case a check mark is displayed in front of the patch summary. The patch is visible in the list until you mark it for installation. This does not install the patch (because the package already is up to date), but mark the patch as having been installed.

Select an entry in the Summary section to view a short Patch Description at the bottom left corner of the dialog. The upper right section lists the packages included in the selected patch (a patch can consist of several packages). Click an entry in the upper right section to view details about the respective package that is included in the patch.

7.2 Installing patches

The YaST Online Update dialog allows you to either install all available patches at once or manually select the desired patches. You may also revert patches that have been applied to the system.

By default, all new patches (except optional ones) that are currently available for your system are already marked for installation. They will be applied automatically once you click Accept or Apply. If one or multiple patches require a system reboot, you will be notified about this before the patch installation starts. You can then either decide to continue with the installation of the selected patches, skip the installation of all patches that need rebooting and install the rest, or go back to the manual patch selection.

Procedure 7.1: Applying patches with YaST online update
  1. Start YaST and select Software › Online Update.

  2. To automatically apply all new patches (except optional ones) that are currently available for your system, click Apply or Accept.

  3. First modify the selection of patches that you want to apply:

    1. Use the respective filters and views that the interface provides. For details, refer to Section 7.1, “The online update dialog”.

    2. Select or deselect patches according to your needs and wishes by right-clicking the patch and choosing the respective action from the context menu.

      Important
      Important: Always apply security updates

      Do not deselect any security-related patches without a good reason. These patches fix severe security hazards and prevent your system from being exploited.

    3. Most patches include updates for several packages. To change actions for single packages, right-click a package in the package view and choose an action.

    4. To confirm your selection and apply the selected patches, proceed with Apply or Accept.

  4. After the installation is complete, click Finish to leave the YaST Online Update. Your system is now up to date.

7.3 Viewing retracted patches

Maintenance updates are carefully tested to minimize the risk of introducing a bug. If a patch proves to contain a bug, it is automatically retracted. A new update (with a higher version number) is issued to revert the buggy patch, and is blocked from being installed again. You can see retracted patches, and their history, on the Package Classification tab.

Viewing retracted patches and history
Figure 7.2: Viewing retracted patches and history

7.4 Automatic online update

You may configure automatic updates with a daily, weekly or monthly schedule with YaST. Install the yast2-online-update-configuration package.

By default, updates are downloaded as delta RPMs. Since rebuilding RPM packages from delta RPMs is a memory- and processor-intensive task, certain setups or hardware configurations may require you to disable the use of delta RPMs for the sake of performance.

Some patches, such as kernel updates or packages requiring license agreements, require user interaction, which would cause the automatic update procedure to stop. You can configure skipping patches that require user interaction.

Use the Patches tab in the YaST Software module to review available and installed patches, including references to bug reports and CVE bulletins.

Procedure 7.2: Configuring the automatic online update
  1. After installation, start YaST and select Software › Online Update. Choose Configuration › Online Update. If the yast2-online-update-configuration is not installed, you will be prompted to do that.

    YaST online update configuration
    Figure 7.3: YaST online update configuration

    Alternatively, start the module with yast2 online_update_configuration from the command line.

  2. Choose the update interval: Daily, Weekly, or Monthly.

  3. Sometimes patches may require the attention of the administrator, for example when restarting critical services. For example, this might be an update for Docker Open Source Engine that requires all containers to be restarted. Before these patches are installed, the user is informed about the consequences and is asked to confirm the installation of the patch. Such patches are called Interactive Patches.

    When installing patches automatically, it is assumed that you have accepted the installation of interactive patches. If you prefer to review these patches before they get installed, check Skip Interactive Patches. In this case, interactive patches will be skipped during automated patching. Make sure to periodically run a manual online update, to check whether interactive patches are waiting to be installed.

  4. To automatically accept any license agreements, activate Agree with Licenses.

  5. To automatically install all packages recommended by updated packages, activate Include Recommended Packages.

  6. To disable the use of delta RPMs (for performance reasons), un-check Use Delta RPMs.

  7. To filter the patches by category (such as security or recommended), check Filter by Category and add the appropriate patch categories from the list. Only patches of the selected categories will be installed. It is a good practice to enable only automatic Security updates, and to manually review all others. Patching is normally reliable, but you may wish to test non-security patches, and roll them back if you encounter any problems.

    • Packagemanager and YaST supply patches for package management and YaST features and modules.

    • Security patches provide crucial updates and bugfixes.

    • Recommended patches are optional bugfixes and enhancements.

    • Optional are new packages.

    • Other is equivalent to miscellaneous.

    • Document is unused.

  8. Confirm your configuration by clicking OK.

The automatic online update does not automatically restart the system afterward. If there are package updates that require a system reboot, you need to do this manually.

8 Installing or removing software

Using YaST's software management module, you can search for software packages as well as install and remove them. When installing packages, YaST automatically resolves all dependencies. To install packages that are not on the installation medium, you can add software repositories and YaST to manage them. You can also keep your system up to date by managing software updates using the update applet.

The YaST Software Manager makes it possible to manage software sources on your system. There are two versions of this YaST module: a graphical version for X Window and a text-based version to use with the command line. The graphical flavor is described below—for details on the text-based YaST, see Chapter 4, YaST in text mode.

Note
Note: Confirmation and review of changes

When installing, updating, or removing packages, any changes in the Software Manager are only applied after clicking Accept or Apply. YaST maintains a list with all actions, allowing you to review and modify your changes before applying them to the system.

8.1 Definition of terms

The following terms are important for understanding installing and removing software in SUSE Linux Enterprise Server.

Repository

A local or remote directory containing packages, plus additional information about these packages (package metadata).

(Repository) alias/repository name

A short name for a repository (called Alias within Zypper and Repository Name within YaST). It can be chosen by the user when adding a repository and must be unique.

Repository description files

Each repository provides files describing content of the repository (package names, versions, etc.). These repository description files are downloaded to a local cache that is used by YaST.

Product

Represents a whole product, for example SUSE® Linux Enterprise Server.

Pattern

A pattern is an installable group of packages dedicated to a certain purpose. For example, the Laptop pattern contains all packages that are needed in a mobile computing environment. Patterns define package dependencies (such as required or recommended packages) and come with a preselection of packages marked for installation. This ensures that the most important packages needed for a certain purpose are available on your system after installation of the pattern. If necessary, you can manually select or deselect packages within a pattern.

Package

A package is a compressed file in rpm format that contains the files for a particular program.

Patch

A patch consists of one or more packages and may be applied by delta RPMs. It may also introduce dependencies to packages that are not installed yet.

Resolvable

A generic term for product, pattern, package or patch. The most commonly used type of resolvable is a package or a patch.

Delta RPM

A delta RPM consists only of the binary diff between two defined versions of a package, and therefore has the smallest download size. Before being installed, the full RPM package is rebuilt on the local machine.

Package dependencies

Certain packages are dependent on other packages, such as shared libraries. In other terms, a package may require other packages—if the required packages are not available, the package cannot be installed. In addition to dependencies (package requirements) that must be fulfilled, certain packages recommend other packages. These recommended packages are only installed if they are actually available, otherwise they are ignored and the package recommending them is installed nevertheless.

8.2 Registering an installed system

If you skip registration during installation, or you want to re-register your system, you can register the system at any time. Use the YaST module Product Registration or the command line tool SUSEConnect.

8.2.1 Registering with YaST

To register the system, start YaST and switch to Software, then Product Registration.

By default the system is registered with the SUSE Customer Center. If your organization provides local registration servers, you can either choose one from the list of auto-detected servers or provide the URL manually.

8.2.2 Registering with SUSEConnect

To register from the command line, use the command

> sudo SUSEConnect -r REGISTRATION_CODE -e EMAIL_ADDRESS

Replace REGISTRATION_CODE with the registration code you received with your copy of SUSE Linux Enterprise Server. Replace EMAIL_ADDRESS with the e-mail address associated with the SUSE account you or your organization uses to manage subscriptions.

To register with a local registration server, also provide the URL to the server:

> sudo SUSEConnect -r REGISTRATION_CODE -e EMAIL_ADDRESS --url "URL"

8.3 Using the YaST software manager

Start the software manager from the YaST Control Center by choosing Software › Software Management.

YaST software manager screen

8.3.2 Installing and removing packages or patterns

Certain packages are dependent on other packages, such as shared libraries. Several packages cannot coexist with others on the system. If possible, YaST automatically resolves these dependencies or conflicts. If your choice results in a dependency conflict that cannot be automatically solved, you need to solve it manually as described in Section 8.3.4, “Package dependencies”.

Note
Note: Removal of packages

When removing any packages, by default YaST only removes the selected packages. If you want YaST to also remove any other packages that become unneeded after removal of the specified package, select Options › Cleanup when deleting packages from the main menu.

  1. Search for packages as described in Section 8.3.1, “Searching software”.

  2. The packages found are listed in the right pane. To install a package or remove it, right-click it and choose Install or Delete. If the relevant option is not available, check the package status indicated by the symbol in front of the package name—press ShiftF1 for help.

    Tip
    Tip: Applying an action to all packages listed

    To apply an action to all packages listed in the right pane, go to the main menu and choose an action from Package › All in This List.

  3. To install a pattern, right-click the pattern name and choose Install.

  4. It is not possible to remove a pattern. Instead, select the packages for the pattern you want to remove and mark them for removal.

  5. To select more packages, repeat the steps mentioned above.

  6. Before applying your changes, you can review or modify them by clicking View › Installation Summary. By default, all packages that will change status are listed.

  7. To revert the status for a package, right-click the package and select one of the following entries: Keep if the package was scheduled to be deleted or updated, or Do Not Install if it was scheduled for installation. To abandon all changes and quit the Software Manager, click Cancel and Abandon.

  8. When you are finished, click Accept to apply your changes.

  9. If YaST finds additional dependencies, it shows a list of related packages to install, update or remove. Click Continue to accept them.

    After all selected packages are installed, updated or removed, the YaST Software Manager automatically closes.

Note
Note: Installing source packages

Installing source packages with YaST Software Manager is not possible at the moment. Use the command line tool zypper for this purpose. For more information, see Section 9.1.3.5, “Installing or downloading source packages”.

8.3.3 Updating packages

Instead of updating individual packages, you can also update all installed packages or all packages from a certain repository. When mass updating packages, the following aspects are generally considered:

  • priorities of the repositories that provide the package,

  • architecture of the package (for example, AMD64/Intel 64),

  • version number of the package,

  • package vendor.

Which of the aspects has the highest importance for choosing the update candidates depends on the respective update option you choose.

  1. To update all installed packages to the latest version, choose Package › All Packages › Update if Newer Version Available from the main menu.

    All repositories are checked for possible update candidates, using the following policy: YaST first tries to restrict the search to packages with the same architecture and vendor as the installed one. If the search is positive, the best update candidate from those is selected according to the process below. However, if no comparable package of the same vendor can be found, the search is expanded to all packages with the same architecture. If still no comparable package can be found, all packages are considered and the best update candidate is selected according to the following criteria:

    1. Repository priority: prefer the package from the repository with the highest priority.

    2. If more than one package results from this selection, choose the one with the best architecture (best choice: matching the architecture of the installed one).

    If the resulting package has a higher version number than the installed one, the installed package will be updated and replaced with the selected update candidate.

    This option tries to avoid changes in architecture and vendor for the installed packages, but under certain circumstances, they are tolerated.

    Note
    Note: Update unconditionally

    If you choose Package › All Packages › Update Unconditionally instead, the same criteria apply but any candidate package found is installed unconditionally. Thus, choosing this option may lead to downgrading certain packages.

  2. To make sure that the packages for a mass update derive from a certain repository:

    1. Choose the repository from which to update as described in Section 8.3.1, “Searching software” .

    2. On the right hand side of the window, click Switch system packages to the versions in this repository. This explicitly allows YaST to change the package vendor when replacing the packages.

      When you proceed with Accept, all installed packages are replaced by packages deriving from this repository, if available. This may lead to changes in vendor and architecture and even to downgrading certain packages.

    3. To refrain from this, click Cancel switching system packages to the versions in this repository. You can only cancel this until you click the Accept button.

  3. Before applying your changes, you can review or modify them by clicking View › Installation Summary. By default, all packages that will change status, are listed.

  4. If all options are set according to your wishes, confirm your changes with Accept to start the mass update.

8.3.4 Package dependencies

Most packages are dependent on other packages. If a package, for example, uses a shared library, it is dependent on the package providing this library. Some packages cannot coexist, causing a conflict (for example, you can only install one mail transfer agent: sendmail or postfix). When installing or removing software, the Software Manager makes sure no dependencies or conflicts remain unsolved to ensure system integrity.

In case there exists only one solution to resolve a dependency or a conflict, it is resolved automatically. Multiple solutions always cause a conflict which needs to be resolved manually. If solving a conflict involves a vendor or architecture change, it also needs to be solved manually. When clicking Accept to apply any changes in the Software Manager, you get an overview of all actions triggered by the automatic resolver which you need to confirm.

By default, dependencies are automatically checked. A check is performed every time you change a package status (for example, by marking a package for installation or removal). This is generally useful, but can become exhausting when manually resolving a dependency conflict. To disable this function, go to the main menu and deactivate Dependencies › Autocheck. Manually perform a dependency check with Dependencies › Check Now. A consistency check is always performed when you confirm your selection with Accept.

To review a package's dependencies, right-click it and choose Show Solver Information. A map showing the dependencies opens. Packages that are already installed are displayed in a green frame.

Note
Note: Manually solving package conflicts

Unless you are experienced, follow the suggestions YaST makes when handling package conflicts, otherwise you may not be able to resolve them. Keep in mind that every change you make potentially triggers other conflicts, so you can easily end up with a steadily increasing number of conflicts. In case this happens, Cancel the Software Manager, Abandon all your changes and start again.

Conflict management of the software manager
Figure 8.1: Conflict management of the software manager

8.3.5 Handling package recommendations

In addition to the hard dependencies required to run a program (for example a certain library), a package can also have weak dependencies, which add for example extra functionality or translations. These weak dependencies are called package recommendations.

When installing a new package, recommended packages are still installed by default. When updating an existing package, missing recommendations are not be installed automatically. To change this, set PKGMGR_RECOMMENDED="yes" in /etc/sysconfig/yast2. To install all missing recommendations for already installed packages, start YaST › Software Manager and choose Extras › Install All Matching Recommended Packages.

To disable the installation of recommended packages when installing new packages, deactivate Dependencies › Install Recommended Packages in the YaST Software Manager. When using the command-line tool Zypper to install packages, use the option --no-recommends.

8.4 Managing software repositories and services

To install third-party software, add software repositories to your system. By default, product repositories such as SUSE Linux Enterprise Server-DVD 15 SP5 and a matching update repository are automatically configured when you register your system. For more information about registration, see Book “Deployment Guide”, Chapter 8 “Installation steps”, Section 8.7 “Registration” or Book “Upgrade Guide”, Chapter 4 “Upgrading offline”, Section 4.8 “Registering your system”. Depending on the initially selected product, an additional repository containing translations, dictionaries, etc. might also be configured.

To manage repositories, start YaST and select Software › Software Repositories. The Configured Software Repositories dialog opens. Here, you can also manage subscriptions to Services by changing the View at the right corner of the dialog to All Services. A Service in this context is a Repository Index Service (RIS) that can offer one or more software repositories. Such a Service can be changed dynamically by its administrator or vendor.

Each repository provides files describing repository content (package names, versions, etc.). YaST downloads these repository description files to a local cache. To ensure their integrity, software repositories can be signed with the GPG Key of the repository maintainer. Whenever you add a new repository, YaST offers the ability to import its key.

Warning
Warning: Trusting external software sources

Before adding external software repositories to your list of repositories, make sure this repository can be trusted. SUSE is not responsible for any problems arising from software installed from third-party software repositories.

8.4.1 Adding software repositories

You can either add repositories from DVD/CD, a USB flash drive, a local directory, an ISO image, or a network source.

To add repositories from the Configured Software Repositories dialog in YaST proceed as follows:

  1. Click Add.

  2. Select one of the options listed in the dialog:

    Adding a software repository
    Figure 8.2: Adding a software repository
    • To scan your network for installation servers announcing their services via SLP, select Scan Using SLP and click Next.

    • To add a repository from a removable medium, choose the relevant option and insert the medium or connect the USB device to the machine, respectively. Click Next to start the installation.

    • For the majority of repositories, you will be asked to specify the path (or URL) to the media after selecting the respective option and clicking Next. Specifying a Repository Name is optional. If none is specified, YaST will use the product name or the URL as repository name.

    The option Download Repository Description Files is activated by default. If you deactivate the option, YaST will automatically download the files later, if needed.

  3. Depending on the repository you add, you may be prompted to import the repository's GPG key or asked to agree to a license.

    After confirming, YaST will download and parse the metadata. It will add the repository to the list of Configured Repositories.

  4. If needed, adjust the repository Properties as described in Section 8.4.2, “Managing repository properties”.

  5. Confirm your changes with OK to close the configuration dialog.

  6. After having successfully added the repository, the software manager starts and you can install packages from this repository. For details, refer to Chapter 8, Installing or removing software.

8.4.2 Managing repository properties

The Configured Software Repositories overview of the Software Repositories lets you change the following repository properties:

Status

The repository status can either be Enabled or Disabled. You can only install packages from repositories that are enabled. To turn a repository off temporarily, select it and deactivate Enable. You can also double-click a repository name to toggle its status. To remove a repository completely, click Delete.

Refresh

When refreshing a repository, its content description (package names, versions, etc.) is downloaded to a local cache that is used by YaST. It is sufficient to do this once for static repositories such as CDs or DVDs, whereas repositories whose content changes often should be refreshed frequently. The easiest way to keep a repository's cache up to date is to choose Automatically Refresh. To do a manual refresh click Refresh and select one of the options.

Keep Downloaded Packages

Packages from remote repositories are downloaded before being installed. By default, they are deleted upon successful installation. Activating Keep Downloaded Packages prevents the deletion of downloaded packages. The download location is configured in /etc/zypp/zypp.conf, by default it is /var/cache/zypp/packages.

Priority

The Priority of a repository is a value between 1 and 200, with 1 being the highest priority and 200 the lowest priority. Any new repositories that are added with YaST get a priority of 99 by default. If you do not care about a priority value for a certain repository, you can also set the value to 0 to apply the default priority to that repository (99). If a package is available in more than one repository, then the repository with the highest priority takes precedence. This is useful to avoid downloading packages unnecessarily from the Internet by giving a local repository (for example, a DVD) a higher priority.

Important
Important: Priority compared to version

The repository with the highest priority takes precedence in any case. Therefore, make sure that the update repository always has the highest priority, otherwise you might install an outdated version that will not be updated until the next online update.

Name and URL

To change a repository name or its URL, select it from the list with a single-click and then click Edit.

8.4.3 Managing repository keys

To ensure their integrity, software repositories can be signed with the GPG Key of the repository maintainer. Whenever you add a new repository, YaST offers to import its key. Verify it as you would do with any other GPG key and make sure it does not change. If you detect a key change, something might be wrong with the repository. Disable the repository as an installation source until you know the cause of the key change.

To manage all imported keys, click GPG Keys in the Configured Software Repositories dialog. Select an entry with the mouse to show the key properties at the bottom of the window. Add, Edit, or Delete keys with a click on the respective buttons.

8.5 The GNOME package updater

SUSE offers a continuous stream of software security patches and updates for your product. They can be installed using tools available with your desktop or by running the YaST online update module. This section describes how to update the system from the GNOME desktop using the Package Updater.

Contrary to the YaST Online Update module, the GNOME Package Updater not only offers to install patches from the update repositories, but also new versions of packages that are already installed. (Patches fix security issues or malfunctions; the functionality and version number is usually not changed. New versions of a package increase the version number and usually add functionality or introduce major changes.)

Whenever new patches or package updates are available, GNOME shows a notification in the notification area or on the lock screen.

Update notification on GNOME desktop
Figure 8.3: Update notification on GNOME desktop

To configure the notification settings for the Package Updater, start GNOME Settings and choose Notifications › Package Updater.

Procedure 8.2: Installing patches and updates with the GNOME package updater
  1. To install the patches and updates, click the notification message. This opens the GNOME Package Updater. Alternatively, open the updater from Activities by typing package U and choosing Package Updater.

    Image
  2. Updates are sorted into four categories:

    Security updates (patches)

    Fix severe security hazards and should always be installed.

    Recommended updates (patches)

    Fix issues that could compromise your computer. Installing them is strongly recommended.

    Optional updates (patches)

    Fix non-security relevant issues or provide enhancements.

    Other updates

    New versions of packages that are installed.

    All available updates are preselected for installation. If you do not want to install all updates, deselect unwanted updates first. It is strongly recommended to always install all security and recommended updates.

    To get detailed information on an update, click its title and then Details. The information will be displayed in a box beneath the package list.

  3. Click Install Updates to start the installation.

  4. Some updates may require to restart the machine or to log out. Check the message displayed after installation for instructions.

8.6 Updating packages with GNOME Software

In addition to the GNOME Package Updater, GNOME provides GNOME Software which has the following functionality:

  • Install, update, and remove software delivered as an RPM via PackageKit

  • Install, update, and remove software delivered as a Flatpak

  • Install, update, and remove GNOME shell extensions (https://extensions.gnome.org)

  • Update firmware for hardware devices using Linux Vendor Firmware Service (LVFS, https://fwupd.org)

In addition to this, GNOME Software provides screenshots, ratings, and reviews for software.

GNOME Software—Updates view
Figure 8.4: GNOME SoftwareUpdates view

GNOME Software has the following differences to other tools provided on SUSE Linux Enterprise Server:

  • Unlike YaST or Zypper, for installing software packaged as an RPM, GNOME Software is restricted to software that provides AppStream metadata. This includes most desktop applications.

  • While the GNOME Package Updater updates packages within the running system (forcing you to restart the respective applications), GNOME Software downloads the updates and applies them after reboot.

9 Managing software with command line tools

This chapter describes Zypper and RPM, two command line tools for managing software. For a definition of the terminology used in this context (for example, repository, patch, or update) refer to Section 8.1, “Definition of terms”.

9.1 Using Zypper

Zypper is a command line package manager for installing, updating, and removing packages. It also manages repositories. It is especially useful for accomplishing remote software management tasks or managing software from shell scripts.

9.1.1 General usage

The general syntax of Zypper is:

zypper [--global-options] COMMAND  [--command-options] [arguments]

The components enclosed in brackets are not required. See zypper help for a list of general options and all commands. To get help for a specific command, type zypper help COMMAND.

Zypper commands

The simplest way to execute Zypper is to type its name, followed by a command. For example, to apply all needed patches to the system, use:

> sudo zypper patch
Global options

Additionally, you can choose from one or more global options by typing them immediately before the command:

> sudo zypper --non-interactive patch

In the above example, the option --non-interactive means that the command is run without asking anything (automatically applying the default answers).

Command-specific options

To use options that are specific to a particular command, type them immediately after the command:

> sudo zypper patch --auto-agree-with-licenses

In the above example, --auto-agree-with-licenses is used to apply all needed patches to a system without you being asked to confirm any licenses. Instead, licenses will be accepted automatically.

Arguments

Some commands require one or more arguments. For example, when using the command install, you need to specify which package or which packages you want to install:

> sudo zypper install mplayer

Some options also require a single argument. The following command will list all known patterns:

> zypper search -t pattern

You can combine all of the above. For example, the following command will install the mc and vim packages from the factory repository while being verbose:

> sudo zypper -v install --from factory mc vim

The --from option keeps all repositories enabled (for solving any dependencies) while requesting the package from the specified repository. --repo is an alias for --from, and you may use either one.

Most Zypper commands have a dry-run option that does a simulation of the given command. It can be used for test purposes.

> sudo zypper remove --dry-run MozillaFirefox

Zypper supports the global --userdata STRING option. You can specify a string with this option, which gets written to Zypper's log files and plug-ins (such as the Btrfs plug-in). It can be used to mark and identify transactions in log files.

> sudo zypper --userdata STRING patch

9.1.2 Using Zypper subcommands

Zypper subcommands are executables that are stored in the directory specified by the zypper_execdir configuration option. It is /usr/lib/zypper/commands by default. If a subcommand is not found there, Zypper automatically searches the rest of your $PATH locations for it. This lets you create your own local extensions and store them in user space.

Executing subcommands in the Zypper shell, and using global Zypper options are not supported.

List your available subcommands:

> zypper help subcommand
[...]
Available zypper subcommands in '/usr/lib/zypper/commands'

  appstream-cache
  lifecycle
  migration
  search-packages

Zypper subcommands available from elsewhere on your $PATH

  log                   Zypper logfile reader
                            (/usr/sbin/zypper-log)

View the help screen for a subcommand:

> zypper help appstream-cache

9.1.3 Installing and removing software with Zypper

To install or remove packages, use the following commands:

> sudo zypper install PACKAGE_NAME
> sudo zypper remove PACKAGE_NAME
Warning
Warning: Do not remove mandatory system packages

Do not remove mandatory system packages like glibc , zypper , kernel . If they are removed, the system can become unstable or stop working altogether.

9.1.3.1 Selecting which packages to install or remove

There are various ways to address packages with the commands zypper install and zypper remove.

By exact package name
> sudo zypper install MozillaFirefox
By exact package name and version number
> sudo zypper install MozillaFirefox-52.2
By repository alias and package name
> sudo zypper install mozilla:MozillaFirefox

Where mozilla is the alias of the repository from which to install.

By package name using wild cards

You can select all packages that have names starting or ending with a certain string. Use wild cards with care, especially when removing packages. The following command will install all packages starting with Moz:

> sudo zypper install 'Moz*'
Tip
Tip: Removing all -debuginfo packages

When debugging a problem, you sometimes need to temporarily install a lot of -debuginfo packages which give you more information about running processes. After your debugging session finishes and you need to clean the environment, run the following:

> sudo zypper remove '*-debuginfo'
By capability

For example, to install a package without knowing its name, capabilities come in handy. The following command will install the package MozillaFirefox:

> sudo zypper install firefox
By capability, hardware architecture, or version

Together with a capability, you can specify a hardware architecture and a version:

  • The name of the desired hardware architecture is appended to the capability after a full stop. For example, to specify the AMD64/Intel 64 architectures (which in Zypper is named x86_64), use:

    > sudo zypper install 'firefox.x86_64'
  • Versions must be appended to the end of the string and must be preceded by an operator: < (lesser than), <= (lesser than or equal), = (equal), >= (greater than or equal), > (greater than).

    > sudo zypper install 'firefox>=74.2'
  • You can also combine a hardware architecture and version requirement:

    > sudo zypper install 'firefox.x86_64>=74.2'
By path to the RPM file

You can also specify a local or remote path to a package:

> sudo zypper install /tmp/install/MozillaFirefox.rpm
> sudo zypper install http://download.example.com/MozillaFirefox.rpm

9.1.3.2 Combining installation and removal of packages

To install and remove packages simultaneously, use the +/- modifiers. To install emacs and simultaneously remove vim , use:

> sudo zypper install emacs -vim

To remove emacs and simultaneously install vim , use:

> sudo zypper remove emacs +vim

To prevent the package name starting with the - being interpreted as a command option, always use it as the second argument. If this is not possible, precede it with --:

> sudo zypper install -emacs +vim       # Wrong
> sudo zypper install vim -emacs        # Correct
> sudo zypper install -- -emacs +vim    # Correct
> sudo zypper remove emacs +vim         # Correct

9.1.3.3 Cleaning up dependencies of removed packages

If (together with a certain package), you automatically want to remove any packages that become unneeded after removing the specified package, use the --clean-deps option:

> sudo zypper rm --clean-deps PACKAGE_NAME

9.1.3.4 Using Zypper in scripts

By default, Zypper asks for a confirmation before installing or removing a selected package, or when a problem occurs. You can override this behavior using the --non-interactive option. This option must be given before the actual command (install, remove, and patch), as can be seen in the following:

> sudo zypper --non-interactive install PACKAGE_NAME

This option allows the use of Zypper in scripts and cron jobs.

9.1.3.5 Installing or downloading source packages

To install the corresponding source package of a package, use:

> zypper source-install PACKAGE_NAME

When executed as root, the default location to install source packages is /usr/src/packages/ and ~/rpmbuild when run as user. These values can be changed in your local rpm configuration.

This command will also install the build dependencies of the specified package. If you do not want this, add the switch -D:

> sudo zypper source-install -D PACKAGE_NAME

To install only the build dependencies use -d.

> sudo zypper source-install -d PACKAGE_NAME

Of course, this will only work if you have the repository with the source packages enabled in your repository list (it is added by default, but not enabled). See Section 9.1.6, “Managing repositories with Zypper” for details on repository management.

A list of all source packages available in your repositories can be obtained with:

> zypper search -t srcpackage

You can also download source packages for all installed packages to a local directory. To download source packages, use:

> zypper source-download

The default download directory is /var/cache/zypper/source-download. You can change it using the --directory option. To only show missing or extraneous packages without downloading or deleting anything, use the --status option. To delete extraneous source packages, use the --delete option. To disable deleting, use the --no-delete option.

9.1.3.6 Installing packages from disabled repositories

Normally you can only install or refresh packages from enabled repositories. The --plus-content TAG option helps you specify repositories to be refreshed, temporarily enabled during the current Zypper session, and disabled after it completes.

For example, to enable repositories that may provide additional -debuginfo or -debugsource packages, use --plus-content debug. You can specify this option multiple times.

To temporarily enable such 'debug' repositories to install a specific -debuginfo package, use the option as follows:

> sudo zypper --plus-content debug \
   install "debuginfo(build-id)=eb844a5c20c70a59fc693cd1061f851fb7d046f4"

The build-id string is reported by gdb for missing debuginfo packages.

Note
Note: Disabled installation media

Repositories from the SUSE Linux Enterprise Server installation media are still configured but disabled after successful installation. You can use the --plus-content option to install packages from the installation media instead of the online repositories. Before calling zypper, ensure the media is available, for example by inserting the DVD into the computer's drive.

9.1.3.7 Utilities

To verify whether all dependencies are still fulfilled and to repair missing dependencies, use:

> zypper verify

In addition to dependencies that must be fulfilled, some packages recommend other packages. These recommended packages are only installed if actually available and installable. In case recommended packages were made available after the recommending package has been installed (by adding additional packages or hardware), use the following command:

> sudo zypper install-new-recommends

This command is very useful after plugging in a Web cam or Wi-Fi device. It will install drivers for the device and related software, if available. Drivers and related software are only installable if certain hardware dependencies are fulfilled.

9.1.4 Updating software with Zypper

There are three different ways to update software using Zypper: by installing patches, by installing a new version of a package or by updating the entire distribution. The latter is achieved with zypper dist-upgrade. Upgrading SUSE Linux Enterprise Server is discussed in Book “Upgrade Guide”, Chapter 2 “Upgrade paths and methods”.

9.1.4.1 Installing all needed patches

Patching SUSE Linux Enterprise Server is the most reliable way to install new versions of installed packages. It guarantees that all required packages with correct versions are installed and ensures that package versions considered as conflicting are omitted.

To install all officially released patches that apply to your system, run:

> sudo zypper patch

All patches available from repositories configured on your computer are checked for their relevance to your installation. If they are relevant (and not classified as optional or feature), they are installed immediately. If zypper patch succeeds, it is guaranteed that no vulnerable version package is installed unless you confirm the exception. Note that the official update repository is only available after registering your SUSE Linux Enterprise Server installation.

If a patch that is about to be installed includes changes that require a system reboot, you will be warned before.

The plain zypper patch command does not apply patches from third party repositories. To update also the third party repositories, use the with-update command option as follows:

> sudo zypper patch --with-update

To install also optional patches, use:

> sudo zypper patch --with-optional

To install all patches relating to a specific Bugzilla issue, use:

> sudo zypper patch --bugzilla=NUMBER

To install all patches relating to a specific CVE database entry, use:

> sudo zypper patch --cve=NUMBER

For example, to install a security patch with the CVE number CVE-2010-2713, execute:

> sudo zypper patch --cve=CVE-2010-2713

To install only patches which affect Zypper and the package management itself, use:

> sudo zypper patch --updatestack-only

Bear in mind that other command options that would also update other repositories will be dropped if you use the updatestack-only command option.

9.1.4.2 Listing patches

To find out whether patches are available, Zypper allows viewing the following information:

Number of needed patches

To list the number of needed patches (patches that apply to your system but are not yet installed), use patch-check:

> zypper patch-check
Loading repository data...
Reading installed packages...
5 patches needed (1 security patch)

This command can be combined with the --updatestack-only option to list only the patches which affect Zypper and the package management itself.

List of needed patches

To list all needed patches (patches that apply to your system but are not yet installed), use zypper list-patches.

List of all patches

To list all patches available for SUSE Linux Enterprise Server, regardless of whether they are already installed or apply to your installation, use zypper patches.

It is also possible to list and install patches relevant to specific issues. To list specific patches, use the zypper list-patches command with the following options:

By Bugzilla issues

To list all needed patches that relate to Bugzilla issues, use the option --bugzilla.

To list patches for a specific bug, you can also specify a bug number: --bugzilla=NUMBER. To search for patches relating to multiple Bugzilla issues, add commas between the bug numbers, for example:

> zypper list-patches --bugzilla=972197,956917
By CVE number

To list all needed patches that relate to an entry in the CVE database (Common Vulnerabilities and Exposures), use the option --cve.

To list patches for a specific CVE database entry, you can also specify a CVE number: --cve=NUMBER. To search for patches relating to multiple CVE database entries, add commas between the CVE numbers, for example:

> zypper list-patches --cve=CVE-2016-2315,CVE-2016-2324
List retracted patches

In the SUSE Linux Enterprise 15 codestream, some patches are automatically retracted. Maintenance updates are carefully tested, because there is a risk that an update contains a new bug. If an update proves to contain a bug, a new update (with a higher version number) is issued to revert the buggy update, and the buggy update is blocked from being installed again. You can list retracted patches with zypper:

> zypper lp --all |grep retracted
SLE-Module-Basesystem15-SP3-Updates | SUSE-SLE-Module-Basesystem-15-SP3-2021-1965
 | recommended | important | ---    | retracted  | Recommended update for multipath-tools
SLE-Module-Basesystem15-SP3-Updates | SUSE-SLE-Module-Basesystem-15-SP3-2021-2689
 | security    | important | ---    | retracted  | Security update for cpio
SLE-Module-Basesystem15-SP3-Updates | SUSE-SLE-Module-Basesystem-15-SP3-2021-3655
 | security    | important | reboot | retracted  | Security update for the Linux Kernel

See complete information on a retracted (or any) patch:

> zypper patch-info SUSE-SLE-Product-SLES-15-2021-2689
Loading repository data...
Reading installed packages...

Information for patch SUSE-SLE-Product-SLES-15-2021-2689:
---------------------------------------------------------
Repository  : SLE-Product-SLES15-LTSS-Updates
Name        : SUSE-SLE-Product-SLES-15-2021-2689
Version     : 1
Arch        : noarch
Vendor      : maint-coord@suse.de
Status      : retracted
Category    : security
Severity    : important
Created On  : Mon 16 Aug 2021 03:44:00 AM PDT
Interactive : ---
Summary     : Security update for cpio
Description :
    This update for cpio fixes the following issues:

    It was possible to trigger Remote code execution due to a integer overflow
    (CVE-2021-38185, bsc#1189206)

    UPDATE:
    This update was buggy and could lead to hangs, so it has been retracted.
    There will be a follow up update.
    [...]
Patch with conflicting packages
Information for patch openSUSE-SLE-15.3-2022-333:
-------------------------------------------------
Repository  : Update repository with updates from SUSE Linux Enterprise 15
Name        : openSUSE-SLE-15.3-2022-333
Version     : 1
Arch        : noarch
Vendor      : maint-coord@suse.de
Status      : needed
Category    : security
Severity    : important
Created On  : Fri Feb  4 09:30:32 2022
Interactive : reboot
Summary     : Security update for xen
Description :
    This update for xen fixes the following issues:

    - CVE-2022-23033: Fixed guest_physmap_remove_page not removing the p2m mappings. (XSA-393) (bsc#1194576)
    - CVE-2022-23034: Fixed possible DoS by a PV guest Xen while unmapping a grant. (XSA-394) (bsc#1194581)
    - CVE-2022-23035: Fixed insufficient cleanup of passed-through device IRQs. (XSA-395) (bsc#1194588)
Provides    : patch:openSUSE-SLE-15.3-2022-333 = 1
Conflicts   : [22]
    xen.src < 4.14.3_06-150300.3.18.2
    xen.noarch < 4.14.3_06-150300.3.18.2
    xen.x86_64 < 4.14.3_06-150300.3.18.2
    xen-devel.x86_64 < 4.14.3_06-150300.3.18.2
    xen-devel.noarch < 4.14.3_06-150300.3.18.2
[...]

The above patch conflicts with the affected or vulnerable versions of 22 packages. If any of these affected or vulnerable packages are installed, it triggers a conflict, and the patch is classified as needed. zypper patch tries to install all available patches. If it encounters problems, it reports them, thus informing you that not all updates are installed. The conflict can be resolved by either updating the affected or vulnerable packages or by removing them. Because SUSE update repositories also ship fixed packages, updating is a standard way to resolve conflicts. If the package cannot be updated—for example, because of dependency issues or package locks—it is deleted after the user's approval.

To list all patches regardless of whether they are needed, use the option --all additionally. For example, to list all patches with a CVE number assigned, use:

> zypper list-patches --all --cve
Issue | No.           | Patch             | Category    | Severity  | Status
------+---------------+-------------------+-------------+-----------+----------
cve   | CVE-2019-0287 | SUSE-SLE-Module.. | recommended | moderate  | needed
cve   | CVE-2019-3566 | SUSE-SLE-SERVER.. | recommended | moderate  | not needed
[...]

9.1.4.3 Installing new package versions

If a repository contains only new packages, but does not provide patches, zypper patch does not show any effect. To update all installed packages with newer available versions, use the following command:

> sudo zypper update
Important
Important

zypper update ignores problematic packages. For example, if a package is locked, zypper update omits the package, even if a higher version of it is available. Conversely, zypper patch reports a conflict if the package is considered vulnerable.

To update individual packages, specify the package with either the update or install command:

> sudo zypper update PACKAGE_NAME
> sudo zypper install PACKAGE_NAME

A list of all new installable packages can be obtained with the command:

> zypper list-updates

Note that this command only lists packages that match the following criteria:

  • has the same vendor like the already installed package,

  • is provided by repositories with at least the same priority than the already installed package,

  • is installable (all dependencies are satisfied).

A list of all new available packages (regardless whether installable or not) can be obtained with:

> sudo zypper list-updates --all

To find out why a new package cannot be installed, use the zypper install or zypper update command as described above.

9.1.4.4 Identifying orphaned packages

Whenever you remove a repository from Zypper or upgrade your system, some packages can get in an orphaned state. These orphaned packages belong to no active repository anymore. The following command gives you a list of these:

> sudo zypper packages --orphaned

With this list, you can decide if a package is still needed or can be removed safely.

9.1.5 Identifying processes and services using deleted files

When patching, updating, or removing packages, there may be running processes on the system which continue to use files having been deleted by the update or removal. Use zypper ps to list processes using deleted files. In case the process belongs to a known service, the service name is listed, making it easy to restart the service. By default zypper ps shows a table:

> zypper ps
PID   | PPID | UID | User  | Command      | Service      | Files
------+------+-----+-------+--------------+--------------+-------------------
814   | 1    | 481 | avahi | avahi-daemon | avahi-daemon | /lib64/ld-2.19.s->
      |      |     |       |              |              | /lib64/libdl-2.1->
      |      |     |       |              |              | /lib64/libpthrea->
      |      |     |       |              |              | /lib64/libc-2.19->
[...]
PID: ID of the process
PPID: ID of the parent process
UID: ID of the user running the process
Login: Login name of the user running the process
Command: Command used to execute the process
Service: Service name (only if command is associated with a system service)
Files: The list of the deleted files

The output format of zypper ps can be controlled as follows:

zypper ps-s

Create a short table not showing the deleted files.

> zypper ps -s
PID   | PPID | UID  | User    | Command      | Service
------+------+------+---------+--------------+--------------
814   | 1    | 481  | avahi   | avahi-daemon | avahi-daemon
817   | 1    | 0    | root    | irqbalance   | irqbalance
1567  | 1    | 0    | root    | sshd         | sshd
1761  | 1    | 0    | root    | master       | postfix
1764  | 1761 | 51   | postfix | pickup       | postfix
1765  | 1761 | 51   | postfix | qmgr         | postfix
2031  | 2027 | 1000 | tux     | bash         |
zypper ps-ss

Show only processes associated with a system service.

PID   | PPID | UID  | User    | Command      | Service
------+------+------+---------+--------------+--------------
814   | 1    | 481  | avahi   | avahi-daemon | avahi-daemon
817   | 1    | 0    | root    | irqbalance   | irqbalance
1567  | 1    | 0    | root    | sshd         | sshd
1761  | 1    | 0    | root    | master       | postfix
1764  | 1761 | 51   | postfix | pickup       | postfix
1765  | 1761 | 51   | postfix | qmgr         | postfix
zypper ps-sss

Only show system services using deleted files.

avahi-daemon
irqbalance
postfix
sshd
zypper ps--print "systemctl status %s"

Show the commands to retrieve status information for services which might need a restart.

systemctl status avahi-daemon
systemctl status irqbalance
systemctl status postfix
systemctl status sshd

For more information about service handling refer to Chapter 19, The systemd daemon.

9.1.6 Managing repositories with Zypper

All installation or patch commands of Zypper rely on a list of known repositories. To list all repositories known to the system, use the command:

> zypper repos

The result will look similar to the following output:

Example 9.1: Zypper—list of known repositories
> zypper repos
# | Alias        | Name          | Enabled | Refresh
--+--------------+---------------+---------+--------
1 | SLEHA-15-GEO | SLEHA-15-GEO  | Yes     | No
2 | SLEHA-15     | SLEHA-15      | Yes     | No
3 | SLES15       | SLES15        | Yes     | No

When specifying repositories in various commands, an alias, URI or repository number from the zypper repos command output can be used. A repository alias is a short version of the repository name for use in repository handling commands. Note that the repository numbers can change after modifying the list of repositories. The alias will never change by itself.

By default, details such as the URI or the priority of the repository are not displayed. Use the following command to list all details:

> zypper repos -d

9.1.6.1 Adding repositories

To add a repository, run

> sudo zypper addrepo URI ALIAS

URI can either be an Internet repository, a network resource, a directory or a CD or DVD (see https://en.opensuse.org/openSUSE:Libzypp_URIs for details). The ALIAS is a shorthand and unique identifier of the repository. You can freely choose it, with the only exception that it needs to be unique. Zypper will issue a warning if you specify an alias that is already in use.

9.1.6.2 Refreshing repositories

zypper enables you to fetch changes in packages from configured repositories. To fetch the changes, run:

> sudo zypper refresh
Note
Note: Default behavior of zypper

By default, some commands perform refresh automatically, so you do not need to run the command explicitly.

The refresh command enables you to view changes also in disabled repositories, by using the --plus-content option:

> sudo zypper --plus-content refresh

This option fetches changes in repositories, but keeps the disabled repositories in the same state—disabled.

9.1.6.3 Removing repositories

To remove a repository from the list, use the command zypper removerepo together with the alias or number of the repository you want to delete. For example, to remove the repository SLEHA-12-GEO from Example 9.1, “Zypper—list of known repositories”, use one of the following commands:

> sudo zypper removerepo 1
> sudo zypper removerepo "SLEHA-12-GEO"

9.1.6.4 Modifying repositories

Enable or disable repositories with zypper modifyrepo. You can also alter the repository's properties (such as refreshing behavior, name or priority) with this command. The following command will enable the repository named updates, turn on auto-refresh and set its priority to 20:

> sudo zypper modifyrepo -er -p 20 'updates'

Modifying repositories is not limited to a single repository—you can also operate on groups:

-a: all repositories
-l: local repositories
-t: remote repositories
-m TYPE: repositories of a certain type (where TYPE can be one of the following: http, https, ftp, cd, dvd, dir, file, cifs, smb, nfs, hd, iso)

To rename a repository alias, use the renamerepo command. The following example changes the alias from Mozilla Firefox to firefox:

> sudo zypper renamerepo 'Mozilla Firefox' firefox

9.1.7 Querying repositories and packages with Zypper

Zypper offers various methods to query repositories or packages. To get lists of all products, patterns, packages or patches available, use the following commands:

> zypper products
> zypper patterns
> zypper packages
> zypper patches

To query all repositories for certain packages, use search. To get information regarding particular packages, use the info command.

9.1.7.2 Searching for packages across all SLE modules

To search for packages both within and outside of currently enabled SLE modules, use the search-packages subcommand. This command contacts the SUSE Customer Center and searches all modules for matching packages, for example:

> zypper search-packages package1 package2

zypper search-packages provides the following options:

  • Search for an exact match of your search string: -x, --match-exact

  • Group the results by module (default: group by package): -g, --group-by-module

  • Display more detailed information about packages: -d, --details

  • Output search results in XML: --xmlout

9.1.7.3 Searching for specific capability

To search for packages which provide a special capability, use the command what-provides. For example, if you want to know which package provides the Perl module SVN::Core, use the following command:

> zypper what-provides 'perl(SVN::Core)'

The what-provides PACKAGE_NAME is similar to rpm -q --whatprovides PACKAGE_NAME, but RPM is only able to query the RPM database (that is the database of all installed packages). Zypper, on the other hand, will tell you about providers of the capability from any repository, not only those that are installed.

9.1.7.4 Showing package information

To query single packages, use info with an exact package name as an argument. This displays detailed information about a package. In case the package name does not match any package name from repositories, the command outputs detailed information for non-package matches. If you request a specific type (by using the -t option) and the type does not exist, the command outputs other available matches but without detailed information.

If you specify a source package, the command displays binary packages built from the source package. If you specify a binary package, the command outputs the source packages used to build the binary package.

To also show what is required/recommended by the package, use the options --requires and --recommends:

> zypper info --requires MozillaFirefox

9.1.8 Showing lifecycle information

SUSE products are generally supported for 10 years. Often, you can extend that standard lifecycle by using the extended support offerings of SUSE which add three years of support. Depending on your product, find the exact support lifecycle at https://www.suse.com/lifecycle.

To check the lifecycle of your product and the supported package, use the zypper lifecycle command as shown below:

# zypper lifecycle
    Product end of support
Codestream: SUSE Linux Enterprise Server 15             2028-07-31
    Product: SUSE Linux Enterprise Server 15 SP3        n/a*

Module end of support
Basesystem Module                                       n/a*
Desktop Applications Module                             n/a*
Server Applications Module                              n/a*

Package end of support if different from product:
autofs                                   Now, installed 5.1.3-7.3.1, update available 5.1.3-7.6.1

9.1.9 Configuring Zypper

Zypper now comes with a configuration file, allowing you to permanently change Zypper's behavior (either system-wide or user-specific). For system-wide changes, edit /etc/zypp/zypper.conf. For user-specific changes, edit ~/.zypper.conf. If ~/.zypper.conf does not yet exist, you can use /etc/zypp/zypper.conf as a template: copy it to ~/.zypper.conf and adjust it to your liking. Refer to the comments in the file for help about the available options.

9.1.10 Troubleshooting

If you have trouble accessing packages from configured repositories (for example, Zypper cannot find a certain package even though you know it exists in one of the repositories), refreshing the repositories may help:

> sudo zypper refresh

If that does not help, try

> sudo zypper refresh -fdb

This forces a complete refresh and rebuild of the database, including a forced download of raw metadata.

9.1.11 Zypper rollback feature on Btrfs file system

If the Btrfs file system is used on the root partition and snapper is installed, Zypper automatically calls snapper when committing changes to the file system to create appropriate file system snapshots. These snapshots can be used to revert any changes made by Zypper. See Chapter 10, System recovery and snapshot management with Snapper for more information.

9.1.12 More information

For more information on managing software from the command line, enter zypper help, zypper help  COMMAND or refer to the zypper(8) man page. For a complete and detailed command reference, cheat sheets with the most important commands, and information on how to use Zypper in scripts and applications, refer to https://en.opensuse.org/SDB:Zypper_usage. A list of software changes for the latest SUSE Linux Enterprise Server version can be found at https://en.opensuse.org/openSUSE:Zypper_versions.

9.2 RPM—the package manager

RPM (RPM Package Manager) is used for managing software packages. Its main commands are rpm and rpmbuild. The powerful RPM database can be queried by the users, system administrators and package builders for detailed information about the installed software.

rpm has five modes: installing, uninstalling (or updating) software packages, rebuilding the RPM database, querying RPM bases or individual RPM archives, integrity checking of packages and signing packages. rpmbuild can be used to build installable packages from pristine sources.

Installable RPM archives are packed in a special binary format. These archives consist of the program files to install and certain meta information used during the installation by rpm to configure the software package or stored in the RPM database for documentation purposes. RPM archives normally have the extension .rpm.

Tip
Tip: Software development packages

For several packages, the components needed for software development (libraries, headers, include files, etc.) have been put into separate packages. These development packages are only needed if you want to compile software yourself (for example, the most recent GNOME packages). They can be identified by the name extension -devel, such as the packages alsa-devel and gimp-devel.

9.2.1 Verifying package authenticity

RPM packages have a GPG signature. To verify the signature of an RPM package, use the command rpm --checksig  PACKAGE-1.2.3.rpm to determine whether the package originates from SUSE or from another trustworthy facility. This is especially recommended for update packages from the Internet.

While fixing issues in the operating system, you might need to install a Problem Temporary Fix (PTF) into a production system. The packages provided by SUSE are signed against a special PTF key. However, in contrast to SUSE Linux Enterprise 11, this key is not imported by default on SUSE Linux Enterprise 12 systems. To manually import the key, use the following command:

> sudo rpm --import \
/usr/share/doc/packages/suse-build-key/suse_ptf_key.asc

After importing the key, you can install PTF packages on your system.

9.2.2 Managing packages: install, update, and uninstall

Normally, the installation of an RPM archive is quite simple: rpm -i PACKAGE.rpm. With this command the package is installed, but only if its dependencies are fulfilled and if there are no conflicts with other packages. With an error message, rpm requests those packages that need to be installed to meet dependency requirements. In the background, the RPM database ensures that no conflicts arise—a specific file can only belong to one package. By choosing different options, you can force rpm to ignore these defaults, but this is only for experts. Otherwise, you risk compromising the integrity of the system and possibly jeopardize the ability to update the system.

The options -U or --upgrade and -F or --freshen can be used to update a package (for example, rpm -F PACKAGE.rpm). This command removes the files of the old version and immediately installs the new files. The difference between the two versions is that -U installs packages that previously did not exist in the system, while -F merely updates previously installed packages. When updating, rpm updates configuration files carefully using the following strategy:

  • If a configuration file was not changed by the system administrator, rpm installs the new version of the appropriate file. No action by the system administrator is required.

  • If a configuration file was changed by the system administrator before the update, rpm saves the changed file with the extension .rpmorig or .rpmsave (backup file) and installs the version from the new package. This is done only if the originally installed file and the newer version are different. If this is the case, compare the backup file (.rpmorig or .rpmsave) with the newly installed file and make your changes again in the new file. Afterward, delete all .rpmorig and .rpmsave files to avoid problems with future updates.

  • .rpmnew files appear if the configuration file already exists and if the noreplace label was specified in the .spec file.

Following an update, .rpmsave and .rpmnew files should be removed after comparing them, so they do not obstruct future updates. The .rpmorig extension is assigned if the file has not previously been recognized by the RPM database.

Otherwise, .rpmsave is used. In other words, .rpmorig results from updating from a foreign format to RPM. .rpmsave results from updating from an older RPM to a newer RPM. .rpmnew does not disclose any information to whether the system administrator has made any changes to the configuration file. A list of these files is available in /var/adm/rpmconfigcheck. Some configuration files (like /etc/httpd/httpd.conf) are not overwritten to allow continued operation.

The -U switch is not only an equivalent to uninstalling with the -e option and installing with the -i option. Use -U whenever possible.

To remove a package, enter rpm -e PACKAGE. This command only deletes the package if there are no unresolved dependencies. It is theoretically impossible to delete Tcl/Tk, for example, as long as another application requires it. Even in this case, RPM calls for assistance from the database. If such a deletion is, for whatever reason, impossible (even if no additional dependencies exist), it may be helpful to rebuild the RPM database using the option --rebuilddb.

9.2.3 Delta RPM packages

Delta RPM packages contain the difference between an old and a new version of an RPM package. Applying a delta RPM onto an old RPM results in a completely new RPM. It is not necessary to have a copy of the old RPM because a delta RPM can also work with an installed RPM. The delta RPM packages are even smaller in size than patch RPMs, which is an advantage when transferring update packages over the Internet. The drawback is that update operations with delta RPMs involved consume considerably more CPU cycles than plain or patch RPMs.

The makedeltarpm and applydelta binaries are part of the delta RPM suite (package deltarpm) and help you create and apply delta RPM packages. With the following commands, you can create a delta RPM called new.delta.rpm. The following command assumes that old.rpm and new.rpm are present:

> sudo makedeltarpm old.rpm new.rpm new.delta.rpm

Using applydeltarpm, you can reconstruct the new RPM from the file system if the old package is already installed:

> sudo applydeltarpm new.delta.rpm new.rpm

To derive it from the old RPM without accessing the file system, use the -r option:

> sudo applydeltarpm -r old.rpm new.delta.rpm new.rpm

See /usr/share/doc/packages/deltarpm/README for technical details.

9.2.4 RPM queries

With the -q option rpm initiates queries, making it possible to inspect an RPM archive (by adding the option -p) and to query the RPM database of installed packages. Several switches are available to specify the type of information required. See Table 9.1, “Essential RPM query options”.

Table 9.1: Essential RPM query options

-i

Package information

-l

File list

-f FILE

Query the package that contains the file FILE (the full path must be specified with FILE)

-s

File list with status information (implies -l)

-d

List only documentation files (implies -l)

-c

List only configuration files (implies -l)

--dump

File list with complete details (to be used with -l, -c, or -d)

--provides

List features of the package that another package can request with --requires

--requires, -R

Capabilities the package requires

--scripts

Installation scripts (preinstall, postinstall, uninstall)

For example, the command rpm -q -i wget displays the information shown in Example 9.2, “rpm -q -i wget.

Example 9.2: rpm -q -i wget
Name        : wget
Version     : 1.14
Release     : 17.1
Architecture: x86_64
Install Date: Mon 30 Jan 2017 14:01:29 CET
Group       : Productivity/Networking/Web/Utilities
Size        : 2046483
License     : GPL-3.0+
Signature   : RSA/SHA256, Thu 08 Dec 2016 07:48:44 CET, Key ID 70af9e8139db7c82
Source RPM  : wget-1.14-17.1.src.rpm
Build Date  : Thu 08 Dec 2016 07:48:34 CET
Build Host  : sheep09
Relocations : (not relocatable)
Packager    : https://www.suse.com/
Vendor      : SUSE LLC <https://www.suse.com/>
URL         : http://www.gnu.org/software/wget/
Summary     : A Tool for Mirroring FTP and HTTP Servers
Description :
Wget enables you to retrieve WWW documents or FTP files from a server.
This can be done in script files or via the command line.
Distribution: SUSE Linux Enterprise 15

The option -f only works if you specify the complete file name with its full path. Provide as many file names as desired. For example:

> rpm -q -f /bin/rpm /usr/bin/wget
rpm-4.14.1-lp151.13.10.x86_64
wget-1.19.5-lp151.4.1.x86_64

If only part of the file name is known, use a shell script as shown in Example 9.3, “Script to search for packages”. Pass the partial file name to the script shown as a parameter when running it.

The command rpm -q --changelog PACKAGE displays a detailed list of change information about a specific package, sorted by date.

With the installed RPM database, verification checks can be made. Initiate these with -V, or --verify. With this option, rpm shows all files in a package that have been changed since installation. rpm uses eight character symbols to give some hints about the following changes:

Table 9.2: RPM verify options

5

MD5 check sum

S

File size

L

Symbolic link

T

Modification time

D

Major and minor device numbers

U

Owner

G

Group

M

Mode (permissions and file type)

In the case of configuration files, the letter c is printed. For example, for changes to /etc/wgetrc (wget package):

> rpm -V wget
S.5....T c /etc/wgetrc

The files of the RPM database are placed in /var/lib/rpm. If the partition /usr has a size of 1 GB, this database can occupy nearly 30 MB, especially after a complete update. If the database is much larger than expected, it is useful to rebuild the database with the option --rebuilddb. Before doing this, make a backup of the old database. The cron script cron.daily makes daily copies of the database (packed with gzip) and stores them in /var/adm/backup/rpmdb. The number of copies is controlled by the variable MAX_RPMDB_BACKUPS (default: 5) in /etc/sysconfig/backup. The size of a single backup is approximately 1 MB for 1 GB in /usr.

9.2.5 Installing and compiling source packages

All source packages carry a .src.rpm extension (source RPM).

Note
Note: Installed source packages

Source packages can be copied from the installation medium to the hard disk and unpacked with YaST. They are not, however, marked as installed ([i]) in the package manager. This is because the source packages are not entered in the RPM database. Only installed operating system software is listed in the RPM database. When you install a source package, only the source code is added to the system.

The following directories must be available for rpm and rpmbuild in /usr/src/packages (unless you specified custom settings in a file like /etc/rpmrc):

SOURCES

for the original sources (.tar.bz2 or .tar.gz files, etc.) and for distribution-specific adjustments (mostly .diff or .patch files)

SPECS

for the .spec files, similar to a meta Makefile, which control the build process

BUILD

all the sources are unpacked, patched and compiled in this directory

RPMS

where the completed binary packages are stored

SRPMS

here are the source RPMs

When you install a source package with YaST, all the necessary components are installed in /usr/src/packages: the sources and the adjustments in SOURCES and the relevant .spec file in SPECS.

Warning
Warning: System integrity

Do not experiment with system components (glibc, rpm, etc.), because this endangers the stability of your system.

The following example uses the wget.src.rpm package. After installing the source package, you should have files similar to those in the following list:

/usr/src/packages/SOURCES/wget-1.19.5.tar.bz2
/usr/src/packages/SOURCES/wgetrc.patch
/usr/src/packages/SPECS/wget.spec

rpmbuild -bX /usr/src/packages/SPECS/wget.spec starts the compilation. X is a wild card for various stages of the build process (see the output of --help or the RPM documentation for details). The following is merely a brief explanation:

-bp

Prepare sources in /usr/src/packages/BUILD: unpack and patch.

-bc

Do the same as -bp, but with additional compilation.

-bi

Do the same as -bp, but with additional installation of the built software. Caution: if the package does not support the BuildRoot feature, you might overwrite configuration files.

-bb

Do the same as -bi, but with the additional creation of the binary package. If the compile was successful, the binary should be in /usr/src/packages/RPMS.

-ba

Do the same as -bb, but with the additional creation of the source RPM. If the compilation was successful, the binary should be in /usr/src/packages/SRPMS.

--short-circuit

Skip some steps.

The binary RPM created can now be installed with rpm -i or, preferably, with rpm -U. Installation with rpm makes it appear in the RPM database.

Keep in mind that the BuildRoot directive in the spec file is deprecated. If you still need this feature, use the --buildroot option as a workaround.

9.2.6 Compiling RPM packages with build

The danger with many packages is that unwanted files are added to the running system during the build process. To prevent this use build, which creates a defined environment in which the package is built. To establish this chroot environment, the build script must be provided with a complete package tree. This tree can be made available on the hard disk, via NFS, or from DVD. Set the position with build --rpms DIRECTORY. Unlike rpm, the build command looks for the .spec file in the source directory. To build wget (like in the above example) with the DVD mounted in the system under /media/dvd, use the following commands as root:

# cd /usr/src/packages/SOURCES/
# mv ../SPECS/wget.spec .
# build --rpms /media/dvd/suse/ wget.spec

Subsequently, a minimum environment is established at /var/tmp/build-root. The package is built in this environment. Upon completion, the resulting packages are located in /var/tmp/build-root/usr/src/packages/RPMS.

The build script offers several additional options. For example, cause the script to prefer your own RPMs, omit the initialization of the build environment or limit the rpm command to one of the above-mentioned stages. Access additional information with build --help and by reading the build man page.

9.2.7 Tools for RPM archives and the RPM database

Midnight Commander (mc) can display the contents of RPM archives and copy parts of them. It represents archives as virtual file systems, offering all usual menu options of Midnight Commander. Display the HEADER with F3. View the archive structure with the cursor keys and Enter. Copy archive components with F5.

A full-featured package manager is available as a YaST module. For details, see Chapter 8, Installing or removing software.

10 System recovery and snapshot management with Snapper

Snapper allows creating and managing file system snapshots. File system snapshots allow keeping a copy of the state of a file system at a certain point of time. The standard setup of Snapper is designed to allow rolling back system changes. However, you can also use it to create on-disk backups of user data. As the basis for this functionality, Snapper uses the Btrfs file system or thinly-provisioned LVM volumes with an XFS or Ext4 file system.

Snapper has a command line interface and a YaST interface. Snapper lets you create and manage file system snapshots on the following types of file systems:

  • Btrfs, a copy-on-write file system for Linux that natively supports file system snapshots of subvolumes. (Subvolumes are separately mountable file systems within a physical partition.)

    You can also boot from Btrfs snapshots. For more information, see Section 10.3, “System rollback by booting from snapshots”.

  • Thinly-provisioned LVM volumes formatted with XFS or Ext4.

Using Snapper, you can perform the following tasks:

10.1 Default setup

Snapper on SUSE Linux Enterprise Server is set up as an undo and recovery tool for system changes. By default, the root partition (/) of SUSE Linux Enterprise Server is formatted with Btrfs. Taking snapshots is automatically enabled if the root partition (/) is big enough (more than approximately 16 GB). By default, snapshots are disabled on partitions other than /.

Tip
Tip: Enabling Snapper in the installed system

If you disabled Snapper during the installation, you can enable it at any time later. To do so, create a default Snapper configuration for the root file system by running:

> sudo snapper -c root create-config /

Afterward enable the different snapshot types as described in Section 10.1.4.1, “Disabling/enabling snapshots”.

Note that on a Btrfs root file system, snapshots require a file system with subvolumes configured as proposed by the installer and a partition size of at least 16 GB.

When a snapshot is created, both the snapshot and the original point to the same blocks in the file system. So, initially a snapshot does not occupy additional disk space. If data in the original file system is modified, changed data blocks are copied while the old data blocks are kept for the snapshot. Therefore, a snapshot occupies the same amount of space as the data modified. So, over time, the amount of space a snapshot allocates, constantly grows. As a consequence, deleting files from a Btrfs file system containing snapshots may not free disk space!

Note
Note: Snapshot location

Snapshots always reside on the same partition or subvolume on which the snapshot has been taken. It is not possible to store snapshots on a different partition or subvolume.

As a result, partitions containing snapshots need to be larger than partitions not containing snapshots. The exact amount depends strongly on the number of snapshots you keep and the amount of data modifications. As a rule of thumb, give partitions twice as much space as you normally would. To prevent disks from running out of space, old snapshots are automatically cleaned up. Refer to Section 10.1.4.4, “Controlling snapshot archiving” for details.

10.1.1 Default settings

Disks larger than 16 GB
  • Configuration file: /etc/snapper/configs/root

  • USE_SNAPPER=yes

  • TIMELINE_CREATE=no

Disks smaller than 16 GB
  • Configuration file: not created

  • USE_SNAPPER=no

  • TIMELINE_CREATE=yes

10.1.2 Types of snapshots

Although snapshots themselves do not differ in a technical sense, we distinguish between three types of snapshots, based on the events that trigger them:

Timeline snapshots

A single snapshot is created every hour. Old snapshots are automatically deleted. By default, the first snapshot of the last ten days, months, and years are kept. Using the YaST OS installation method (default), timeline snapshots are enabled, except for the root file system.

Installation snapshots

Whenever one or more packages are installed with YaST or Zypper, a pair of snapshots is created: one before the installation starts (Pre) and another one after the installation has finished (Post). In case an important system component such as the kernel has been installed, the snapshot pair is marked as important (important=yes). Old snapshots are automatically deleted. By default the last ten important snapshots and the last ten regular (including administration snapshots) snapshots are kept. Installation snapshots are enabled by default.

Administration snapshots

Whenever you administrate the system with YaST, a pair of snapshots is created: one when a YaST module is started (Pre) and another when the module is closed (Post). Old snapshots are automatically deleted. By default the last ten important snapshots and the last ten regular snapshots (including installation snapshots) are kept. Administration snapshots are enabled by default.

10.1.3 Directories that are excluded from snapshots

Some directories need to be excluded from snapshots for different reasons. The following list shows all directories that are excluded:

/boot/grub2/i386-pc, /boot/grub2/x86_64-efi, /boot/grub2/powerpc-ieee1275, /boot/grub2/s390x-emu

A rollback of the boot loader configuration is not supported. The directories listed above are architecture-specific. The first two directories are present on AMD64/Intel 64 machines, the latter two on IBM POWER and on IBM Z, respectively.

/home

If /home does not reside on a separate partition, it is excluded to avoid data loss on rollbacks.

/opt

Third-party products usually get installed to /opt. It is excluded to avoid uninstalling these applications on rollbacks.

/srv

Contains data for Web and FTP servers. It is excluded to avoid data loss on rollbacks.

/tmp

All directories containing temporary files and caches are excluded from snapshots.

/usr/local

This directory is used when manually installing software. It is excluded to avoid uninstalling these installations on rollbacks.

/var

This directory contains many variable files, including logs, temporary caches, third party products in /var/opt, and is the default location for virtual machine images and databases. Therefore this subvolume is created to exclude all of this variable data from snapshots and has Copy-On-Write disabled.

10.1.4 Customizing the setup

SUSE Linux Enterprise Server comes with a reasonable default setup, which should be sufficient for most use cases. However, all aspects of taking automatic snapshots and snapshot keeping can be configured according to your needs.

10.1.4.1 Disabling/enabling snapshots

Each of the three snapshot types (timeline, installation, administration) can be enabled or disabled independently.

Disabling/enabling timeline snapshots

Enabling.  snapper -c root set-config "TIMELINE_CREATE=yes"

Disabling.  snapper -c root set-config "TIMELINE_CREATE=no"

Using the YaST OS installation method (default), timeline snapshots are enabled, except for the root file system.

Disabling/enabling installation snapshots

Enabling: Install the package snapper-zypp-plugin

Disabling: Uninstall the package snapper-zypp-plugin

Installation snapshots are enabled by default.

Disabling/enabling administration snapshots

Enabling: Set USE_SNAPPER to yes in /etc/sysconfig/yast2.

Disabling: Set USE_SNAPPER to no in /etc/sysconfig/yast2.

Administration snapshots are enabled by default.

10.1.4.2 Controlling installation snapshots

Taking snapshot pairs upon installing packages with YaST or Zypper is handled by the snapper-zypp-plugin. An XML configuration file, /etc/snapper/zypp-plugin.conf defines, when to make snapshots. By default the file looks like the following:

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <snapper-zypp-plugin-conf>
 3  <solvables>
 4   <solvable match="w"1 important="true"2>kernel-*3</solvable>
 5   <solvable match="w" important="true">dracut</solvable>
 6   <solvable match="w" important="true">glibc</solvable>
 7   <solvable match="w" important="true">systemd*</solvable>
 8   <solvable match="w" important="true">udev</solvable>
 9   <solvable match="w">*</solvable>4
10  </solvables>
11 </snapper-zypp-plugin-conf>

1

The match attribute defines whether the pattern is a Unix shell-style wild card (w) or a Python regular expression (re).

2

If the given pattern matches and the corresponding package is marked as important (for example kernel packages), the snapshot will also be marked as important.

3

Pattern to match a package name. Based on the setting of the match attribute, special characters are either interpreted as shell wild cards or regular expressions. This pattern matches all package names starting with kernel-.

4

This line unconditionally matches all packages.

With this configuration snapshot, pairs are made whenever a package is installed (line 9). When the kernel, dracut, glibc, systemd, or udev packages marked as important are installed, the snapshot pair will also be marked as important (lines 4 to 8). All rules are evaluated.

To disable a rule, either delete it or deactivate it using XML comments. To prevent the system from making snapshot pairs for every package installation for example, comment line 9:

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <snapper-zypp-plugin-conf>
 3  <solvables>
 4   <solvable match="w" important="true">kernel-*</solvable>
 5   <solvable match="w" important="true">dracut</solvable>
 6   <solvable match="w" important="true">glibc</solvable>
 7   <solvable match="w" important="true">systemd*</solvable>
 8   <solvable match="w" important="true">udev</solvable>
 9   <!-- <solvable match="w">*</solvable> -->
10  </solvables>
11 </snapper-zypp-plugin-conf>

10.1.4.3 Creating and mounting new subvolumes

Creating a new subvolume underneath the / hierarchy and permanently mounting it is supported. Such a subvolume will be excluded from snapshots. You need to make sure not to create it inside an existing snapshot, since you would not be able to delete snapshots anymore after a rollback.

SUSE Linux Enterprise Server is configured with the /@/ subvolume which serves as an independent root for permanent subvolumes such as /opt, /srv, /home and others. Any new subvolumes you create and permanently mount need to be created in this initial root file system.

To do so, run the following commands. In this example, a new subvolume /usr/important is created from /dev/sda2.

> sudo mount /dev/sda2 -o subvol=@ /mnt
> sudo btrfs subvolume create /mnt/usr/important
> sudo umount /mnt

The corresponding entry in /etc/fstab needs to look like the following:

/dev/sda2 /usr/important btrfs subvol=@/usr/important 0 0
Tip
Tip: Disable copy-on-write (cow)

A subvolume may contain files that constantly change, such as virtualized disk images, database files, or log files. If so, consider disabling the copy-on-write feature for this volume, to avoid duplication of disk blocks. Use the nodatacow mount option in /etc/fstab to do so:

/dev/sda2 /usr/important btrfs nodatacow,subvol=@/usr/important 0 0

To alternatively disable copy-on-write for single files or directories, use the command chattr +C PATH.

10.1.4.4 Controlling snapshot archiving

Snapshots occupy disk space. To prevent disks from running out of space and thus causing system outages, old snapshots are automatically deleted. By default, up to ten important installation and administration snapshots and up to ten regular installation and administration snapshots are kept. If these snapshots occupy more than 50% of the root file system size, additional snapshots will be deleted. A minimum of four important and two regular snapshots are always kept.

Refer to Section 10.5.1, “Managing existing configurations” for instructions on how to change these values.

10.1.4.5 Using Snapper on thinly provisioned LVM volumes

Apart from snapshots on Btrfs file systems, Snapper also supports taking snapshots on thinly-provisioned LVM volumes (snapshots on regular LVM volumes are not supported) formatted with XFS, Ext4 or Ext3. For more information and setup instructions on LVM volumes, refer to Book “Deployment Guide”, Chapter 10 “Expert Partitioner”, Section 10.2 “LVM configuration”.

To use Snapper on a thinly-provisioned LVM volume you need to create a Snapper configuration for it. On LVM it is required to specify the file system with --fstype=lvm(FILESYSTEM). ext3, etx4 or xfs are valid values for FILESYSTEM. Example:

> sudo snapper -c lvm create-config --fstype="lvm(xfs)" /thin_lvm

You can adjust this configuration according to your needs as described in Section 10.5.1, “Managing existing configurations”.

10.2 Using Snapper to undo changes

Snapper on SUSE Linux Enterprise Server is preconfigured to serve as a tool that lets you undo changes made by zypper and YaST. For this purpose, Snapper is configured to create a pair of snapshots before and after each run of zypper and YaST. Snapper also lets you restore system files that have been accidentally deleted or modified. Timeline snapshots for the root partition need to be enabled for this purpose—see Section 10.1.4.1, “Disabling/enabling snapshots” for details.

By default, automatic snapshots as described above are configured for the root partition and its subvolumes. To make snapshots available for other partitions such as /home for example, you can create custom configurations.

Important
Important: Undoing changes compared to rollback

When working with snapshots to restore data, it is important to know that there are two fundamentally different scenarios Snapper can handle:

Undoing changes

When undoing changes as described in the following, two snapshots are being compared and the changes between these two snapshots are made undone. Using this method also allows to explicitly select the files that should be restored.

Rollback

When doing rollbacks as described in Section 10.3, “System rollback by booting from snapshots”, the system is reset to the state at which the snapshot was taken.

When undoing changes, it is also possible to compare a snapshot against the current system. When restoring all files from such a comparison, this will have the same result as doing a rollback. However, using the method described in Section 10.3, “System rollback by booting from snapshots” for rollbacks should be preferred, since it is faster and allows you to review the system before doing the rollback.

Warning
Warning: Data consistency

There is no mechanism to ensure data consistency when creating a snapshot. Whenever a file (for example, a database) is written at the same time as the snapshot is being created, it will result in a corrupted or partly written file. Restoring such a file will cause problems. Furthermore, certain system files such as /etc/mtab must never be restored. Therefore it is strongly recommended to always closely review the list of changed files and their diffs. Only restore files that really belong to the action you want to revert.

10.2.1 Undoing YaST and Zypper changes

If you set up the root partition with Btrfs during the installation, Snapper—preconfigured for doing rollbacks of YaST or Zypper changes—will automatically be installed. Every time you start a YaST module or a Zypper transaction, two snapshots are created: a pre-snapshot capturing the state of the file system before the start of the module and a post-snapshot after the module has been finished.

Using the YaST Snapper module or the snapper command line tool, you can undo the changes made by YaST/Zypper by restoring files from the pre-snapshot. Comparing two snapshots the tools also allow you to see which files have been changed. You can also display the differences between two versions of a file (diff).

Procedure 10.1: Undoing changes using the YaST Snapper module
  1. Start the Snapper module from the Miscellaneous section in YaST or by entering yast2 snapper.

  2. Make sure Current Configuration is set to root. This is always the case unless you have manually added own Snapper configurations.

  3. Choose a pair of pre- and post-snapshots from the list. Both, YaST and Zypper snapshot pairs are of the type Pre & Post. YaST snapshots are labeled as zypp(y2base) in the Description column; Zypper snapshots are labeled zypp(zypper).

    Image
  4. Click Show Changes to open the list of files that differ between the two snapshots.

    Image
  5. Review the list of files. To display a diff between the pre- and post-version of a file, select it from the list.

    Image
  6. To restore one or more files, select the relevant files or directories by activating the respective check box. Click Restore Selected and confirm the action by clicking Yes.

    Image

    To restore a single file, activate its diff view by clicking its name. Click Restore From First and confirm your choice with Yes.

Procedure 10.2: Undoing changes using the snapper command
  1. Get a list of YaST and Zypper snapshots by running snapper list -t pre-post. YaST snapshots are labeled as yast MODULE_NAME in the Description column; Zypper snapshots are labeled zypp(zypper).

    > sudo snapper list -t pre-post
    Pre # | Post # | Pre Date                      | Post Date                     | Description
    ------+--------+-------------------------------+-------------------------------+--------------
    311   | 312    | Tue 06 May 2018 14:05:46 CEST | Tue 06 May 2018 14:05:52 CEST | zypp(y2base)
    340   | 341    | Wed 07 May 2018 16:15:10 CEST | Wed 07 May 2018 16:15:16 CEST | zypp(zypper)
    342   | 343    | Wed 07 May 2018 16:20:38 CEST | Wed 07 May 2018 16:20:42 CEST | zypp(y2base)
    344   | 345    | Wed 07 May 2018 16:21:23 CEST | Wed 07 May 2018 16:21:24 CEST | zypp(zypper)
    346   | 347    | Wed 07 May 2018 16:41:06 CEST | Wed 07 May 2018 16:41:10 CEST | zypp(y2base)
    348   | 349    | Wed 07 May 2018 16:44:50 CEST | Wed 07 May 2018 16:44:53 CEST | zypp(y2base)
    350   | 351    | Wed 07 May 2018 16:46:27 CEST | Wed 07 May 2018 16:46:38 CEST | zypp(y2base)
  2. Get a list of changed files for a snapshot pair with snapper status PRE..POST. Files with content changes are marked with c, files that have been added are marked with + and deleted files are marked with -.

    > sudo snapper status 350..351
    +..... /usr/share/doc/packages/mikachan-fonts
    +..... /usr/share/doc/packages/mikachan-fonts/COPYING
    +..... /usr/share/doc/packages/mikachan-fonts/dl.html
    c..... /usr/share/fonts/truetype/fonts.dir
    c..... /usr/share/fonts/truetype/fonts.scale
    +..... /usr/share/fonts/truetype/みかちゃん-p.ttf
    +..... /usr/share/fonts/truetype/みかちゃん-pb.ttf
    +..... /usr/share/fonts/truetype/みかちゃん-ps.ttf
    +..... /usr/share/fonts/truetype/みかちゃん.ttf
    c..... /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86_64.cache-4
    c..... /var/lib/rpm/Basenames
    c..... /var/lib/rpm/Dirnames
    c..... /var/lib/rpm/Group
    c..... /var/lib/rpm/Installtid
    c..... /var/lib/rpm/Name
    c..... /var/lib/rpm/Packages
    c..... /var/lib/rpm/Providename
    c..... /var/lib/rpm/Requirename
    c..... /var/lib/rpm/Sha1header
    c..... /var/lib/rpm/Sigmd5
  3. To display the diff for a certain file, run snapper diff PRE..POST FILENAME. If you do not specify FILENAME, a diff for all files will be displayed.

    > sudo snapper diff 350..351 /usr/share/fonts/truetype/fonts.scale
    --- /.snapshots/350/snapshot/usr/share/fonts/truetype/fonts.scale       2014-04-23 15:58:57.000000000 +0200
    +++ /.snapshots/351/snapshot/usr/share/fonts/truetype/fonts.scale       2014-05-07 16:46:31.000000000 +0200
    @@ -1,4 +1,4 @@
    -1174
    +1486
     ds=y:ai=0.2:luximr.ttf -b&h-luxi mono-bold-i-normal--0-0-0-0-c-0-iso10646-1
     ds=y:ai=0.2:luximr.ttf -b&h-luxi mono-bold-i-normal--0-0-0-0-c-0-iso8859-1
    [...]
  4. To restore one or more files run snapper -v undochange PRE..POST FILENAMES. If you do not specify a FILENAMES, all changed files will be restored.

    > sudo snapper -v undochange 350..351
         create:0 modify:13 delete:7
         undoing change...
         deleting /usr/share/doc/packages/mikachan-fonts
         deleting /usr/share/doc/packages/mikachan-fonts/COPYING
         deleting /usr/share/doc/packages/mikachan-fonts/dl.html
         deleting /usr/share/fonts/truetype/みかちゃん-p.ttf
         deleting /usr/share/fonts/truetype/みかちゃん-pb.ttf
         deleting /usr/share/fonts/truetype/みかちゃん-ps.ttf
         deleting /usr/share/fonts/truetype/みかちゃん.ttf
         modifying /usr/share/fonts/truetype/fonts.dir
         modifying /usr/share/fonts/truetype/fonts.scale
         modifying /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86_64.cache-4
         modifying /var/lib/rpm/Basenames
         modifying /var/lib/rpm/Dirnames
         modifying /var/lib/rpm/Group
         modifying /var/lib/rpm/Installtid
         modifying /var/lib/rpm/Name
         modifying /var/lib/rpm/Packages
         modifying /var/lib/rpm/Providename
         modifying /var/lib/rpm/Requirename
         modifying /var/lib/rpm/Sha1header
         modifying /var/lib/rpm/Sigmd5
         undoing change done
Warning
Warning: Reverting user additions

Reverting user additions via undoing changes with Snapper is not recommended. Since certain directories are excluded from snapshots, files belonging to these users will remain in the file system. If a user with the same user ID as a deleted user is created, this user will inherit the files. Therefore it is strongly recommended to use the YaST User and Group Management tool to remove users.

10.2.2 Using Snapper to restore files

Apart from the installation and administration snapshots, Snapper creates timeline snapshots. You can use these backup snapshots to restore files that have accidentally been deleted or to restore a previous version of a file. By using Snapper's diff feature you can also find out which modifications have been made at a certain point of time.

Being able to restore files is especially interesting for data, which may reside on subvolumes or partitions for which snapshots are not taken by default. To be able to restore files from home directories, for example, create a separate Snapper configuration for /home doing automatic timeline snapshots. See Section 10.5, “Creating and modifying Snapper configurations” for instructions.

Warning
Warning: Restoring files compared to rollback

Snapshots taken from the root file system (defined by Snapper's root configuration), can be used to do a system rollback. The recommended way to do such a rollback is to boot from the snapshot and then perform the rollback. See Section 10.3, “System rollback by booting from snapshots” for details.

Performing a rollback would also be possible by restoring all files from a root file system snapshot as described below. However, this is not recommended. You may restore single files, for example a configuration file from the /etc directory, but not the complete list of files from the snapshot.

This restriction only affects snapshots taken from the root file system.

Procedure 10.3: Restoring files using the YaST Snapper module
  1. Start the Snapper module from the Miscellaneous section in YaST or by entering yast2 snapper.

  2. Choose the Current Configuration from which to choose a snapshot.

  3. Select a timeline snapshot from which to restore a file and choose Show Changes. Timeline snapshots are of the type Single with a description value of timeline.

  4. Select a file from the text box by clicking the file name. The difference between the snapshot version and the current system is shown. Activate the check box to select the file for restore. Do so for all files you want to restore.

  5. Click Restore Selected and confirm the action by clicking Yes.

Procedure 10.4: Restoring files using the snapper command
  1. Get a list of timeline snapshots for a specific configuration by running the following command:

    > sudo snapper -c CONFIG list -t single | grep timeline

    CONFIG needs to be replaced by an existing Snapper configuration. Use snapper list-configs to display a list.

  2. Get a list of changed files for a given snapshot by running the following command:

    > sudo snapper -c CONFIG status SNAPSHOT_ID..0

    Replace SNAPSHOT_ID by the ID for the snapshot from which you want to restore the files.

  3. Optionally list the differences between the current file version and the one from the snapshot by running

    > sudo snapper -c CONFIG diff SNAPSHOT_ID..0 FILE NAME

    If you do not specify <FILE NAME>, the difference for all files are shown.

  4. To restore one or more files, run

    > sudo snapper -c CONFIG -v undochange SNAPSHOT_ID..0 FILENAME1 FILENAME2

    If you do not specify file names, all changed files will be restored.

10.3 System rollback by booting from snapshots

The GRUB 2 version included on SUSE Linux Enterprise Server can boot from Btrfs snapshots. Together with Snapper's rollback feature, this allows to recover a misconfigured system. Only snapshots created for the default Snapper configuration (root) are bootable.

Important
Important: Supported configuration

As of SUSE Linux Enterprise Server 15 SP5 system rollbacks are only supported if the default subvolume configuration of the root partition has not been changed.

When booting a snapshot, the parts of the file system included in the snapshot are mounted read-only; all other file systems and parts that are excluded from snapshots are mounted read-write and can be modified.

Important
Important: Undoing changes compared to rollback

When working with snapshots to restore data, it is important to know that there are two fundamentally different scenarios Snapper can handle:

Undoing changes

When undoing changes as described in Section 10.2, “Using Snapper to undo changes”, two snapshots are compared and the changes between these two snapshots are reverted. Using this method also allows to explicitly exclude selected files from being restored.

Rollback

When doing rollbacks as described in the following, the system is reset to the state at which the snapshot was taken.

To do a rollback from a bootable snapshot, the following requirements must be met. When doing a default installation, the system is set up accordingly.

Requirements for a rollback from a bootable snapshot
  • The root file system needs to be Btrfs. Booting from LVM volume snapshots is not supported.

  • The root file system needs to be on a single device. To check, run sudo /sbin/btrfs filesystem show. It needs to report Total devices 1. If more than 1 device is listed, your setup is not supported.

    Note
    Note: Directories excluded from rollback

    Directories that are excluded from snapshots such as /srv (see Section 10.1.3, “Directories that are excluded from snapshots” for a full list) may reside on separate devices.

  • The system needs to be bootable via the installed boot loader.

  • Only contents of the subvolume / will be rolled back. It is not possible to include other subvolumes.

To perform a rollback from a bootable snapshot, do as follows:

  1. Boot the system. In the boot menu choose Bootable snapshots and select the snapshot you want to boot. The list of snapshots is listed by date—the most recent snapshot is listed first.

  2. Log in to the system. Carefully check whether everything works as expected. Note that you cannot write to any directory that is part of the snapshot. Data you write to other directories will not get lost, regardless of what you do next.

  3. Depending on whether you want to perform the rollback or not, choose your next step:

    1. If the system is in a state where you do not want to do a rollback, reboot to boot into the current system state. You can then choose a different snapshot, or start the rescue system.

    2. To perform the rollback, run

      > sudo snapper rollback

      and reboot afterward. On the boot screen, choose the default boot entry to reboot into the reinstated system. A snapshot of the file system status before the rollback is created. The default subvolume for root will be replaced with a fresh read-write snapshot. For details, see Section 10.3.1, “Snapshots after rollback”.

      It is useful to add a description for the snapshot with the -d option. For example:

      New file system root since rollback on DATE TIME
Tip
Tip: Rolling back to a specific installation state

If snapshots are not disabled during installation, an initial bootable snapshot is created at the end of the initial system installation. You can go back to that state at any time by booting this snapshot. The snapshot can be identified by the description after installation.

A bootable snapshot is also created when starting a system upgrade to a service pack or a new major release (provided snapshots are not disabled).

10.3.1 Snapshots after rollback

Before a rollback is performed, a snapshot of the running file system is created. The description references the ID of the snapshot that was restored in the rollback.

Snapshots created by rollbacks receive the value number for the Cleanup attribute. The rollback snapshots are therefore automatically deleted when the set number of snapshots is reached. Refer to Section 10.7, “Automatic snapshot clean-up” for details. If the snapshot contains important data, extract the data from the snapshot before it is removed.

10.3.1.1 Example of rollback snapshot

For example, after a fresh installation the following snapshots are available on the system:

# snapper --iso list
Type   | # |     | Cleanup | Description           | Userdata
-------+---+ ... +---------+-----------------------+--------------
single | 0 |     |         | current               |
single | 1 |     |         | first root filesystem |
single | 2 |     | number  | after installation    | important=yes

After running sudo snapper rollback snapshot 3 is created and contains the state of the system before the rollback was executed. Snapshot 4 is the new default Btrfs subvolume and thus the system after a reboot.

# snapper --iso list
Type   | # |     | Cleanup | Description           | Userdata
-------+---+ ... +---------+-----------------------+--------------
single | 0 |     |         | current               |
single | 1 |     | number  | first root filesystem |
single | 2 |     | number  | after installation    | important=yes
single | 3 |     | number  | rollback backup of #1 | important=yes
single | 4 |     |         |                       |

10.3.2 Accessing and identifying snapshot boot entries

To boot from a snapshot, reboot your machine and choose Start Bootloader from a read-only snapshot. A screen listing all bootable snapshots opens. The most recent snapshot is listed first, the oldest last. Use the keys and to navigate and press Enter to activate the selected snapshot. Activating a snapshot from the boot menu does not reboot the machine immediately, but rather opens the boot loader of the selected snapshot.

Boot loader: snapshots
Figure 10.1: Boot loader: snapshots
Warning
Warning: Booting Xen from a Btrfs snapshot using UEFI currently fails

Refer to https://www.suse.com/support/kb/doc/?id=000020602 for more details.

Each snapshot entry in the boot loader follows a naming scheme which makes it possible to identify it easily:

[*]1OS2 (KERNEL3,DATE4TTIME5,DESCRIPTION6)

1

If the snapshot was marked important, the entry is marked with a *.

2

Operating system label.

4

Date in the format YYYY-MM-DD.

5

Time in the format HH:MM.

6

This field contains a description of the snapshot. In case of a manually created snapshot this is the string created with the option --description or a custom string (see Tip: Setting a custom description for boot loader snapshot entries). In case of an automatically created snapshot, it is the tool that was called, for example zypp(zypper) or yast_sw_single. Long descriptions may be truncated, depending on the size of the boot screen.

Tip
Tip: Setting a custom description for boot loader snapshot entries

It is possible to replace the default string in the description field of a snapshot with a custom string. This is for example useful if an automatically created description is not sufficient, or a user-provided description is too long. To set a custom string STRING for snapshot NUMBER, use the following command:

> sudo snapper modify --userdata "bootloader=STRING" NUMBER

The description should be no longer than 25 characters—everything that exceeds this size will not be readable on the boot screen.

10.3.3 Limitations

A complete system rollback, restoring the complete system to the identical state as it was in when a snapshot was taken, is not possible.

10.3.3.1 Directories excluded from snapshots

Root file system snapshots do not contain all directories. See Section 10.1.3, “Directories that are excluded from snapshots” for details and reasons. As a general consequence, data from these directories is not restored, resulting in the following limitations.

Add-ons and third-party software may be unusable after a rollback

Applications and add-ons installing data in subvolumes excluded from the snapshot, such as /opt, may not work after a rollback, if others parts of the application data are also installed on subvolumes included in the snapshot. Re-install the application or the add-on to solve this problem.

File access problems

If an application had changed file permissions and/or ownership in between snapshot and current system, the application may not be able to access these files. Reset permissions and/or ownership for the affected files after the rollback.

Incompatible data formats

If a service or an application has established a new data format in between snapshot and current system, the application may not be able to read the affected data files after a rollback.

Subvolumes with a mixture of code and data

Subvolumes like /srv may contain a mixture of code and data. A rollback may result in non-functional code. A downgrade of the PHP version, for example, may result in broken PHP scripts for the Web server.

User data

If a rollback removes users from the system, data that is owned by these users in directories excluded from the snapshot, is not removed. If a user with the same user ID is created, this user will inherit the files. Use a tool like find to locate and remove orphaned files.

10.3.3.2 No rollback of boot loader data

A rollback of the boot loader is not possible, since all stages of the boot loader must fit together. This cannot be guaranteed when doing rollbacks of /boot.

10.4 Enabling Snapper in user home directories

You may enable snapshots for users' /home directories, which supports several use cases:

  • Individual users may manage their own snapshots and rollbacks.

  • System users, for example database, system, and network admins who want to track copies of configuration files, documentation, and so on.

  • Samba shares with home directories and Btrfs back-end.

Each user's directory is a Btrfs subvolume of /home. It is possible to set this up manually (see Section 10.4.3, “Manually enabling snapshots in home directories”). However, a more convenient way is to use pam_snapper. The pam_snapper package installs the pam_snapper.so module and helper scripts, which automate user creation and Snapper configuration.

pam_snapper provides integration with the useradd command, pluggable authentication modules (PAM), and Snapper. By default it creates snapshots at user login and logout, and also creates time-based snapshots as certain users remain logged in for extended periods of time. You may change the defaults using the normal Snapper commands and configuration files.

10.4.1 Installing pam_snapper and creating users

The easiest way is to start with a new /home directory formatted with Btrfs, and no existing users. Install pam_snapper:

# zypper in pam_snapper

Add this line to /etc/pam.d/common-session:

session optional pam_snapper.so

Use the /usr/lib/pam_snapper/pam_snapper_useradd.sh script to create a new user and home directory. By default the script performs a dry run. Edit the script to change DRYRUN=1 to DRYRUN=0. Now you can create a new user:

# /usr/lib/pam_snapper/pam_snapper_useradd.sh \
username group passwd=password
Create subvolume '/home/username'
useradd: warning: the home directory already exists.
Not copying any file from skel directory into it.

The files from /etc/skel will be copied into the user's home directory at their first login. Verify that the user's configuration was created by listing your Snapper configurations:

# snapper list --all
Config: home_username, subvolume: /home/username
Type   | # | Pre # | Date | User | Cleanup | Description | Userdata
-------+---+-------+------+------+---------+-------------+---------
single | 0 |       |      | root |         | current     |

Over time, this output will become populated with a list of snapshots, which the user can manage with the standard Snapper commands.

10.4.2 Removing users

Remove users with the /usr/lib/pam_snapper/pam_snapper_userdel.sh script. By default it performs a dry run, so edit it to change DRYRUN=1 to DRYRUN=0. This removes the user, the user's home subvolume, Snapper configuration, and deletes all snapshots.

# /usr/lib/pam_snapper/pam_snapper_userdel.sh username

10.4.3 Manually enabling snapshots in home directories

These are the steps for manually setting up users' home directories with Snapper. /home must be formatted with Btrfs, and the users not yet created.

# btrfs subvol create /home/username
# snapper -c home_username create-config /home/username
# sed -i -e "s/ALLOW_USERS=\"\"/ALLOW_USERS=\"username\"/g" \
/etc/snapper/configs/home_username
# yast users add username=username home=/home/username password=password
# chown username.group /home/username
# chmod 755 /home/username/.snapshots

10.5 Creating and modifying Snapper configurations

The way Snapper behaves is defined in a configuration file that is specific for each partition or Btrfs subvolume. These configuration files reside under /etc/snapper/configs/.

In case the root file system is big enough (approximately 12 GB), snapshots are automatically enabled for the root file system / upon installation. The corresponding default configuration is named root. It creates and manages the YaST and Zypper snapshot. See Section 10.5.1.1, “Configuration data” for a list of the default values.

Note
Note: Minimum root file system size for enabling snapshots

As explained in Section 10.1, “Default setup”, enabling snapshots requires additional free space in the root file system. The amount depends on the amount of packages installed and the amount of changes made to the volume that is included in snapshots. The snapshot frequency and the number of snapshots that get archived also matter.

There is a minimum root file system size that is required to automatically enable snapshots during the installation. Currently this size is approximately 12 GB. This value may change in the future, depending on architecture and the size of the base system. It depends on the values for the following tags in the file /control.xml from the installation media:

<root_base_size>
<btrfs_increase_percentage>

It is calculated with the following formula: ROOT_BASE_SIZE * (1 + BTRFS_INCREASE_PERCENTAGE/100)

Keep in mind that this value is a minimum size. Consider using more space for the root file system. As a rule of thumb, double the size you would use when not having enabled snapshots.

You may create your own configurations for other partitions formatted with Btrfs or existing subvolumes on a Btrfs partition. In the following example we will set up a Snapper configuration for backing up the Web server data residing on a separate, Btrfs-formatted partition mounted at /srv/www.

After a configuration has been created, you can either use snapper itself or the YaST Snapper module to restore files from these snapshots. In YaST you need to select your Current Configuration, while you need to specify your configuration for snapper with the global switch -c (for example, snapper -c myconfig list).

To create a new Snapper configuration, run snapper create-config:

> sudo snapper -c www-data1 create-config /srv/www2

1

Name of configuration file.

2

Mount point of the partition or Btrfs subvolume on which to take snapshots.

This command will create a new configuration file /etc/snapper/configs/www-data with reasonable default values (taken from /etc/snapper/config-templates/default). Refer to Section 10.5.1, “Managing existing configurations” for instructions on how to adjust these defaults.

Tip
Tip: Configuration defaults

Default values for a new configuration are taken from /etc/snapper/config-templates/default. To use your own set of defaults, create a copy of this file in the same directory and adjust it to your needs. To use it, specify the -t option with the create-config command:

> sudo snapper -c www-data create-config -t MY_DEFAULTS /srv/www

10.5.1 Managing existing configurations

The snapper command offers several subcommands for managing existing configurations. You can list, show, delete and modify them:

Listing configurations

Use the subcommand snapper list-configs to get all existing configurations:

> sudo snapper list-configs
Config | Subvolume
-------+----------
root   | /
usr    | /usr
local  | /local
Showing a configuration

Use the subcommand snapper -c CONFIG get-config to display the specified configuration. Replace CONFIG with one of the configuration names shown by snapper list-configs. For more information about the configuration options, see Section 10.5.1.1, “Configuration data”.

To display the default configuration, run:

> sudo snapper -c root get-config
Modifying a configuration

Use the subcommand snapper -c CONFIG set-config OPTION=VALUE to modify an option in the specified configuration. Replace CONFIG with one of the configuration names shown by snapper list-configs. Possible values for OPTION and VALUE are listed in Section 10.5.1.1, “Configuration data”.

Deleting a configuration

Use the subcommand snapper -c CONFIG delete-config to delete a configuration. Replace CONFIG with one of the configuration names shown by snapper list-configs.

10.5.1.1 Configuration data

Each configuration contains a list of options that can be modified from the command line. The following list provides details for each option. To change a value, run snapper -c CONFIG set-config "KEY=VALUE".

ALLOW_GROUPS, ALLOW_USERS

Granting permissions to use snapshots to regular users. See Section 10.5.1.2, “Using Snapper as regular user” for more information.

The default value is "".

BACKGROUND_COMPARISON

Defines whether pre and post snapshots should be compared in the background after creation.

The default value is "yes".

EMPTY_*

Defines the clean-up algorithm for snapshots pairs with identical pre and post snapshots. See Section 10.7.3, “Cleaning up snapshot pairs that do not differ” for details.

FSTYPE

File system type of the partition. Do not change.

The default value is "btrfs".

NUMBER_*

Defines the clean-up algorithm for installation and administration snapshots. See Section 10.7.1, “Cleaning up numbered snapshots” for details.

QGROUP / SPACE_LIMIT

Adds quota support to the clean-up algorithms. See Section 10.7.5, “Adding disk quota support” for details.

SUBVOLUME

Mount point of the partition or subvolume to snapshot. Do not change.

The default value is "/".

SYNC_ACL

If Snapper is used by regular users (see Section 10.5.1.2, “Using Snapper as regular user”), the users must be able to access the .snapshot directories and to read files within them. If SYNC_ACL is set to yes, Snapper automatically makes them accessible using ACLs for users and groups from the ALLOW_USERS or ALLOW_GROUPS entries.

The default value is "no".

TIMELINE_CREATE

If set to yes, hourly snapshots are created. Valid values: yes, no.

The default value is "no".

TIMELINE_CLEANUP / TIMELINE_LIMIT_*

Defines the clean-up algorithm for timeline snapshots. See Section 10.7.2, “Cleaning up timeline snapshots” for details.

10.5.1.2 Using Snapper as regular user

By default Snapper can only be used by root. However, there are cases in which certain groups or users need to be able to create snapshots or undo changes by reverting to a snapshot:

  • Web site administrators who want to take snapshots of /srv/www

  • Users who want to take a snapshot of their home directory

For these purposes, you can create Snapper configurations that grant permissions to users or/and groups. The corresponding .snapshots directory needs to be readable and accessible by the specified users. The easiest way to achieve this is to set the SYNC_ACL option to yes.

Procedure 10.5: Enabling regular users to use Snapper

All steps in this procedure need to be run by root.

  1. If a Snapper configuration does not exist yet, create one for the partition or subvolume on which the user should be able to use Snapper. Refer to Section 10.5, “Creating and modifying Snapper configurations” for instructions. Example:

    > sudo snapper --config web_data create /srv/www
  2. The configuration file is created under /etc/snapper/configs/CONFIG, where CONFIG is the value you specified with -c/--config in the previous step (for example /etc/snapper/configs/web_data). Adjust it according to your needs. For more information, see Section 10.5.1, “Managing existing configurations”.

  3. Set values for ALLOW_USERS and/or ALLOW_GROUPS to grant permissions to users and/or groups, respectively. Multiple entries need to be separated by Space. To grant permissions to the user www_admin for example, run:

    > sudo snapper -c web_data set-config "ALLOW_USERS=www_admin" SYNC_ACL="yes"
  4. The given Snapper configuration can now be used by the specified user(s) and/or group(s). You can test it with the list command, for example:

    www_admin:~ > snapper -c web_data list

10.6 Manually creating and managing snapshots

Snapper is not restricted to creating and managing snapshots automatically by configuration; you can also create snapshot pairs (before and after) or single snapshots manually using either the command-line tool or the YaST module.

All Snapper operations are carried out for an existing configuration (see Section 10.5, “Creating and modifying Snapper configurations” for details). You can only take snapshots of partitions or volumes for which a configuration exists. By default the system configuration (root) is used. To create or manage snapshots for your own configuration you need to explicitly choose it. Use the Current Configuration drop-down box in YaST or specify the -c on the command line (snapper -c MYCONFIG COMMAND).

10.6.1 Snapshot metadata

Each snapshot consists of the snapshot itself and certain metadata. When creating a snapshot you also need to specify the metadata. Modifying a snapshot means changing its metadata—you cannot modify its content. Use snapper list to show existing snapshots and their metadata:

snapper --config home list

Lists snapshots for the configuration home. To list snapshots for the default configuration (root), use snapper -c root list or snapper list.

snapper list -a

Lists snapshots for all existing configurations.

snapper list -t pre-post

Lists all pre and post snapshot pairs for the default (root) configuration.

snapper list -t single

Lists all snapshots of the type single for the default (root) configuration.

The following metadata is available for each snapshot:

  • Type: snapshot type, see Section 10.6.1.1, “Snapshot types” for details. This data cannot be changed.

  • Number: unique number of the snapshot. This data cannot be changed.

  • Pre Number: specifies the number of the corresponding pre snapshot. For snapshots of type post only. This data cannot be changed.

  • Description: a description of the snapshot.

  • Userdata: an extended description where you can specify custom data in the form of a comma-separated key=value list: reason=testing, project=foo. This field is also used to mark a snapshot as important (important=yes) and to list the user that created the snapshot (user=tux).

  • Cleanup-Algorithm: cleanup-algorithm for the snapshot, see Section 10.7, “Automatic snapshot clean-up” for details.

10.6.1.1 Snapshot types

Snapper knows three different types of snapshots: pre, post and single. Physically they do not differ, but Snapper handles them differently.

pre

Snapshot of a file system before a modification. Each pre snapshot corresponds to a post snapshot. For example, this is used for the automatic YaST/Zypper snapshots.

post

Snapshot of a file system after a modification. Each post snapshot corresponds to a pre snapshot. For example, this is used for the automatic YaST/Zypper snapshots.

single

Stand-alone snapshot. For example, this is used for the automatic hourly snapshots. This is the default type when creating snapshots.

10.6.1.2 Cleanup algorithms

Snapper provides three algorithms to clean up old snapshots. The algorithms are executed in a daily cron job. It is possible to define the number of different types of snapshots to keep in the Snapper configuration (see Section 10.5.1, “Managing existing configurations” for details).

number

Deletes old snapshots when a certain snapshot count is reached.

timeline

Deletes old snapshots having passed a certain age but keeps several hourly, daily, monthly and yearly snapshots.

empty-pre-post

Deletes pre/post snapshot pairs with empty diffs.

10.6.2 Creating snapshots

To create a snapshot, run snapper create or click Create in the YaST module Snapper. The following examples explain how to create snapshots from the command line. The YaST interface for Snapper is not explicitly described here but provides equivalent functionality.

Tip
Tip: Snapshot description

Always specify a meaningful description to later be able to identify its purpose. You can also specify additional information via the option --userdata.

snapper create --from 17 --description "with package2"

Creates a stand-alone snapshot (type single) from an existing snapshot, which is specified by the snapshot's number from snapper list. (This applies to Snapper version 0.8.4 and newer.)

snapper create --description "Snapshot for week 2 2014"

Creates a stand-alone snapshot (type single) for the default (root) configuration with a description. Because no cleanup-algorithm is specified, the snapshot will never be deleted automatically.

snapper --config home create --description "Cleanup in ~tux"

Creates a stand-alone snapshot (type single) for a custom configuration named home with a description. Because no cleanup-algorithm is specified, the snapshot will never be deleted automatically.

snapper --config home create --description "Daily data backup" --cleanup-algorithm timeline>

Creates a stand-alone snapshot (type single) for a custom configuration named home with a description. The snapshot will automatically be deleted when it meets the criteria specified for the timeline cleanup-algorithm in the configuration.

snapper create --type pre --print-number --description "Before the Apache config cleanup" --userdata "important=yes"

Creates a snapshot of the type pre and prints the snapshot number. First command needed to create a pair of snapshots used to save a before and after state. The snapshot is marked as important.

snapper create --type post --pre-number 30 --description "After the Apache config cleanup" --userdata "important=yes"

Creates a snapshot of the type post paired with the pre snapshot number 30. Second command needed to create a pair of snapshots used to save a before and after state. The snapshot is marked as important.

snapper create --command COMMAND --description "Before and after COMMAND"

Automatically creates a snapshot pair before and after running COMMAND. This option is only available when using snapper on the command line.

10.6.3 Modifying snapshot metadata

Snapper allows you to modify the description, the cleanup algorithm, and the user data of a snapshot. All other metadata cannot be changed. The following examples explain how to modify snapshots from the command line. It should be easy to adopt them when using the YaST interface.

To modify a snapshot on the command line, you need to know its number. Use snapper list to display all snapshots and their numbers.

The YaST Snapper module already lists all snapshots. Choose one from the list and click Modify.

snapper modify --cleanup-algorithm "timeline" 10

Modifies the metadata of snapshot 10 for the default (root) configuration. The cleanup algorithm is set to timeline.

snapper --config home modify --description "daily backup" -cleanup-algorithm "timeline" 120

Modifies the metadata of snapshot 120 for a custom configuration named home. A new description is set and the cleanup algorithm is unset.

10.6.4 Deleting snapshots

To delete a snapshot with the YaST Snapper module, choose a snapshot from the list and click Delete.

To delete a snapshot with the command-line tool, you need to know its number. Get it by running snapper list. To delete a snapshot, run snapper delete NUMBER.

Deleting the current default subvolume snapshot is not allowed.

When deleting snapshots with Snapper, the freed space will be claimed by a Btrfs process running in the background. Thus the visibility and the availability of free space is delayed. In case you need space freed by deleting a snapshot to be available immediately, use the option --sync with the delete command.

Tip
Tip: Deleting snapshot pairs

When deleting a pre snapshot, you should always delete its corresponding post snapshot (and vice versa).

snapper delete 65

Deletes snapshot 65 for the default (root) configuration.

snapper -c home delete 89 90

Deletes snapshots 89 and 90 for a custom configuration named home.

snapper delete --sync 23

Deletes snapshot 23 for the default (root) configuration and makes the freed space available immediately.

Tip
Tip: Delete unreferenced snapshots

Sometimes the Btrfs snapshot is present but the XML file containing the metadata for Snapper is missing. In this case the snapshot is not visible for Snapper and needs to be deleted manually:

btrfs subvolume delete /.snapshots/SNAPSHOTNUMBER/snapshot
rm -rf /.snapshots/SNAPSHOTNUMBER
Tip
Tip: Old snapshots occupy more disk space

If you delete snapshots to free space on your hard disk, make sure to delete old snapshots first. The older a snapshot is, the more disk space it occupies.

Snapshots are also automatically deleted by a daily cron job. Refer to Section 10.6.1.2, “Cleanup algorithms” for details.

10.7 Automatic snapshot clean-up

Snapshots occupy disk space and over time the amount of disk space occupied by the snapshots may become large. To prevent disks from running out of space, Snapper offers algorithms to automatically delete old snapshots. These algorithms differentiate between timeline snapshots and numbered snapshots (administration plus installation snapshot pairs). You can specify the number of snapshots to keep for each type.

Additionally, you can optionally specify a disk space quota, defining the maximum amount of disk space the snapshots may occupy. It is also possible to automatically delete pre and post snapshots pairs that do not differ.

A clean-up algorithm is always bound to a single Snapper configuration, so you need to configure algorithms for each configuration. To prevent certain snapshots from being automatically deleted, refer to Can a snapshot be protected from deletion? .

The default setup (root) is configured to do clean-up for numbered snapshots and empty pre and post snapshot pairs. Quota support is enabled—snapshots may not occupy more than 50% of the available disk space of the root partition. Timeline snapshots are disabled by default, therefore the timeline clean-up algorithm is also disabled.

10.7.1 Cleaning up numbered snapshots

Cleaning up numbered snapshots—administration plus installation snapshot pairs—is controlled by the following parameters of a Snapper configuration.

NUMBER_CLEANUP

Enables or disables clean-up of installation and admin snapshot pairs. If enabled, snapshot pairs are deleted when the total snapshot count exceeds a number specified with NUMBER_LIMIT and/or NUMBER_LIMIT_IMPORTANT and an age specified with NUMBER_MIN_AGE. Valid values: yes (enable), no (disable).

The default value is "yes".

Example command to change or set:

> sudo snapper -c CONFIG set-config "NUMBER_CLEANUP=no"
NUMBER_LIMIT / NUMBER_LIMIT_IMPORTANT

Defines how many regular and/or important installation and administration snapshot pairs to keep. Ignored if NUMBER_CLEANUP is set to "no".

The default value is "2-10" for NUMBER_LIMIT and "4-10" for NUMBER_LIMIT_IMPORTANT. The cleaning algorithms delete snapshots above the specified maximum value, without taking the snapshot and file system space into account. The algorithms also delete snapshots above the minimum value until the limits for the snapshot and file system are reached.

Example command to change or set:

> sudo snapper -c CONFIG set-config "NUMBER_LIMIT=10"
Important
Important: Ranged compared to constant values

In case quota support is enabled (see Section 10.7.5, “Adding disk quota support”) the limit needs to be specified as a minimum-maximum range, for example 2-10. If quota support is disabled, a constant value, for example 10, needs to be provided, otherwise cleaning-up will fail with an error.

NUMBER_MIN_AGE

Defines the minimum age in seconds a snapshot must have before it can automatically be deleted. Snapshots younger than the value specified here will not be deleted, regardless of how many exist.

The default value is "1800".

Example command to change or set:

> sudo snapper -c CONFIG set-config "NUMBER_MIN_AGE=864000"
Note
Note: Limit and age

NUMBER_LIMIT, NUMBER_LIMIT_IMPORTANT and NUMBER_MIN_AGE are always evaluated. Snapshots are only deleted when all conditions are met.

If you always want to keep the number of snapshots defined with NUMBER_LIMIT* regardless of their age, set NUMBER_MIN_AGE to 0.

The following example shows a configuration to keep the last 10 important and regular snapshots regardless of age:

NUMBER_CLEANUP=yes
NUMBER_LIMIT_IMPORTANT=10
NUMBER_LIMIT=10
NUMBER_MIN_AGE=0

If you do not want to keep snapshots beyond a certain age, set NUMBER_LIMIT* to 0 and provide the age with NUMBER_MIN_AGE.

The following example shows a configuration to only keep snapshots younger than ten days:

NUMBER_CLEANUP=yes
NUMBER_LIMIT_IMPORTANT=0
NUMBER_LIMIT=0
NUMBER_MIN_AGE=864000

10.7.2 Cleaning up timeline snapshots

Cleaning up timeline snapshots is controlled by the following parameters of a Snapper configuration.

TIMELINE_CLEANUP

Enables or disables clean-up of timeline snapshots. If enabled, snapshots are deleted when the total snapshot count exceeds a number specified with TIMELINE_LIMIT_* and an age specified with TIMELINE_MIN_AGE. Valid values: yes, no.

The default value is "yes".

Example command to change or set:

> sudo snapper -c CONFIG set-config "TIMELINE_CLEANUP=yes"
TIMELINE_LIMIT_DAILY, TIMELINE_LIMIT_HOURLY, TIMELINE_LIMIT_MONTHLY, TIMELINE_LIMIT_WEEKLY, TIMELINE_LIMIT_YEARLY

Number of snapshots to keep for hour, day, month, week and year.

The default value for each entry is "10", except for TIMELINE_LIMIT_WEEKLY, which is set to "0" by default.

TIMELINE_MIN_AGE

Defines the minimum age in seconds a snapshot must have before it can automatically be deleted.

The default value is "1800".

Example 10.1: Example timeline configuration
TIMELINE_CLEANUP="yes"
TIMELINE_CREATE="yes"
TIMELINE_LIMIT_DAILY="7"
TIMELINE_LIMIT_HOURLY="24"
TIMELINE_LIMIT_MONTHLY="12"
TIMELINE_LIMIT_WEEKLY="4"
TIMELINE_LIMIT_YEARLY="2"
TIMELINE_MIN_AGE="1800"

This example configuration enables hourly snapshots which are automatically cleaned up. TIMELINE_MIN_AGE and TIMELINE_LIMIT_* are always both evaluated. In this example, the minimum age of a snapshot before it can be deleted is set to 30 minutes (1800 seconds). Since we create hourly snapshots, this ensures that only the latest snapshots are kept. If TIMELINE_LIMIT_DAILY is set to not zero, this means that the first snapshot of the day is kept, too.

Snapshots to be kept
  • Hourly: the last 24 snapshots that have been made.

  • Daily: the first daily snapshot that has been made is kept from the last seven days.

  • Monthly: the first snapshot made on the last day of the month is kept for the last twelve months.

  • Weekly: the first snapshot made on the last day of the week is kept from the last four weeks.

  • Yearly: the first snapshot made on the last day of the year is kept for the last two years.

10.7.3 Cleaning up snapshot pairs that do not differ

As explained in Section 10.1.2, “Types of snapshots”, whenever you run a YaST module or execute Zypper, a pre snapshot is created on start-up and a post snapshot is created when exiting. In case you have not made any changes there will be no difference between the pre and post snapshots. Such empty snapshot pairs can be automatically be deleted by setting the following parameters in a Snapper configuration:

EMPTY_PRE_POST_CLEANUP

If set to yes, pre and post snapshot pairs that do not differ will be deleted.

The default value is "yes".

EMPTY_PRE_POST_MIN_AGE

Defines the minimum age in seconds a pre and post snapshot pair that does not differ must have before it can automatically be deleted.

The default value is "1800".

10.7.4 Cleaning up manually created snapshots

Snapper does not offer custom clean-up algorithms for manually created snapshots. However, you can assign the number or timeline clean-up algorithm to a manually created snapshot. If you do so, the snapshot will join the clean-up queue for the algorithm you specified. You can specify a clean-up algorithm when creating a snapshot, or by modifying an existing snapshot:

snapper create --description "Test" --cleanup-algorithm number

Creates a stand-alone snapshot (type single) for the default (root) configuration and assigns the number clean-up algorithm.

snapper modify --cleanup-algorithm "timeline" 25

Modifies the snapshot with the number 25 and assigns the clean-up algorithm timeline.

10.7.5 Adding disk quota support

In addition to the number and/or timeline clean-up algorithms described above, Snapper supports quotas. You can define what percentage of the available space snapshots are allowed to occupy. This percentage value always applies to the Btrfs subvolume defined in the respective Snapper configuration.

Btrfs quotas are applied to subvolumes, not to users. You may apply disk space quotas to users and groups (for example, with the quota command) in addition to using Btrfs quotas.

If Snapper was enabled during the installation, quota support is automatically enabled. In case you manually enable Snapper at a later point in time, you can enable quota support by running snapper setup-quota. This requires a valid configuration (see Section 10.5, “Creating and modifying Snapper configurations” for more information).

Quota support is controlled by the following parameters of a Snapper configuration.

QGROUP

The Btrfs quota group used by Snapper. If not set, run snapper setup-quota. If already set, only change if you are familiar with man 8 btrfs-qgroup. This value is set with snapper setup-quota and should not be changed.

SPACE_LIMIT

Limit of space snapshots are allowed to use in fractions of 1 (100%). Valid values range from 0 to 1 (0.1 = 10%, 0.2 = 20%, ...).

The following limitations and guidelines apply:

  • Quotas are only activated in addition to an existing number and/or timeline clean-up algorithm. If no clean-up algorithm is active, quota restrictions are not applied.

  • With quota support enabled, Snapper will perform two clean-up runs if required. The first run will apply the rules specified for number and timeline snapshots. Only if the quota is exceeded after this run, the quota-specific rules will be applied in a second run.

  • Even if quota support is enabled, Snapper will always keep the number of snapshots specified with the NUMBER_LIMIT* and TIMELINE_LIMIT* values, even if the quota will be exceeded. It is therefore recommended to specify ranged values (MIN-MAX) for NUMBER_LIMIT* and TIMELINE_LIMIT* to ensure the quota can be applied.

    If, for example, NUMBER_LIMIT=5-20 is set, Snapper will perform a first clean-up run and reduce the number of regular numbered snapshots to 20. In case these 20 snapshots exceed the quota, Snapper will delete the oldest ones in a second run until the quota is met. A minimum of five snapshots will always be kept, regardless of the amount of space they occupy.

10.8 Showing exclusive disk space used by snapshots

Snapshots share data, for efficient use of storage space, so using ordinary commands like du and df will not measure used disk space accurately. When you want to free up disk space on Btrfs with quotas enabled, you need to know how much exclusive disk space is used by each snapshot, rather than shared space. Snapper 0.6 and up reports the used disk space for each snapshot in the Used Space column:

# snapper--iso list
  # | Type   | Pre # | Date                | User | Used Space | Cleanup | Description           | Userdata     
----+--------+-------+---------------------+------+------------+---------+-----------------------+--------------
 0  | single |       |                     | root |            |         | current               |              
 1* | single |       | 2019-07-22 13:08:38 | root |  16.00 KiB |         | first root filesystem |              
 2  | single |       | 2019-07-22 14:21:05 | root |  14.23 MiB | number  | after installation    | important=yes
 3  | pre    |       | 2019-07-22 14:26:03 | root | 144.00 KiB | number  | zypp(zypper)          | important=no 
 4  | post   |     3 | 2019-07-22 14:26:04 | root | 112.00 KiB | number  |                       | important=no 
 5  | pre    |       | 2019-07-23 08:19:36 | root | 128.00 KiB | number  | zypp(zypper)          | important=no 
 6  | post   |     5 | 2019-07-23 08:19:43 | root |  80.00 KiB | number  |                       | important=no 
 7  | pre    |       | 2019-07-23 08:20:50 | root | 256.00 KiB | number  | yast sw_single        |              
 8  | pre    |       | 2019-07-23 08:23:22 | root | 112.00 KiB | number  | zypp(ruby.ruby2.5)    | important=no 
 9  | post   |     8 | 2019-07-23 08:23:35 | root |  64.00 KiB | number  |                       | important=no 
10  | post   |     7 | 2019-07-23 08:24:05 | root |  16.00 KiB | number  |                       |

The btrfs command provides another view of space used by snapshots:

# btrfs qgroup show -p /
qgroupid         rfer         excl parent  
--------         ----         ---- ------  
0/5          16.00KiB     16.00KiB ---     
[...]    
0/272         3.09GiB     14.23MiB 1/0     
0/273         3.11GiB    144.00KiB 1/0     
0/274         3.11GiB    112.00KiB 1/0     
0/275         3.11GiB    128.00KiB 1/0     
0/276         3.11GiB     80.00KiB 1/0     
0/277         3.11GiB    256.00KiB 1/0     
0/278         3.11GiB    112.00KiB 1/0     
0/279         3.12GiB     64.00KiB 1/0     
0/280         3.12GiB     16.00KiB 1/0     
1/0           3.33GiB    222.95MiB ---

The qgroupid column displays the identification number for each subvolume, assigning a qgroup level/ID combination.

The rfer column displays the total amount of data referred to in the subvolume.

The excl column displays the exclusive data in each subvolume.

The parent column shows the parent qgroup of the subvolumes.

The final item, 1/0, shows the totals for the parent qgroup. In the above example, 222.95 MiB will be freed if all subvolumes are removed. Run the following command to see which snapshots are associated with each subvolume:

# btrfs subvolume list -st /
ID	gen	top level	path	
--	---	---------	----	
267	298	266		@/.snapshots/1/snapshot
272	159	266		@/.snapshots/2/snapshot
273	170	266		@/.snapshots/3/snapshot
274	171	266		@/.snapshots/4/snapshot
275	287	266		@/.snapshots/5/snapshot
276	288	266		@/.snapshots/6/snapshot
277	292	266		@/.snapshots/7/snapshot
278	296	266		@/.snapshots/8/snapshot
279	297	266		@/.snapshots/9/snapshot
280	298	266		@/.snapshots/10/snapshot

Doing an upgrade from one service pack to another results in snapshots occupying a lot of disk space on the system subvolumes. Manually deleting these snapshots after they are no longer needed is recommended. See Section 10.6.4, “Deleting snapshots” for details.

10.9 Frequently asked questions

Q: Why does Snapper never show changes in /var/log, /tmp and other directories?

For certain directories, we decided to exclude them from snapshots. See Section 10.1.3, “Directories that are excluded from snapshots” for a list and reasons. To exclude a path from snapshots we create a subvolume for that path.

Q: Can I boot a snapshot from the boot loader?

Yes—refer to Section 10.3, “System rollback by booting from snapshots” for details.

Q: Can a snapshot be protected from deletion?

Currently Snapper does not offer means to prevent a snapshot from being deleted manually. However, you can prevent snapshots from being automatically deleted by clean-up algorithms. Manually created snapshots (see Section 10.6.2, “Creating snapshots”) have no clean-up algorithm assigned unless you specify one with --cleanup-algorithm. Automatically created snapshots always either have the number or timeline algorithm assigned. To remove such an assignment from one or more snapshots, proceed as follows:

  1. List all available snapshots:

    > sudo snapper list -a
  2. Memorize the number of the snapshots you want to prevent from being deleted.

  3. Run the following command and replace the number placeholders with the number(s) you memorized:

    > sudo snapper modify --cleanup-algorithm "" #1 #2 #n
  4. Check the result by running snapper list -a again. The entry in the column Cleanup should now be empty for the snapshots you modified.

Q: Where can I get more information on Snapper?

See the Snapper home page at http://snapper.io/.

11 Live kernel patching with KLP

This document describes the basic principles of the Kernel Live Patching (KLP) technology, and provides usage guidelines for the SLE Live Patching service.

KLP makes it possible to apply the latest security updates to Linux kernels without rebooting. This maximizes system uptime and availability, which is especially important for mission-critical systems.

The information provided in this document relates to the AMD64/Intel 64, POWER, and IBM Z architectures.

11.1 Advantages of Kernel Live Patching

KLP offers several benefits.

  • Keeping a large number of servers automatically up to date is essential for organizations obtaining or maintaining certain compliance certifications. KLP can help achieve compliance, while reducing the need for costly maintenance windows.

  • Companies that work with service-level agreement contracts must guarantee a specific level of their system accessibility and uptime. Live patching makes it possible to patch systems without incurring downtime.

  • Since KLP is part of the standard system update mechanism, there is no need for specialized training or introduction of complicated maintenance routines.

11.2 Kernel Live Patching overview

Kernel live patches are delivered as packages with modified code that are separate from the main kernel package. The live patches are cumulative, so the latest patch contains all fixes from the previous ones for the kernel package. Each kernel live package is tied to the exact kernel revision for which it is issued. The live patch package version number increases with every addition of fixes.

Note
Note: Live patches and the running kernel

To determine the kernel patching status, use the klp -v patches command. The uname command's output does not change for patched kernels.

Important
Important: Live patches compared to kernel updates

Live patches contain only critical fixes, and they do not replace regular kernel updates that require a reboot. Consider live patches as temporary measures that protect the kernel until a proper kernel update and a reboot are performed.

The diagram below illustrates the overall relationship between live patches and kernel updates. The list of CVEs and defect reports addressed by the currently active live patch can be viewed using the klp -v patches command.

Image

It is possible to have multiple versions of the kernel package installed along with their live patches. These packages do not conflict. You can install updated kernel packages along with live patches for the running kernel. In this case, you may be prompted to reboot the system. Users with SLE Live Patching subscriptions are eligible for technical support as long as there are live patch updates for the running kernel (see Section 11.5.1, “Checking expiration date of the live patch”).

With KLP activated, every kernel update comes with a live patch package. This live patch does not contain any fixes and serves as a seed for future live patches for the corresponding kernel. These empty seed patches are called initial patches.

11.2.1 Kernel Live Patching scope

The scope of SLE Live Patching includes fixes for SUSE Common Vulnerability Scoring System (CVSS; SUSE CVSS is based on the CVSS v3.0 system) level 7+ vulnerabilities and bug fixes related to system stability or data corruption. However, it may not be technically feasible to create live patches for all fixes that fall under the specified categories. SUSE therefore reserves the right to skip fixes in situations where creating a kernel live patch is not possible for technical reasons. Currently, over 95% of qualifying fixes are released as live patches. For more information on CVSS (the base for the SUSE CVSS rating), see Common Vulnerability Scoring System SIG.

11.2.2 Kernel Live Patching limitations

KLP involves replacing functions and gracefully handling replacement of interdependent function sets. This is done by redirecting calls to old code to updated code in a different memory location. Changes in data structures make the situation more complicated, as the data remain in place and cannot be extended or reinterpreted. While there are techniques that allow indirect alteration of data structures, certain fixes cannot be converted to live patches. In this situation, a system restart is the only way to apply the fixes.

11.3 Activating Kernel Live Patching using YaST

To activate KLP on your system, you need to have active SLES and SLE Live Patching subscriptions. Visit SUSE Customer Center to check the status of your subscriptions and obtain a registration code for the SLE Live Patching subscription.

To activate Kernel Live Patching on your system, follow these steps:

  1. Run the yast2 registration command and click Select Extensions.

  2. Select SUSE Linux Enterprise Live Patching 15 in the list of available extensions and click Next.

  3. Confirm the license terms and click Next.

  4. Enter your SLE Live Patching registration code and click Next.

  5. Check the Installation Summary and selected Patterns. The patterns Live Patching and SLE Live Patching Lifecycle Data should be automatically selected for installation along with additional packages to satisfy dependencies.

  6. Click Accept to complete the installation. This installs the base Kernel Live Patching components on your system, the initial live patch, and the required dependencies.

11.4 Activating Kernel Live Patching from the command line

To activate Kernel Live Patching, you need to have active SLES and SLES Live Patching subscriptions. Visit SUSE Customer Center to check the status of your subscriptions and obtain a registration code for the SLES Live Patching subscription.

  1. Run sudo SUSEConnect --list-extensions. Note the exact activation command for SLES Live Patching. Example command output (abbreviated):

    $ SUSEConnect --list-extensions
    ...
    SUSE Linux Enterprise Live Patching 15 SP5 x86_64
    Activate with: SUSEConnect -p sle-module-live-patching/15.5/x86_64 \
      -r ADDITIONAL REGCODE
  2. Activate SLES Live Patching using the obtained command followed by -r LIVE_PATCHING_REGISTRATION_CODE, for example:

    SUSEConnect -p sle-module-live-patching/15.5/x86_64 \
      -r LIVE_PATCHING_REGISTRATION_CODE
  3. Install the required packages and dependencies using the command zypper install -t pattern lp_sles

At this point, the system has already been live-patched.

Here is how the process works behind the scenes: when the package installation system detects that there is an installed kernel that can be live-patched, and that there is a live patch for it in the software channel, the system selects the live patch for installation. The kernel then receives the live patch fixes as part of the package installation. The kernel gets live-patched even before the product installation is complete.

11.5 Performing Kernel Live Patching

Kernel live patches are installed as part of regular system updates. However, there are several things you should be aware of.

  • The kernel is live-patched if a kernel-livepatch-* package has been installed for the running kernel. You can use the command zypper se --details kernel-livepatch-* to check what kernel live patch packages are installed on your system.

  • When the kernel-default package is installed, the update manager prompts you to reboot the system. To prevent this message from appearing, you can filter out kernel updates from the patching operation. This can be done by adding package locks with Zypper. SUSE Manager also makes it possible to filter channel contents (see Live Patching with SUSE Manager).

  • You can check patching status using the klp status command. To examine installed patches, run the klp -v patches command.

  • Keep in mind that while there may be multiple kernel packages installed on the system, only one of them is running at any given time. Similarly, there may be multiple live patch packages installed, but only one live patch is loaded into the kernel.

  • The active live patch is included in the initrd. This means that in case of an unexpected reboot, the system comes up with the live patch fixes applied, so there is no need to perform patching again.

11.5.1 Checking expiration date of the live patch

Make sure that the lifecycle-data-sle-module-live-patching is installed, then run the zypper lifecycle command. You should see expiration dates for live patches in the Package end of support if different from product section of the output.

Every live patch receives updates for one year from the release of the underlying kernel package. The Maintained kernels, patch updates and lifecycle page allows you to check expiration dates based on the running kernel version without installing the product extension.

11.6 Troubleshooting Kernel Live Patching issues

11.6.1 Manual patch downgrade

If you find the latest live patch problematic, you can downgrade the currently installed live patch back to its previous version. We recommend performing patch downgrade before the system starts exhibiting issues. Keep in mind that a system with kernel warnings or kernel error traces in the system log may not be suitable for the patch downgrade procedure. If you are unsure whether the system meets the requirements for a patch downgrade, contact SUSE Technical Support for help.

Procedure 11.1: Manual patch downgrade
  1. Identify the running live patch using the klp -v patches command. You can see the currently running patch on the line starting with RPM:. For example:

    RPM: kernel-livepatch-5_3_18-24_29-default-2-2.1.x86_64

    The 5_3_18-24_29-default in the example above denotes the exact running kernel version.

  2. Use the command zypper search -s kernel-livepatch-RUNNING_KERNEL_VERSION-default to search for previous versions of the patch. The command returns a list of available package versions. Keep in mind that for every new live patch package release, the version number increases by one. Make sure that you choose the version number one release lower than the current one.

  3. Install the desired version with the command zypper in --oldpackage kernel-livepatch-RUNNING_KERNEL_VERSION-default=DESIRED_VERSION.

12 User space live patching

This chapter describes the basic principles and usage of user space live patching.

12.1 About user space live patching

User space live patching (ULP) refers to the process of applying patches to the libraries used by a running process without interrupting them. Every time a security fix is available as a live patch, customer services will be secured after applying the live patch without restarting the processes.

Live patching operations are performed using the ulp tool that is part of libpulp. libpulp is a framework that consists of the libpulp.so library and the ulp binary that makes libraries live patchable and applies live patches.

Tip
Tip

You can run the ulp command either as a normal user or a privileged user via the sudo mechanism. The difference is that running ulp via sudo lets you view information of processes or patch processes that are running by root.

12.1.1 Prerequisites

For ULP to work, two requirements must be met.

  • Install the ULP on your system by running:

    > sudo zypper in libpulp0 libpulp-tools
  • Applications with desired live patch support must be launched preloading the libpulp.so.0 library. See Section 12.1.3, “Using libpulp for more details.

12.1.2 Supported libraries

Currently, only glibc and openssl (openssl1_1) are supported. Additional packages will be available after they are prepared for live patching. To receive glibc and openssl live patches, install both glibc-livepatches and openssl-livepatches packages:

> zypper install glibc-livepatches openssl-livepatches

12.1.3 Using libpulp

To enable live patching on an application, you need to preload the libpulp.so.0 library when starting the application:

> LD_PRELOAD=/usr/lib64/libpulp.so.0 APPLICATION_CMD

12.1.3.1 Checking if a library is live patchable

To check whether a library is live patchable, use the following command:

> ulp livepatchable PATH_TO_LIBRARY

12.1.3.2 Checking if a .so file is a live patch container

A shared object (.so) is a live patch container if it contains the ULP patch description embedded into it. You can verify it with the following command:

> readelf -S SHARED_OBJECT | grep .ulp

If the output shows that there are both .ulp and .ulp.rev sections in the shared object, then it is a live patch container.

12.1.3.3 Applying live patches

Live patches are applied using the ulp trigger command, for example:

> ulp trigger -p PID LIVEPATCH.so

Replace PID with the process ID of the running process that uses the library to be patched and LIVEPATCH.so with the actual live patch file. The command returns one of the following status messages:

SUCCESS

The live patching operation was successful.

SKIPPED

The patch was skipped because it was not designed for any library that is loaded in the process.

ERROR

An error occurred, and you can retrieve more information by inspecting the libpulp internal message buffer. See Section 12.1.3.6, “View internal message queue” for more information.

It is also possible to apply multiple live patches by using wildcards, for example:

> ulp trigger '*.so'

The command tries to apply every patch in the current folder to every process that have the libpulp library loaded. If the patch is not suitable for the process, it is automatically skipped. In the end, the tool shows how many patches it successfully applied to how many processes.

12.1.3.4 Reverting live patches

You can use the ulp trigger command to revert live patches. There are two ways to revert live patches. You can revert a live patch by using the --revert switch and passing the live patch container:

> ulp trigger -p PID --revert LIVEPATCH.so

Alternatively, it is possible to remove all patches associated with a particular library, for example:

> ulp trigger -p PID --revert-all=LIBRARY

In the example, LIBRARY refers to the actual library, such as libcrypto.so.1.1.

The latter approach can be useful when the source code of the original live patch is not available. Or you want to remove a specific old patch and apply a new one while the target application is still running a secure code, for example:

> ulp trigger -p PID  --revert-all=libcrypto.so.1.1 new_livepatch2.so

12.1.3.5 View applied patches

It is possible to verify which applications have live patches applied by running:

> ulp patches

The output shows which libraries are live patchable and patches loaded in programs, as well which bugs the patch addresses:

PID: 10636, name: test
  Livepatchable libraries:
    in /lib64/libc.so.6:
      livepatch: libc_livepatch1.so
        bug labels: jsc#SLE-0000
    in /usr/lib64/libpulp.so.0:

It is also possible to see which functions are patched by the live patch:

> ulp dump LIVEPATCH.so

12.1.3.6 View internal message queue

Log messages from libpulp.so are stored in a buffer inside the library and are not displayed unless requested by the user. To show these messages, run:

> ulp messages -p PID

12.2 More information

Further information about libpulp is available in the project's Git repository.

13 Transactional updates

Transactional updates are available in SUSE Linux Enterprise Server as a technology preview, for updating SLES when the root file system is read-only. Transactional updates are atomic (all updates are applied only if all updates succeed) and support rollbacks. It does not affect a running system as no changes are activated until after the system is rebooted. As reboots are disruptive, the administrator must decide if a reboot is more expensive than disturbing running services. If reboots are too expensive then do not use transactional updates.

Transactional updates are run daily by the transactional-update script. The script checks for available updates. If there are any updates, it creates a new snapshot of the root file system in the background, and then fetches updates from the release channels. After the new snapshot is completely updated, it is marked as active and will be the new default root file system after the next reboot of the system. When transactional-update is set to run automatically (which is the default behavior) it also reboots the system. Both the time that the update runs and the reboot maintenance window are configurable.

Only packages that are part of the snapshot of the root file system can be updated. If packages contain files that are not part of the snapshot, the update could fail or break the system.

RPMs that require a license to be accepted cannot be updated.

13.1 Limitations of technology preview

As a technology preview, there are certain limitations in functionality. The following packages will not work with transactional-update:

  • The nginx default index.html page may not be available

  • tomcat-webapps and tomcat-admin-webapps

  • phpMyAdmin

  • sca-appliance-*

  • mpi-selector

  • emacs works except for Emacs games

  • bind and bind-chrootenv

  • docbook*

  • sblim-sfcb*

  • texlive*

  • iso_ent

  • openjade

  • opensp

  • pcp

  • plymouth

  • postgresql-server-10

  • pulseaudio-gdm-hooks

  • smartmontools

The updater component of the system installer does not work with a read-only file system as it has no support for transactional updates.

Further considerations:

  • It is a good idea to minimize the time between updating the system and rebooting the machine.

  • Only one update can be applied at a time. Be sure to reboot after an update, and before the next update is applied.

  • update-alternatives should not be run after a transactional update until the machine has been rebooted.

  • Do not create new system users or system groups after a transactional update until after reboot. It is acceptable to create normal users and groups (UID > 1000, GID > 1000).

  • YaST is not yet aware of transactional updates. If a YaST module needs to install additional packages, this will not work. Normal system operations only modifying configuration files in /etc will work.

  • For php7-fastcgi, you must manually create a symbolic link, /srv/www/cgi-bin/php, that points to /usr/bin/php-cgi.

  • ntpis part of the Legacy Module for migration from older SLES versions. It is not supported on a new SUSE Linux Enterprise Server installation, and has been replaced by chrony. If you continue to use ntp, a fresh installation is required to work correctly with transactional updates.

  • sblim-sfcb: the whole sblim ecosystem is incompatible with transactional update.

  • btrfs-defrag from the btrfsmaintenance package does not work with a read-only root file system.

  • For btrfs-balance, the variable BTRFS_BALANCE_MOUNTPOINTS in /etc/sysconfig/btrfsmaintenance must be changed from / to /.snapshots.

  • For btrfs-scrub, the variable BTRFS_SCRUB_MOUNTPOINTS in /etc/sysconfig/btrfsmaintenance must be changed from / to /.snapshots.

13.2 Enabling transactional-update

You must enable the Transactional Server Module during system installation, and then select the Transactional Server System Role. Installing any package from the Transactional Server Module later in a running system is NOT supported and may break the system.

Changing the subvolume layout of the root partition, or putting sub-directories or subvolumes of the root partition on their own partitions (except /home, /var, /srv, and /opt) is not supported, and will most probably break the system.

13.3 Managing automatic updates

Automatic updates are controlled by a systemd.timer that runs once per day. This applies all updates, and informs rebootmgrd that the machine should be rebooted. You may adjust the time when the update runs, see systemd.timer(5). To adjust the maintenance window, which is when rebootmgrd reboots the system, see rebootmgrd(8).

You can disable automatic transactional updates with this command:

# systemctl --now disable transactional-update.timer

13.4 The transactional-update command

The transactional-update command enables atomic installation or removal of updates; updates are applied only if all of them can be successfully installed. transactional-update creates a snapshot of your system before the update is applied, and you can restore this snapshot. All changes become active only after reboot.

--continue

The --continue option is for making multiple changes to an existing snapshot without rebooting.

The default transactional-update behavior is to create a new snapshot from the current root file system. If you forget something, such as installing a new package, you have to reboot to apply your previous changes, run transactional-update again to install the forgotten package, and reboot again. You cannot run the transactional-update command multiple times without rebooting to add more changes to the snapshot, because that creates separate independent snapshots that do not include changes from the previous snapshots.

Use the --continue option to make as many changes as you want without rebooting. A separate snapshot is made each time, and each snapshot contains all the changes you made in the previous snapshots, plus your new changes. Repeat this process as many times as you want, and when the final snapshot includes everything you want reboot the system, and your final snapshot becomes the new root file system.

Another useful feature of the --continue option is you may select any existing snapshot as the base for your new snapshot. The following example demonstrates running transactional-update to install a new package in a snapshot based on snapshot 13, and then running it again to install another package:

# transactional-update pkg install package_1
# transactional-update --continue 13 pkg install package_2

The --continue [num] option calls snapper create --from, see Section 10.6.2, “Creating snapshots”.

cleanup

If the current root file system is identical to the active root file system (after a reboot, before transactional-update creates a new snapshot with updates), all old snapshots without a cleanup algorithm get a cleanup algorithm set. This ensures that old snapshots will be deleted by Snapper. (See the section about cleanup algorithms in snapper(8).) This also removes all unreferenced (and thus unused) /etc overlay directories in /var/lib/overlay:

# transactional-update cleanup
pkg in/install

Installs individual packages from the available channels using the zypper install command. This command can also be used to install Program Temporary Fix (PTF) RPM files.

# transactional-update pkg install package_name

or

# transactional-update pkg install rpm1 rpm2
pkg rm/remove

Removes individual packages from the active snapshot using the zypper remove command. This command can also be used to remove PTF RPM files.

# transactional-update pkg remove package_name
pkg up/update

Updates individual packages from the active snapshot using the zypper update command. Only packages that are part of the snapshot of the base file system can be updated.

# transactional-update pkg update package_name
up/update

If there are new updates available, a new snapshot is created and zypper up/update updates the snapshot.

# transactional-update up
dup

If there are new updates available, a new snapshot is created and zypper dup –no-allow-vendor-change updates the snapshot. The snapshot is activated afterwards and becomes the new root file system after reboot.

# transactional-update dup
patch

If there are new updates available, a new snapshot is created and zypper patch updates the snapshot.

# transactional-update patch
rollback

This sets the default subvolume. On systems with a read-write file system snapper rollback is called. On a read-only file system and without any argument, the current system is set to a new default root file system. If you specify a number, that snapshot is used as the default root file system. On a read-only file system, it does not create any additional snapshots.

# transactional-update rollback snapshot_number
grub.cfg

This creates a new GRUB2 configuration. Sometimes it is necessary to adjust the boot configuration, for example adding additional kernel parameters. Edit /etc/default/grub, run transactional-update grub.cfg, and then reboot to activate the change. You must immediately reboot, or the new GRUB2 configuration will be overwritten with the default by the next transactional-update.

# transactional-update grub.cfg
reboot

This parameter triggers a reboot after the action is completed.

# transactional-update dup reboot
--help

This prints a help screen with options and subcommands.

# transactional-update --help

13.5 Troubleshooting

If the upgrade fails, run supportconfig to collect log data. Provide the resulting files, including /var/log/transactional-update.log to SUSE Support.

14 Remote graphical sessions with VNC

Virtual Network Computing (VNC) enables you to access a remote computer via a graphical desktop, and run remote graphical applications. VNC is platform-independent and accesses the remote machine from any operating system. This chapter describes how to connect to a VNC server with the desktop clients vncviewer and Remmina, and how to operate a VNC server.

SUSE Linux Enterprise Server supports two different kinds of VNC sessions: one-time sessions that live While the VNC connection from the client is kept up, and persistent sessions that live until they are explicitly terminated.

A VNC server can offer both kinds of sessions simultaneously on different ports, but an open session cannot be converted from one type to the other.

14.1 The vncviewer client

To connect to a VNC service provided by a server, a client is needed. The default in SUSE Linux Enterprise Server is vncviewer, provided by the tigervnc package.

14.1.1 Connecting using the vncviewer CLI

To start your VNC viewer and initiate a session with the server, use the command:

> vncviewer jupiter.example.com:1

Instead of the VNC display number you can also specify the port number with two colons:

> vncviewer jupiter.example.com::5901
Note
Note: Display and port number

The actual display or port number you specify in the VNC client must be the same as the display or port number selected when configuring a VNC server on the target machine. See Section 14.4, “Configuring persistent VNC server sessions” for further info.

14.1.2 Connecting using the vncviewer GUI

When running vncviewer without specifying --listen or a host to connect to, it shows a window asking for connection details. Enter the host into the VNC server field like in Section 14.1.1, “Connecting using the vncviewer CLI” and click Connect.

vncviewer asking for connection details
Figure 14.1: vncviewer

14.1.3 Notification of unencrypted connections

The VNC protocol supports different kinds of encrypted connections, not to be confused with password authentication. If a connection does not use TLS, the text (Connection not encrypted!) can be seen in the window title of the VNC viewer.

14.2 Remmina: the remote desktop client

Remmina is a modern and feature rich remote desktop client. It supports several access methods, for example VNC, SSH, RDP and Spice.

14.2.1 Installation

To use Remmina, verify whether the remmina package is installed on your system, and install it if not. Remember to install the VNC plug-in for Remmina as well:

# zypper in remmina remmina-plugin-vnc

14.2.2 Main window

Run Remmina by entering the remmina command.

Remmina's main window
Figure 14.2: Remmina's main window

The main application window shows the list of stored remote sessions. Here you can add and save a new remote session, quick-start a new session without saving it, start a previously saved session, or set Remmina's global preferences.

14.2.3 Adding remote sessions

To add and save a new remote session, click Add new session in the top left of the main window. The Remote Desktop Preference window opens.

Remote desktop preference
Figure 14.3: Remote desktop preference

Complete the fields that specify your newly added remote session profile. The most important are:

Name

Name of the profile. It will be listed in the main window.

Protocol

The protocol to use when connecting to the remote session, for example VNC.

Server

The IP or DNS address and display number of the remote server.

User name, password

Credentials to use for remote authentication. Leave empty for no authentication.

Color depth, quality

Select the best options according to your connection speed and quality.

Select the Advanced tab to enter more specific settings.

Tip
Tip: Disable encryption

If the communication between the client and the remote server is not encrypted, activate Disable encryption, otherwise the connection fails.

Select the SSH tab for advanced SSH tunneling and authentication options.

Confirm with Save. Your new profile will be listed in the main window.

14.2.4 Starting remote sessions

You can either start a previously saved session, or quick-start a remote session without saving the connection details.

14.2.4.1 Quick-starting remote sessions

To start a remote session quickly without adding and saving connection details, use the drop-down box and text box at the top of the main window.

Quick-starting
Figure 14.4: Quick-starting

Select the communication protocol from the drop-down box, for example VNC, then enter the VNC server DNS or IP address followed by a colon and a display number, and confirm with Enter.

14.2.4.2 Opening saved remote sessions

To open a specific remote session, double-click it from the list of sessions.

14.2.4.3 Remote sessions window

Remote sessions are opened in tabs of a separate window. Each tab hosts one session. The toolbar on the left of the window helps you manage the windows/sessions. For example, toggle full-screen mode, resize the window to match the display size of the session, send specific keystrokes to the session, take screenshots of the session, or set the image quality.

Remmina viewing remote session
Figure 14.5: Remmina viewing remote session

14.2.5 Editing, copying, and deleting saved sessions

To edit a saved remote session, right-click its name in Remmina's main window and select Edit. Refer to Section 14.2.3, “Adding remote sessions” for the description of the relevant fields.

To copy a saved remote session, right-click its name in Remmina's main window and select Copy. In the Remote Desktop Preference window, change the name of the profile, optionally adjust relevant options, and confirm with Save.

To Delete a saved remote session, right-click its name in Remmina's main window and select Delete. Confirm with Yes in the next dialog.

14.2.6 Running remote sessions from the command line

If you need to open a remote session from the command line or from a batch file without first opening the main application window, use the following syntax:

 > remmina -c profile_name.remmina

Remmina's profile files are stored in the .local/share/remmina/ directory in your home directory. To determine which profile file belongs to the session you want to open, run Remmina, click the session name in the main window, and read the path to the profile file in the window's status line at the bottom.

Reading path to the profile file
Figure 14.6: Reading path to the profile file

While Remmina is not running, you can rename the profile file to a more reasonable file name, such as sle15.remmina. You can even copy the profile file to your custom directory and run it using the remmina -c command from there.

14.3 Configuring one-time sessions on the VNC server

A one-time session is initiated by the remote client. It starts a graphical login screen on the server. This way you can choose the user which starts the session and, if supported by the login manager, the desktop environment. When you cancel the client connection to such a VNC session, all applications started within that session will be terminated, too. One-time VNC sessions cannot be shared, but it is possible to have multiple sessions on a single host at the same time.

Procedure 14.1: Enabling one-time VNC sessions
  1. Start YaST › Network Services › Remote Administration (VNC).

  2. Check Allow Remote Administration Without Session Management.

  3. Activate Enable access using a web browser if you plan to access the VNC session in a Web browser window.

  4. If necessary, also check Open Port in Firewall (for example, when your network interface is configured to be in the External Zone). If you have more than one network interface, restrict opening the firewall ports to a specific interface via Firewall Details.

  5. Confirm your settings with Next.

  6. In case not all needed packages are available yet, you need to approve the installation of missing packages.

    Tip
    Tip: Restart the display manager

    YaST makes changes to the display manager settings. You need to log out of your current graphical session and restart the display manager for the changes to take effect.

Remote administration
Figure 14.7: Remote administration

14.3.1 Available configurations

The default configuration on SUSE Linux Enterprise Server serves sessions with a resolution of 1024x768 pixels at a color depth of 16-bit. The sessions are available on ports 5901 for regular VNC viewers (equivalent to VNC display 1) and on port 5801 for Web browsers.

Other configurations can be made available on different ports, see Section 14.3.3, “Configuring one-time VNC sessions”.

VNC display numbers and X display numbers are independent in one-time sessions. A VNC display number is manually assigned to every configuration that the server supports (:1 in the example above). Whenever a VNC session is initiated with one of the configurations, it automatically gets a free X display number.

By default, both the VNC client and server try to communicate securely via a self-signed SSL certificate, which is generated after installation. You can either use the default one, or replace it with your own. When using the self-signed certificate, you need to confirm its signature before the first connection—both in the VNC viewer and the Web browser.

Tip
Tip

Some VNC clients refuse to establish a secure connection via the default self-signed certificate. For example, the Vinagre client verifies the certification against the GnuTLS global trust store and fails if the certificate is self-signed. In such a case, either use an encryption method other than x509, or generate a properly signed certificate for the VNC server and import it to the client's system trust store.

14.3.2 Initiating a one-time VNC session

To connect to a one-time VNC session, a VNC viewer must be installed, see also Section 14.1, “The vncviewer client”. Alternatively use a JavaScript-capable Web browser to view the VNC session by entering the following URL: http://jupiter.example.com:5801

14.3.3 Configuring one-time VNC sessions

You can skip this section, if you do not need or want to modify the default configuration.

One-time VNC sessions are started via the systemd socket xvnc.socket. By default it offers six configuration blocks: three for VNC viewers (vnc1 to vnc3), and three serving a JavaScript client (vnchttpd1 to vnchttpd3). By default only vnc1 and vnchttpd1 are active.

To activate the VNC server socket at boot time, run the following command:

> sudo  systemctl enable xvnc.socket

To start the socket immediately, run:

> sudo  systemctl start xvnc.socket

The Xvnc server can be configured via the server_args option. For a list of options, see Xvnc --help.

When adding custom configurations, make sure they are not using ports that are already in use by other configurations, other services, or existing persistent VNC sessions on the same host.

Activate configuration changes by entering the following command:

> sudo systemctl reload xvnc.socket
Important
Important: Firewall and VNC ports

When activating Remote Administration as described in Procedure 14.1, “Enabling one-time VNC sessions”, the ports 5801 and 5901 are opened in the firewall. If the network interface serving the VNC sessions is protected by a firewall, you need to manually open the respective ports when activating additional ports for VNC sessions. See Book “Security and Hardening Guide”, Chapter 23 “Masquerading and firewalls” for instructions.

14.4 Configuring persistent VNC server sessions

A persistent session can be accessed from multiple clients simultaneously. This is ideal for demonstration purposes where one client has full access and all other clients have view-only access. Another use case are training sessions where the trainer may need access to the trainee's desktop.

Tip
Tip: Connecting to a persistent VNC session

To connect to a persistent VNC session, a VNC viewer must be installed. Refer to Section 14.1, “The vncviewer client” for more details. Alternatively, use a JavaScript-capable Web browser to view the VNC session by entering the following URL: http://jupiter.example.com:5801.

14.4.1 VNC session initiated using vncmanager

Procedure 14.2: Enabling persistent VNC sessions
  1. Start YaST › Network Services › Remote Administration (VNC).

  2. Activate Allow Remote Administration With Session Management.

  3. Activate Enable access using a web browser if you plan to access the VNC session in a Web browser window.

  4. If necessary, also check Open Port in Firewall (for example, when your network interface is configured to be in the External Zone). If you have more than one network interface, restrict opening the firewall ports to a specific interface via Firewall Details.

  5. Confirm your settings with Next.

  6. In case not all needed packages are available yet, you need to approve the installation of missing packages.

    Tip
    Tip: Restart the display manager

    YaST makes changes to the display manager settings. You need to log out of your current graphical session and restart the display manager for the changes to take effect.

14.4.1.1 Configuring persistent VNC sessions

After you enable the VNC session management as described in Procedure 14.2, “Enabling persistent VNC sessions”, you can normally connect to the remote session with your favorite VNC viewer, such as vncviewer or Remmina. After you log in, the VNC icon appears in the system tray of your desktop environment. Click the icon to open the VNC Session window. If your desktop environment does not support icons in the system tray, run vncmanager-controller manually.

VNC session settings
Figure 14.8: VNC session settings

There are several settings that influence the VNC session's behavior:

Non-persistent, private

This is equivalent to a one-time session. It is not visible to others and is terminated after you disconnect from it. Refer to Section 14.3, “Configuring one-time sessions on the VNC server” for more information.

Persistent, visible

The session is visible to other users and keeps running even after you disconnect from it.

Session name

Specify the name of the persistent session so that it is easily identified when reconnecting.

No password required

The session is freely accessible without having to log in under user credentials.

Require user login

You need to log in with a valid user name and password to access the session. Lists the valid user names in the Allowed users text box.

Allow one client at a time

Prevents multiple users from joining the session at the same time.

Allow multiple clients at a time

Allows multiple users to join the persistent session at the same time. Useful for remote presentations or training sessions.

Confirm with OK.

14.4.1.2 Joining persistent VNC sessions

After you set up a persistent VNC session as described in Section 14.4.1.1, “Configuring persistent VNC sessions”, you can join it with your VNC viewer. After your VNC client connects to the server, you will be prompted to choose whether you want to create a new session or join the existing one:

Joining a persistent VNC session
Figure 14.9: Joining a persistent VNC session

After you click the name of the existing session, you may be asked for login credentials, depending on the persistent session settings.

14.5 Configuring encryption on the VNC server

If the VNC server is set up properly, all communication between the VNC server and the client is encrypted. The authentication happens at the beginning of the session; the actual data transfer only begins afterward.

Whether for a one-time or a persistent VNC session, security options are configured via the -securitytypes parameter of the /usr/bin/Xvnc command located on the server_args line. The -securitytypes parameter selects both authentication method and encryption. It has the following options:

Authentications
None, TLSNone, x509None

No authentication.

VncAuth, TLSVnc, x509Vnc

Authentication using custom password.

Plain, TLSPlain, x509Plain

Authentication using PAM to verify user's password.

Encryptions
None, vncAuth, plain

No encryption.

TLSNone, TLSVnc, TLSPlain

Anonymous TLS encryption. Everything is encrypted, but there is no verification of the remote host. So you are protected against passive attackers, but not against man-in-the-middle attackers.

X509None, x509Vnc, x509Plain

TLS encryption with certificate. If you use a self-signed certificate, you will be asked to verify it on the first connection. On subsequent connections you will be warned only if the certificate changed. So you are protected against everything except man-in-the-middle on the first connection (similar to typical SSH usage). If you use a certificate signed by a certificate authority matching the machine name, then you get full security (similar to typical HTTPS usage).

Tip
Tip

Some VNC clients refuse to establish a secure connection via the default self-signed certificate. For example, the Vinagre client verifies the certification against the GnuTLS global trust store and fails if the certificate is self-signed. In such a case, either use an encryption method other than x509, or generate a properly signed certificate for the VNC server and import it to the client's system trust store.

Tip
Tip: Path to certificate and key

With X509 based encryption, you need to specify the path to the X509 certificate and the key with -X509Cert and -X509Key options.

If you select multiple security types separated by comma, the first one supported and allowed by both client and server will be used. That way you can configure opportunistic encryption on the server. This is useful if you need to support VNC clients that do not support encryption.

On the client, you can also specify the allowed security types to prevent a downgrade attack if you are connecting to a server which you know has encryption enabled (although our vncviewer will warn you with the "Connection not encrypted!" message in that case).

14.6 Compatibility with Wayland

The Remote Administration (VNC) feature relies on X11 and may result in an empty screen if Wayland is enabled. The display manager must be configured to use X11 instead of Wayland. For gdm, edit /etc/gdm/custom.conf. In the [daemon] section, add WaylandEnable=false to the configuration file. When logging in, the user must choose an X11-compatible session as well. If you wish to remove the Wayland option for GNOME, you can remove and lock the gnome-session-wayland package.

15 File copying with RSync

Today, a typical user has several computers: home and workplace machines, a laptop, a smartphone or a tablet. This makes the task of keeping files and documents in synchronization across multiple devices all the more important.

Warning
Warning: Risk of data loss

Before you start using a synchronization tool, you should familiarize yourself with its features and functionality. Make sure to back up your important files.

15.1 Conceptual overview

For synchronizing a large amount of data over a slow network connection, Rsync offers a reliable method of transmitting only changes within files. This applies not only to text files but also binary files. To detect the differences between files, Rsync subdivides the files into blocks and computes check sums over them.

Detecting changes requires certain computing power. So make sure that machines on both ends have enough resources, including RAM.

Rsync can be particularly useful when large amounts of data containing only minor changes need to be transmitted regularly. This is often the case when working with backups. Rsync can also be useful for mirroring staging servers that store complete directory trees of Web servers to a Web server in a DMZ.

Despite its name, Rsync is not a synchronization tool. Rsync is a tool that copies data only in one direction at a time. It does not and cannot do the reverse. If you need a bidirectional tool which can synchronize both source and destination, use Csync.

15.2 Basic syntax

Rsync is a command-line tool that has the following basic syntax:

rsync [OPTION] SOURCE [SOURCE]... DEST

You can use Rsync on any local or remote machine, provided you have access and write permissions. It is possible to have multiple SOURCE entries. The SOURCE and DEST placeholders can be paths, URLs or both.

Below are the most common Rsync options:

-v

Outputs more verbose text

-a

Archive mode; copies files recursively and preserves time stamps, user/group ownership, file permissions, and symbolic links

-z

Compresses the transmitted data

Note
Note: Trailing slashes count

When working with Rsync, you should pay particular attention to trailing slashes. A trailing slash after the directory denotes the content of the directory. No trailing slash denotes the directory itself.

15.3 Copying files and directories locally

The following description assumes that the current user has write permissions to the directory /var/backup. To copy a single file from one directory on your machine to another path, use the following command:

> rsync -avz backup.tar.xz /var/backup/

The file backup.tar.xz is copied to /var/backup/; the absolute path will be /var/backup/backup.tar.xz.

Do not forget to add the trailing slash after the /var/backup/ directory. If you do not insert the slash, the file backup.tar.xz is copied to /var/backup (file) not inside the directory /var/backup/!

Copying a directory is similar to copying a single file. The following example copies the directory tux/ and its content into the directory /var/backup/:

> rsync -avz tux /var/backup/

Find the copy in the absolute path /var/backup/tux/.

15.4 Copying files and directories remotely

The Rsync tool is required on both machines. To copy files from or to remote directories requires an IP address or a domain name. A user name is optional if your current user names on the local and remote machine are the same.

To copy the file file.tar.xz from your local host to the remote host 192.168.1.1 with same users (being local and remote), use the following command:

> rsync -avz file.tar.xz  tux@192.168.1.1:

Depending on what you prefer, these commands are also possible and equivalent:

> rsync -avz file.tar.xz 192.168.1.1:~
> rsync -avz file.tar.xz 192.168.1.1:/home/tux

In all cases with standard configuration, you will be prompted to enter your passphrase of the remote user. This command will copy file.tar.xz to the home directory of user tux (normally /home/tux).

Copying a directory remotely is similar to copying a directory locally. The following example copies the directory tux/ and its content into the remote directory /var/backup/ on the 192.168.1.1 host:

> rsync -avz tux 192.168.1.1:/var/backup/

Assuming you have write permissions on the host 192.168.1.1, you will find the copy in the absolute path /var/backup/tux.

15.5 Configuring and using an rsync server

Rsync can run as a daemon (rsyncd) listening on default port 873 for incoming connections. This daemon can receive copying targets.

The following description explains how to create an Rsync server on jupiter with a backup target. This target can be used to store your backups. To create an Rsync server, do the following:

Procedure 15.1: Setting up an rsync server
  1. On jupiter, create a directory to store all your backup files. In this example, we use /var/backup:

    # mkdir /var/backup
  2. Specify ownership. In this case, the directory is owned by user tux in group users:

    # chown tux.users /var/backup
  3. Configure the rsyncd daemon.

    We will separate the configuration file into a main file and certain modules which hold your backup target. This makes it easier to add additional targets later. Global values can be stored in /etc/rsyncd.d/*.inc files, whereas your modules are placed in /etc/rsyncd.d/*.conf files:

    1. Create a directory /etc/rsyncd.d/:

      # mkdir /etc/rsyncd.d/
    2. In the main configuration file /etc/rsyncd.conf, add the following lines:

      # rsyncd.conf main configuration file
      log file = /var/log/rsync.log
      pid file = /var/lock/rsync.lock
      
      &merge /etc/rsyncd.d 1
      &include /etc/rsyncd.d 2

      1

      Merges global values from /etc/rsyncd.d/*.inc files into the main configuration file.

      2

      Loads any modules (or targets) from /etc/rsyncd.d/*.conf files. These files should not contain any references to global values.

    3. Create your module (your backup target) in the file /etc/rsyncd.d/backup.conf with the following lines:

      # backup.conf: backup module
      [backup] 1
         uid = tux 2
         gid = users 2
         path = /var/backup 3
         auth users = tux  4
         secrets file = /etc/rsyncd.secrets 5
         comment = Our backup target

      1

      The backup target. You can use any name you like. However, it is a good idea to name a target according to its purpose and use the same name in your *.conf file.

      2

      Specifies the user name or group name that is used when the file transfer takes place.

      3

      Defines the path to store your backups (from Step 1).

      4

      Specifies a comma-separated list of allowed users. In its simplest form, it contains the user names that are allowed to connect to this module. In our case, only user tux is allowed.

      5

      Specifies the path of a file that contains lines with user names and plain passwords.

    4. Create the /etc/rsyncd.secrets file with the following content and replace PASSPHRASE:

      # user:passwd
      tux:PASSPHRASE
    5. Make sure the file is only readable by root:

      # chmod 0600 /etc/rsyncd.secrets
  4. Start and enable the rsyncd daemon with:

    # systemctl enable rsyncd
    # systemctl start rsyncd
  5. Test the access to your Rsync server:

    > rsync jupiter::

    You should see a response that looks like this:

    backup          Our backup target

    Otherwise, check your configuration file, firewall and network settings.

The above steps create an Rsync server that can now be used to store backups. The example also creates a log file listing all connections. This file is stored in /var/log/rsyncd.log. This is useful to debug your transfers.

To list the content of your backup target, use the following command:

> rsync -avz jupiter::backup

This command lists all files present in the directory /var/backup on the server. This request is also logged in the log file /var/log/rsyncd.log. To start an actual transfer, provide a source directory. Use . for the current directory. For example, the following command copies the current directory to your Rsync backup server:

> rsync -avz . jupiter::backup

By default, Rsync does not delete files and directories when it runs. To enable deletion, the additional option --delete must be stated. To ensure that no newer files are deleted, the option --update can be used instead. Any conflicts that arise must be resolved manually.

15.6 More information

Csync

Bidirectional file synchronization tool, see https://csync.org/.

RSnapshot

Creates incremental backups, see https://rsnapshot.org.

Unison

A file synchronization tool similar to CSync but with a graphical interface, see https://www.seas.upenn.edu/~bcpierce/unison/.

Rear

A disaster recovery framework, see the Administration Guide of the SUSE Linux Enterprise High Availability, chapter Disaster Recovery with Rear (Relax-and-Recover).

Part II Booting a Linux system

  • 16 Introduction to the boot process
  • Booting a Linux system involves different components and tasks. After a firmware and hardware initialization process, which depends on the machine's architecture, the kernel is started by means of the boot loader GRUB 2. After this point, the boot process is completely controlled by the operating system and handled by systemd. systemd provides a set of targets that boot configurations for everyday usage, maintenance or emergencies.

  • 17 UEFI (Unified Extensible Firmware Interface)
  • UEFI (Unified Extensible Firmware Interface) is the interface between the firmware that comes with the system hardware, all the hardware components of the system, and the operating system.

  • 18 The boot loader GRUB 2
  • This chapter describes how to configure GRUB 2, the boot loader used in SUSE® Linux Enterprise Server. It is the successor to the traditional GRUB boot loader—now called GRUB Legacy. GRUB 2 has been the default boot loader in SUSE® Linux Enterprise Server since version 12. A YaST module is available for configuring the most important settings. The boot procedure as a whole is outlined in Chapter 16, Introduction to the boot process. For details on Secure Boot support for UEFI machines, see Chapter 17, UEFI (Unified Extensible Firmware Interface).

  • 19 The systemd daemon
  • systemd initializes the system. It has the process ID 1. systemd is started directly by the kernel and resists signal 9, which normally terminates processes. All other programs are started directly by systemd or by one of its child processes. systemd is a replacement for the System V init daemon and…

16 Introduction to the boot process

Booting a Linux system involves different components and tasks. After a firmware and hardware initialization process, which depends on the machine's architecture, the kernel is started by means of the boot loader GRUB 2. After this point, the boot process is completely controlled by the operating system and handled by systemd. systemd provides a set of targets that boot configurations for everyday usage, maintenance or emergencies.

16.1 Terminology

This chapter uses terms that can be interpreted ambiguously. To understand how they are used here, read the definitions below:

init

Two different processes are commonly named init:

  • The initramfs process mounting the root file system

  • The operating system process that starts all other processes that is executed from the real root file system

In both cases, the systemd program is taking care of this task. It is first executed from the initramfs to mount the root file system. When that has succeeded, it is re-executed from the root file system as the initial process. To avoid confusing these two systemd processes, we refer to the first process as init on initramfs and to the second one as systemd.

initrd/initramfs

An initrd (initial RAM disk) is an image file containing a root file system image which is loaded by the kernel and mounted from /dev/ram as the temporary root file system. Mounting this file system requires a file system driver.

Beginning with kernel 2.6.13, the initrd has been replaced by the initramfs (initial RAM file system), which does not require a file system driver to be mounted. SUSE Linux Enterprise Server exclusively uses an initramfs. However, since the initramfs is stored as /boot/initrd, it is often called initrd. In this chapter we exclusively use the name initramfs.

16.2 The Linux boot process

The Linux boot process consists of several stages, each represented by a different component:

16.2.1 The initialization and boot loader phase

During the initialization phase the machine's hardware is set up and the devices are prepared. This process differs significantly between hardware architectures.

SUSE Linux Enterprise Server uses the boot loader GRUB 2 on all architectures. Depending on the architecture and firmware, starting the GRUB 2 boot loader can be a multi-step process. The purpose of the boot loader is to load the kernel and the initial, RAM-based file system (initramfs). For more information about GRUB 2, refer to Chapter 18, The boot loader GRUB 2.

16.2.1.1 Initialization and boot loader phase on AArch64 and AMD64/Intel 64

After turning on the computer, the BIOS or the UEFI initializes the screen and keyboard, and tests the main memory. Up to this stage, the machine does not access any mass storage media. Subsequently, the information about the current date, time, and the most important peripherals are loaded from the CMOS values. When the boot media and its geometry are recognized, the system control passes from the BIOS/UEFI to the boot loader.

On a machine equipped with a traditional BIOS, only code from the first physical 512-byte data sector (the Master Boot Record, MBR) of the boot disk can be loaded. Only a minimal GRUB 2 fits into the MBR. Its sole purpose is to load a GRUB 2 core image containing file system drivers from the gap between the MBR and the first partition (MBR partition table) or from the BIOS boot partition (GPT partition table). This image contains file system drivers and therefore is able to access /boot located on the root file system. /boot contains additional modules for GRUB 2 core as well as the kernel and the initramfs image. When it has access to this partition, GRUB 2 loads the kernel and the initramfs image into memory and hands control over to the kernel.

When booting a BIOS system from an encrypted file system that includes an encrypted /boot partition, you need to enter the password for decryption twice. It is first needed by GRUB 2 to decrypt /boot and then for systemd to mount the encrypted volumes.

On machines with UEFI the boot process is much simpler than on machines with a traditional BIOS. The firmware is able to read from a FAT formatted system partition of disks with a GPT partition table. This EFI system-partition (in the running system mounted as /boot/efi) holds enough space to host a fully-fledged GRUB 2 which is directly loaded and executed by the firmware.

If the BIOS/UEFI supports network booting, it is also possible to configure a boot server that provides the boot loader. The system can then be booted via PXE. The BIOS/UEFI acts as the boot loader. It gets the boot image from the boot server and starts the system. This is completely independent of local hard disks.

16.2.1.2 Initialization and boot loader phase on IBM Z

On IBM Z the boot process must be initialized by a boot loader called zipl (z initial program load). Although zipl supports reading from various file systems, it does not support the SLE default file system (Btrfs) or booting from snapshots. SUSE Linux Enterprise Server therefore uses a two-stage boot process that ensures full Btrfs support at boot-time:

  1. zipl boots from the partition /boot/zipl, which can be formatted with the Ext2, Ext3, Ext4, or XFS file system. This partition contains a minimal kernel and an initramfs that are loaded into memory. The initramfs contains a Btrfs driver (among others) and the boot loader GRUB 2. The kernel is started with a parameter initgrub, which tells it to start GRUB 2.

  2. The kernel mounts the root file system, so /boot becomes accessible. Now GRUB 2 is started from the initramfs. It reads its configuration from /boot/grub2/grub.cfg and loads the final kernel and initramfs from /boot. The new kernel now gets loaded via Kexec.

16.2.2 The kernel phase

When the boot loader has passed on system control, the boot process is the same on all architectures. The boot loader loads both the kernel and an initial RAM-based file system (initramfs) into memory and the kernel takes over.

After the kernel has set up memory management and has detected the CPU type and its features, it initializes the hardware and mounts the temporary root file system from the memory that was loaded with the initramfs.

16.2.2.1 The initramfs file

initramfs (initial RAM file system) is a small cpio archive that the kernel can load into a RAM disk. It is located at /boot/initrd. It can be created with a tool called dracut—refer to man 8 dracut for details.

The initramfs provides a minimal Linux environment that enables the execution of programs before the actual root file system is mounted. This minimal Linux environment is loaded into memory by BIOS or UEFI routines and does not have specific hardware requirements other than sufficient memory. The initramfs archive must always provide an executable named init that executes the systemd daemon on the root file system for the boot process to proceed.

Before the root file system can be mounted and the operating system can be started, the kernel needs the corresponding drivers to access the device on which the root file system is located. These drivers may include special drivers for certain kinds of hard disks or even network drivers to access a network file system. The needed modules for the root file system are loaded by init on initramfs. After the modules are loaded, udev provides the initramfs with the needed devices. Later in the boot process, after changing the root file system, it is necessary to regenerate the devices. This is done by the systemd unit systemd-udev-trigger.service.

16.2.2.1.1 Regenerating the initramfs

Because the initramfs contains drivers, it needs to be updated whenever a new version of one of its drivers is available. This is done automatically when installing the package containing the driver update. YaST or zypper will inform you about this by showing the output of the command that generates the initramfs. However, there are some occasions when you need to regenerate an initramfs manually:

Adding drivers because of hardware changes

If you need to change hardware (for example, hard disks), and this hardware requires different drivers to be in the kernel at boot time, you must update the initramfs file.

Open or create /etc/dracut.conf.d/10-DRIVER.conf and add the following line (mind the leading blank space):

force_drivers+=" DRIVER1 "

Replace DRIVER1 with the module name of the driver. If you need to add more than one driver, list them space-separated:

force_drivers+=" DRIVER1 DRIVER2 "

Proceed with Procedure 16.1, “Generate an initramfs”.

Moving system directories to a RAID or LVM

Whenever you move swap files, or system directories like /usr in a running system to a RAID or logical volume, you need to create an initramfs that contains support for software RAID or LVM drivers.

To do so, create the respective entries in /etc/fstab and mount the new entries (for example with mount -a and/or swapon -a).

Proceed with Procedure 16.1, “Generate an initramfs”.

Adding disks to an LVM group or Btrfs RAID containing the root file system

Whenever you add (or remove) a disk to a logical volume group or a Btrfs RAID containing the root file system, you need to create an initramfs that contains support for the enlarged volume. Follow the instructions at Procedure 16.1, “Generate an initramfs”.

Proceed with Procedure 16.1, “Generate an initramfs”.

Changing kernel variables

If you change the values of kernel variables via the sysctl interface by editing related files (/etc/sysctl.conf or /etc/sysctl.d/*.conf), the change will be lost on the next system reboot. Even if you load the values with sysctl --system at runtime, the changes are not saved into the initramfs file. You need to update it by proceeding as outlined in Procedure 16.1, “Generate an initramfs”.

Procedure 16.1: Generate an initramfs

Note that all commands in the following procedure need to be executed as the root user.

  1. Enter your /boot directory:

    # cd /boot
  2. Generate a new initramfs file with dracut, replacing MY_INITRAMFS with a file name of your choice:

    # dracut MY_INITRAMFS

    Alternatively, run dracut -f FILENAME to replace an existing init file.

  3. (Skip this step if you ran dracut -f in the previous step.) Create a symbolic link from the initramfs file you created in the previous step to initrd:

    #  ln -sf MY_INITRAMFS initrd
  4. On the IBM Z architecture, additionally run grub2-install.

16.2.3 The init on initramfs phase

The temporary root file system mounted by the kernel from the initramfs contains the executable systemd (which is called init on initramfs in the following, also see Section 16.1, “Terminology”. This program performs all actions needed to mount the proper root file system. It provides kernel functionality for the needed file system and device drivers for mass storage controllers with udev.

The main purpose of init on initramfs is to prepare the mounting of and access to the real root file system. Depending on your system configuration, init on initramfs is responsible for the following tasks.

Loading kernel modules

Depending on your hardware configuration, special drivers may be needed to access the hardware components of your computer (the most important component being your hard disk). To access the final root file system, the kernel needs to load the proper file system drivers.

Providing block special files

The kernel generates device events depending on loaded modules. udev handles these events and generates the required special block files on a RAM file system in /dev. Without those special files, the file system and other devices would not be accessible.

Managing RAID and LVM setups

If you configured your system to hold the root file system under RAID or LVM, init on initramfs sets up LVM or RAID to enable access to the root file system later.

Managing the network configuration

If you configured your system to use a network-mounted root file system (mounted via NFS), init must make sure that the proper network drivers are loaded and that they are set up to allow access to the root file system.

If the file system resides on a network block device like iSCSI or SAN, the connection to the storage server is also set up by init on initramfs. SUSE Linux Enterprise Server supports booting from a secondary iSCSI target if the primary target is not available. For more details regarding configuration of the booting iSCSI target refer to Book “Storage Administration Guide”, Chapter 15 “Mass storage over IP networks: iSCSI”, Section 15.3.1 “Using YaST for the iSCSI initiator configuration”.

Note
Note: Handling of mount failures

If the root file system fails to mount from within the boot environment, it must be checked and repaired before the boot can continue. The file system checker will be automatically started for Ext3 and Ext4 file systems. The repair process is not automated for XFS and Btrfs file systems, and the user is presented with information describing the options available to repair the file system. When the file system has been successfully repaired, exiting the boot environment will cause the system to retry mounting the root file system. If successful, the boot will continue normally.

16.2.3.1 The init on initramfs phase in the installation process

When init on initramfs is called during the initial boot as part of the installation process, its tasks differ from those mentioned above. Note that the installation system also does not start systemd from initramfs—these tasks are performed by linuxrc.

Finding the installation medium

When starting the installation process, your machine loads an installation kernel and a special init containing the YaST installer. The YaST installer is running in a RAM file system and needs to have information about the location of the installation medium to access it for installing the operating system.

Initiating hardware recognition and loading appropriate kernel modules

As mentioned in Section 16.2.2.1, “The initramfs file”, the boot process starts with a minimum set of drivers that can be used with most hardware configurations. On AArch64, POWER, and AMD64/Intel 64 machines, linuxrc starts an initial hardware scanning process that determines the set of drivers suitable for your hardware configuration. On IBM Z, a list of drivers and their parameters needs to be provided, for example via linuxrc or a parmfile.

These drivers are used to generate a custom initramfs that is needed to boot the system. If the modules are not needed for boot but for coldplug, the modules can be loaded with systemd; for more information, see Section 19.6.4, “Loading kernel modules”.

Loading the installation system

When the hardware is properly recognized, the appropriate drivers are loaded. The udev program creates the special device files and linuxrc starts the installation system with the YaST installer.

Starting YaST

Finally, linuxrc starts YaST, which starts the package installation and the system configuration.

16.2.4 The systemd phase

After the real root file system has been found, it is checked for errors and mounted. If this is successful, the initramfs is cleaned and the systemd daemon on the root file system is executed. systemd is Linux's system and service manager. It is the parent process that is started as PID 1 and acts as an init system which brings up and maintains user space services. See Chapter 19, The systemd daemon for details.

17 UEFI (Unified Extensible Firmware Interface)

UEFI (Unified Extensible Firmware Interface) is the interface between the firmware that comes with the system hardware, all the hardware components of the system, and the operating system.

UEFI is becoming more and more available on PC systems and thus is replacing the traditional PC-BIOS. UEFI, for example, properly supports 64-bit systems and offers secure booting (Secure Boot, firmware version 2.3.1c or better required), which is one of its most important features. Lastly, with UEFI a standard firmware will become available on all x86 platforms.

UEFI additionally offers the following advantages:

  • Booting from large disks (over 2 TiB) with a GUID Partition Table (GPT).

  • CPU-independent architecture and drivers.

  • Flexible pre-OS environment with network capabilities.

  • CSM (Compatibility Support Module) to support booting legacy operating systems via a PC-BIOS-like emulation.

For more information, see https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface. The following sections are not meant as a general UEFI overview; these are only hints about how certain features are implemented in SUSE Linux Enterprise Server.

17.1 Secure boot

In the world of UEFI, securing the bootstrapping process means establishing a chain of trust. The platform is the root of this chain of trust; in the context of SUSE Linux Enterprise Server, the mainboard and the on-board firmware could be considered the platform. In other words, it is the hardware vendor, and the chain of trust flows from that hardware vendor to the component manufacturers, the OS vendors, etc.

The trust is expressed via public key cryptography. The hardware vendor puts a so-called Platform Key (PK) into the firmware, representing the root of trust. The trust relationship with operating system vendors and others is documented by signing their keys with the Platform Key.

Finally, security is established by requiring that no code will be executed by the firmware unless it has been signed by one of these trusted keys—be it an OS boot loader, a driver located in the flash memory of certain PCI Express card or on disk, or be it an update of the firmware itself.

To use Secure Boot, you need to have your OS loader signed with a key trusted by the firmware, and you need the OS loader to verify that the kernel it loads can be trusted.

Key Exchange Keys (KEK) can be added to the UEFI key database. This way, you can use other certificates, if they are signed with the private part of the PK.

17.1.1 Implementation on SUSE Linux Enterprise Server

Microsoft’s Key Exchange Key (KEK) is installed by default.

Note
Note: GUID partitioning table (GPT) required

The Secure Boot feature is enabled by default on UEFI/x86_64 installations. You can find the Enable Secure Boot Support option in the Boot Code Options tab of the Boot Loader Settings dialog. It supports booting when the secure boot is activated in the firmware, while making it possible to boot when it is deactivated.

Secure boot support
Figure 17.1: Secure boot support

The Secure Boot feature requires that a GUID Partitioning Table (GPT) replaces the old partitioning with a Master Boot Record (MBR). If YaST detects EFI mode during the installation, it will try to create a GPT partition. UEFI expects to find the EFI programs on a FAT-formatted EFI System Partition (ESP).

Supporting UEFI Secure Boot requires having a boot loader with a digital signature that the firmware recognizes as a trusted key. That key is trusted by the firmware a priori, without requiring any manual intervention.

There are two ways of getting there. One is to work with hardware vendors to have them endorse a SUSE key, which SUSE then signs the boot loader with. The other way is to go through Microsoft’s Windows Logo Certification program to have the boot loader certified and have Microsoft recognize the SUSE signing key (that is, have it signed with their KEK). By now, SUSE got the loader signed by UEFI Signing Service (that is Microsoft in this case).

UEFI: secure boot process
Figure 17.2: UEFI: secure boot process

At the implementation layer, SUSE uses the shim loader which is installed by default. It is a smart solution that avoids legal issues, and simplifies the certification and signing step considerably. The shim loader’s job is to load a boot loader such as GRUB 2 and verify it; this boot loader in turn will load kernels signed by a SUSE key only.

There are two types of trusted users:

  • First, those who hold the keys. The Platform Key (PK) allows almost everything. The Key Exchange Key (KEK) allows all a PK can except changing the PK.

  • Second, anyone with physical access to the machine. A user with physical access can reboot the machine, and configure UEFI.

UEFI offers two types of variables to fulfill the needs of those users:

  • The first is the so-called Authenticated Variables, which can be updated from both within the boot process (the so-called Boot Services Environment) and the running OS. This can be done only when the new value of the variable is signed with the same key that the old value of the variable was signed with. And they can only be appended to or changed to a value with a higher serial number.

  • The second is the so-called Boot Services Only Variables. These variables are accessible to any code that runs during the boot process. After the boot process ends and before the OS starts, the boot loader must call the ExitBootServices call. After that, these variables are no longer accessible, and the OS cannot touch them.

UEFI key lists are of the first type, as this allows online updating, adding and blacklisting of keys, drivers and firmware fingerprints. It is the second type of variable, the Boot Services Only Variable, that helps to implement Secure Boot in a secure and open source-friendly manner, and thus compatible with GPLv3.

SUSE starts with shim—a small and simple EFI boot loader signed by SUSE and Microsoft.

This allows shim to load and execute.

shim then goes on to verify that the boot loader it wants to load is trusted. In a default situation shim will use an independent SUSE certificate embedded in its body. In addition, shim will allow to enroll additional keys, overriding the default SUSE key. In the following, we call them Machine Owner Keys or MOKs for short.

Next the boot loader will verify and then boot the kernel, and the kernel will do the same on the modules.

17.1.2 MOK (Machine Owner Key)

To replace specific kernels, drivers or other components that are part of the boot process, you need to use Machine Owner Keys (MOKs). The mokutil tool can help you to manage MOKs.

You can create a MOK enrollment request with mokutil. The request is stored in a UEFI runtime (RT) variable called MokNew. During the next boot, the shim boot loader detects MokNew and loads MokManager, which presents you with several options. You can use the Enroll key from disk and Enroll hash from disk options to add the key to the MokList. Use the Enroll MOK option to copy the key from the MokNew variable.

Enrolling a key from disk is normally done when the shim fails to load grub2 and falls back to loading MokManager. As MokNew does not exist yet, you have the option of locating the key on the UEFI partition.

17.1.3 Booting a custom kernel

The following is based on https://en.opensuse.org/openSUSE:UEFI#Booting_a_custom_kernel.

Secure Boot does not prevent you from using a self-compiled kernel. You must sign it with your own certificate and make that certificate known to the firmware or MOK.

  1. Create a custom X.509 key and certificate used for signing:

    openssl req -new -x509 -newkey rsa:2048 -keyout key.asc \
      -out cert.pem -nodes -days 666 -subj "/CN=$USER/"

    For more information about creating certificates, see https://en.opensuse.org/openSUSE:UEFI_Image_File_Sign_Tools#Create_Your_Own_Certificate.

  2. Package the key and the certificate as a PKCS#12 structure:

    > openssl pkcs12 -export -inkey key.asc -in cert.pem \
      -name kernel_cert -out cert.p12
  3. Generate an NSS database for use with pesign:

    > certutil -d . -N
  4. Import the key and the certificate contained in PKCS#12 into the NSS database:

    > pk12util -d . -i cert.p12
  5. Bless the kernel with the new signature using pesign:

    > pesign -n . -c kernel_cert -i arch/x86/boot/bzImage \
      -o vmlinuz.signed -s
  6. List the signatures on the kernel image:

    > pesign -n . -S -i vmlinuz.signed

    At that point, you can install the kernel in /boot as usual. Because the kernel now has a custom signature the certificate used for signing needs to be imported into the UEFI firmware or MOK.

  7. Convert the certificate to the DER format for import into the firmware or MOK:

    > openssl x509 -in cert.pem -outform der -out cert.der
  8. Copy the certificate to the ESP for easier access:

    > sudo cp cert.der /boot/efi/
  9. Use mokutil to launch the MOK list automatically.

      1. Import the certificate to MOK:

        > mokutil --root-pw --import cert.der

        The --root-pw option enables usage of the root user directly.

      2. Check the list of certificates that are prepared to be enrolled:

        > mokutil --list-new
      3. Reboot the system; shim should launch MokManager. You need to enter the root password to confirm the import of the certificate to the MOK list.

      4. Check if the newly imported key was enrolled:

        > mokutil --list-enrolled
      1. Alternatively, this is the procedure to launch MOK manually:

        Reboot

      2. In the GRUB 2 menu press the 'c' key.

      3. Type:

        chainloader $efibootdir/MokManager.efi
        boot
      4. Select Enroll key from disk.

      5. Navigate to the cert.der file and press Enter.

      6. Follow the instructions to enroll the key. Normally this should be pressing '0' and then 'y' to confirm.

        Alternatively, the firmware menu may provide ways to add a new key to the Signature Database.

17.1.4 Using non-inbox drivers

There is no support for adding non-inbox drivers (that is, drivers that do not come with SUSE Linux Enterprise Server) during installation with Secure Boot enabled. The signing key used for SolidDriver/PLDP is not trusted by default.

It is possible to install third party drivers during installation with Secure Boot enabled in two different ways. In both cases:

  • Add the needed keys to the firmware database via firmware/system management tools before the installation. This option depends on the specific hardware you are using. Consult your hardware vendor for more information.

  • Use a bootable driver ISO from https://drivers.suse.com/ or your hardware vendor to enroll the needed keys in the MOK list at first boot.

To use the bootable driver ISO to enroll the driver keys to the MOK list, follow these steps:

  1. Burn the ISO image above to an empty CD/DVD medium.

  2. Start the installation using the new CD/DVD medium, having the standard installation media at hand or a URL to a network installation server.

    If doing a network installation, enter the URL of the network installation source on the boot command line using the install= option.

    If doing installation from optical media, the installer will first boot from the driver kit and then ask to insert the first installation disk of the product.

  3. An initrd containing updated drivers will be used for installation.

For more information, see https://drivers.suse.com/doc/Usage/Secure_Boot_Certificate.html.

17.1.5 Features and limitations

When booting in Secure Boot mode, the following features apply:

  • Installation to UEFI default boot loader location, a mechanism to keep or restore the EFI boot entry.

  • Reboot via UEFI.

  • Xen hypervisor will boot with UEFI when there is no legacy BIOS to fall back to.

  • UEFI IPv6 PXE boot support.

  • UEFI video mode support, the kernel can retrieve video mode from UEFI to configure KMS mode with the same parameters.

  • UEFI booting from USB devices is supported.

  • Since SUSE Linux Enterprise Server 15 SP3, Kexec and Kdump are supported in Secure Boot mode.

When booting in Secure Boot mode, the following limitations apply:

  • To ensure that Secure Boot cannot be easily circumvented, certain kernel features are disabled when running under Secure Boot.

  • Boot loader, kernel, and kernel modules must be signed.

  • Hibernation (suspend on disk) is disabled.

  • Access to /dev/kmem and /dev/mem is not possible, not even as root user.

  • Access to the I/O port is not possible, not even as root user. All X11 graphical drivers must use a kernel driver.

  • PCI BAR access through sysfs is not possible.

  • custom_method in ACPI is not available.

  • debugfs for asus-wmi module is not available.

  • the acpi_rsdp parameter does not have any effect on the kernel.

17.2 More information

18 The boot loader GRUB 2

This chapter describes how to configure GRUB 2, the boot loader used in SUSE® Linux Enterprise Server. It is the successor to the traditional GRUB boot loader—now called GRUB Legacy. GRUB 2 has been the default boot loader in SUSE® Linux Enterprise Server since version 12. A YaST module is available for configuring the most important settings. The boot procedure as a whole is outlined in Chapter 16, Introduction to the boot process. For details on Secure Boot support for UEFI machines, see Chapter 17, UEFI (Unified Extensible Firmware Interface).

18.1 Main differences between GRUB legacy and GRUB 2

  • The configuration is stored in different files.

  • More file systems are supported (for example, Btrfs).

  • Can directly read files stored on LVM or RAID devices.

  • The user interface can be translated and altered with themes.

  • Includes a mechanism for loading modules to support additional features, such as file systems, etc.

  • Automatically searches for and generates boot entries for other kernels and operating systems, such as Windows.

  • Includes a minimal Bash-like console.

18.2 Configuration file structure

The configuration of GRUB 2 is based on the following files:

/boot/grub2/grub.cfg

This file contains the configuration of the GRUB 2 menu items. It replaces menu.lst used in GRUB Legacy. grub.cfg should not be edited—it is automatically generated by the command grub2-mkconfig -o /boot/grub2/grub.cfg.

/boot/grub2/custom.cfg

This optional file is directly sourced by grub.cfg at boot time and can be used to add custom items to the boot menu. Starting with SUSE Linux Enterprise Server 12 SP2 these entries are also parsed when using grub-once.

/etc/default/grub

This file controls the user settings of GRUB 2 and normally includes additional environmental settings such as backgrounds and themes.

Scripts under /etc/grub.d/

The scripts in this directory are read during execution of the command grub2-mkconfig -o /boot/grub2/grub.cfg. Their instructions are integrated into the main configuration file /boot/grub/grub.cfg.

/etc/sysconfig/bootloader

This configuration file holds certain basic settings like the boot loader type and whether to enable UEFI Secure Boot support.

/boot/grub2/x86_64-efi, /boot/grub2/power-ieee1275, /boot/grub2/s390x

These configuration files contain architecture-specific options.

GRUB 2 can be controlled in multiple ways. Boot entries from an existing configuration can be selected from the graphical menu (splash screen). The configuration is loaded from the file /boot/grub2/grub.cfg which is compiled from other configuration files (see below). All GRUB 2 configuration files are considered system files, and you need root privileges to edit them.

Note
Note: Activating configuration changes

After having manually edited GRUB 2 configuration files, you need to run grub2-mkconfig -o /boot/grub2/grub.cfg to activate the changes. However, this is not necessary when changing the configuration with YaST, because YaST automatically runs this command.

18.2.1 The file /boot/grub2/grub.cfg

The graphical splash screen with the boot menu is based on the GRUB 2 configuration file /boot/grub2/grub.cfg, which contains information about all partitions or operating systems that can be booted by the menu.

Every time the system is booted, GRUB 2 loads the menu file directly from the file system. For this reason, GRUB 2 does not need to be re-installed after changes to the configuration file. grub.cfg is automatically rebuilt with kernel installations or removals.

grub.cfg is compiled from the file /etc/default/grub and scripts found in the /etc/grub.d/ directory when running the command grub2-mkconfig -o /boot/grub2/grub.cfg. Therefore you should never edit the file manually. Instead, edit the related source files or use the YaST Boot Loader module to modify the configuration as described in Section 18.3, “Configuring the boot loader with YaST”.

18.2.2 The file /etc/default/grub

More general options of GRUB 2 belong in this file, such as the time the menu is displayed, or the default OS to boot. To list all available options, see the output of the following command:

> grep "export GRUB_DEFAULT" -A50 /usr/sbin/grub2-mkconfig | grep GRUB_

You can introduce custom variables and use them later in the scripts found in the /etc/grub.d directory.

After having edited /etc/default/grub, update the main configuration file with grub2-mkconfig -o /boot/grub2/grub.cfg.

Note
Note: Scope

All options specified in this file are general options that affect all boot entries. Options specific to a Xen hypervisor include the _XEN_ substring.

Important
Important: Escaping inner quotes

More complex options with spaces require quoting so that they are processed as one option. Such inner quotes need to be correctly escaped, for example:

GRUB_CMDLINE_LINUX_XEN="debug loglevel=9 log_buf_len=5M \"ddebug_query=file drivers/xen/xen-acpi-processor.c +p\""
GRUB_DEFAULT

Sets the boot menu entry that is booted by default. Its value can be a numeric value, the complete name of a menu entry, or saved.

GRUB_DEFAULT=2 boots the third (counted from zero) boot menu entry.

GRUB_DEFAULT="2>0" boots the first submenu entry of the third top-level menu entry.

GRUB_DEFAULT="Example boot menu entry" boots the menu entry with the title Example boot menu entry.

GRUB_DEFAULT=saved boots the entry specified by the grub2-once or grub2-set-default commands. While grub2-reboot sets the default boot entry for the next reboot only, grub2-set-default sets the default boot entry until changed. grub2-editenv list lists the next boot entry.

GRUB_HIDDEN_TIMEOUT

Waits the specified number of seconds for the user to press a key. During the period no menu is shown unless the user presses a key. If no key is pressed during the time specified, the control is passed to GRUB_TIMEOUT. GRUB_HIDDEN_TIMEOUT=0 first checks whether Shift is pressed and shows the boot menu if yes, otherwise immediately boots the default menu entry. This is the default when only one bootable OS is identified by GRUB 2.

GRUB_HIDDEN_TIMEOUT_QUIET

If false is specified, a countdown timer is displayed on a blank screen when the GRUB_HIDDEN_TIMEOUT feature is active.

GRUB_TIMEOUT

Time period in seconds the boot menu is displayed before automatically booting the default boot entry. If you press a key, the timeout is cancelled and GRUB 2 waits for you to make the selection manually. GRUB_TIMEOUT=-1 causes the menu to be displayed until you select the boot entry manually.

GRUB_CMDLINE_LINUX

Entries on this line are added at the end of the boot entries for normal and recovery modes. Use it to add kernel parameters to the boot entry.

GRUB_CMDLINE_LINUX_DEFAULT

Same as GRUB_CMDLINE_LINUX but the entries are appended in the normal mode only.

GRUB_CMDLINE_LINUX_RECOVERY

Same as GRUB_CMDLINE_LINUX but the entries are appended in the recovery mode only.

GRUB_CMDLINE_LINUX_XEN_REPLACE

This entry replaces the GRUB_CMDLINE_LINUX parameters for all Xen boot entries.

GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT

Same as GRUB_CMDLINE_LINUX_XEN_REPLACE but it only replaces parameters of GRUB_CMDLINE_LINUX_DEFAULT.

GRUB_CMDLINE_XEN

These entries are passed to the Xen hypervisor Xen menu entries for normal and recovery modes. For example:

GRUB_CMDLINE_XEN="loglvl=all guest_loglvl=all"
Tip
Tip: Xen hypervisor options

Find a complete list of Xen hypervisor options in https://xenbits.xen.org/docs/unstable/misc/xen-command-line.html

GRUB_CMDLINE_XEN_DEFAULT

Same as GRUB_CMDLINE_XEN but the entries are appended in the normal mode only.

GRUB_TERMINAL

Enables and specifies an input/output terminal device. Can be console (PC BIOS and EFI consoles), serial (serial terminal), ofconsole (Open Firmware console), or the default gfxterm (graphics-mode output). It is also possible to enable more than one device by quoting the required options, for example, GRUB_TERMINAL="console serial".

GRUB_GFXMODE

The resolution used for the gfxterm graphical terminal. You can only use modes supported by your graphics card (VBE). The default is ‘auto’, which tries to select a preferred resolution. You can display the screen resolutions available to GRUB 2 by typing videoinfo in the GRUB 2 command line. The command line is accessed by typing C when the GRUB 2 boot menu screen is displayed.

You can also specify a color depth by appending it to the resolution setting, for example, GRUB_GFXMODE=1280x1024x24.

GRUB_BACKGROUND

Set a background image for the gfxterm graphical terminal. The image must be a file readable by GRUB 2 at boot time, and it must end with the .png, .tga, .jpg, or .jpeg suffix. If necessary, the image is scaled to fit the screen.

GRUB_DISABLE_OS_PROBER

If this option is set to true, automatic searching for other operating systems is disabled. Only the kernel images in /boot/ and the options from your own scripts in /etc/grub.d/ are detected.

SUSE_BTRFS_SNAPSHOT_BOOTING

If this option is set to true, GRUB 2 can boot directly into Snapper snapshots. For more information, see Section 10.3, “System rollback by booting from snapshots”.

For a complete list of options, see the GNU GRUB manual.

18.2.3 Scripts in /etc/grub.d

The scripts in this directory are read during execution of the command grub2-mkconfig -o /boot/grub2/grub.cfg. Their instructions are incorporated into /boot/grub2/grub.cfg. The order of menu items in grub.cfg is determined by the order in which the files in this directory are run. Files with a leading numeral are executed first, beginning with the lowest number. 00_header is run before 10_linux, which would run before 40_custom. If files with alphabetic names are present, they are executed after the numerically named files. Only executable files generate output to grub.cfg during execution of grub2-mkconfig. By default all files in the /etc/grub.d directory are executable.

Tip
Tip: Persistent custom content in grub.cfg

Because /boot/grub2/grub.cfg is recompiled each time grub2-mkconfig is run, any custom content is lost. To insert your lines directly into /boot/grub2/grub.cfg without losing them after grub2-mkconfig is run, insert them between

### BEGIN /etc/grub.d/90_persistent ###

and

### END /etc/grub.d/90_persistent ###

The 90_persistent script ensures that such content is preserved.

A list of the most important scripts follows:

00_header

Sets environmental variables such as system file locations, display settings, themes and previously saved entries. It also imports preferences stored in the /etc/default/grub. Normally you do not need to make changes to this file.

10_linux

Identifies Linux kernels on the root device and creates relevant menu entries. This includes the associated recovery mode option if enabled. Only the latest kernel is displayed on the main menu page, with additional kernels included in a submenu.

30_os-prober

This script uses os-prober to search for Linux and other operating systems and places the results in the GRUB 2 menu. There are sections to identify specific other operating systems, such as Windows or macOS.

40_custom

This file provides a simple way to include custom boot entries into grub.cfg. Make sure that you do not change the exec tail -n +3 $0 part at the beginning.

The processing sequence is set by the preceding numbers with the lowest number being executed first. If scripts are preceded by the same number the alphabetical order of the complete name decides the order.

Tip
Tip: /boot/grub2/custom.cfg

If you create /boot/grub2/custom.cfg and fill it with content, it is automatically included into /boot/grub2/grub.cfg right after 40_custom at boot time.

18.2.4 Mapping between BIOS drives and Linux devices

In GRUB Legacy, the device.map configuration file was used to derive Linux device names from BIOS drive numbers. The mapping between BIOS drives and Linux devices cannot always be guessed correctly. For example, GRUB Legacy would get a wrong order if the boot sequence of IDE and SCSI drives is exchanged in the BIOS configuration.

GRUB 2 avoids this problem by using device ID strings (UUIDs) or file system labels when generating grub.cfg. GRUB 2 utilities create a temporary device map on the fly, which is normally sufficient, particularly for single-disk systems.

However, if you need to override the GRUB 2's automatic device mapping mechanism, create your custom mapping file /boot/grub2/device.map. The following example changes the mapping to make DISK 3 the boot disk. GRUB 2 partition numbers start with 1 and not with 0 as in GRUB 2 Legacy.

(hd1)  /dev/disk-by-id/DISK3 ID
(hd2)  /dev/disk-by-id/DISK1 ID
(hd3)  /dev/disk-by-id/DISK2 ID

18.2.5 Editing menu entries during the boot procedure

Being able to directly edit menu entries is useful when the system does not boot anymore because of a faulty configuration. It can also be used to test new settings without altering the system configuration.

  1. In the graphical boot menu, select the entry you want to edit with the arrow keys.

  2. Press E to open the text-based editor.

  3. Use the arrow keys to move to the line you want to edit.

    GRUB 2 boot editor
    Figure 18.1: GRUB 2 boot editor

    Now you have two options:

    1. Add space-separated parameters to the end of the line starting with linux or linuxefi to edit the kernel parameters. A complete list of parameters is available at https://en.opensuse.org/Linuxrc.

    2. Or edit the general options to change, for example, the kernel version. The →| key suggests all possible completions.

  4. Press F10 to boot the system with the changes you made or press Esc to discard your edits and return to the GRUB 2 menu.

Changes made this way only apply to the current boot process and are not saved permanently.

Important
Important: Keyboard layout during the boot procedure

The US keyboard layout is the only one available when booting. See Book “Deployment Guide”, Chapter 12 “Troubleshooting”, Section 12.3 “Booting from installation media fails”, US keyboard layout.

Note
Note: Boot loader on the installation media

The Boot Loader of the installation media on systems with a traditional BIOS is still GRUB Legacy. To add boot parameters, select an entry and start typing. Additions you make to the installation boot entry are permanently saved in the installed system.

Note
Note: Editing GRUB 2 menu entries on IBM Z

Cursor movement and editing commands on IBM Z differ—see Section 18.4, “Differences in terminal usage on IBM Z” for details.

18.2.6 Setting a boot password

Even before the operating system is booted, GRUB 2 enables access to file systems. Users without root permissions can access files in your Linux system to which they have no access after the system is booted. To block this kind of access or to prevent users from booting certain menu entries, set a boot password.

Important
Important: Booting requires a password

If set, the boot password is required on every boot, which means the system does not boot automatically.

Proceed as follows to set a boot password. Alternatively use YaST (Protect Boot Loader with Password ).

  1. Encrypt the password using grub2-mkpasswd-pbkdf2:

    > sudo grub2-mkpasswd-pbkdf2
    Password: ****
    Reenter password: ****
    PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...
  2. Paste the resulting string into the file /etc/grub.d/40_custom together with the set superusers command.

    set superusers="root"
    password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...
  3. To import the changes into the main configuration file, run:

    > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

After you reboot, GRUB 2 prompts you for a user name and a password when trying to boot a menu entry. Enter root and the password you typed during the grub2-mkpasswd-pbkdf2 command. If the credentials are correct, the system boots the selected boot entry.

For more information, see https://www.gnu.org/software/grub/manual/grub.html#Security.

18.2.7 Authorized access to boot menu entries

You can configure GRUB 2 to allow access to boot menu entries depending on the level of authorization. You can configure multiple user accounts protected with passwords and assign them access to different menu entries. To configure authorization in GRUB 2, follow these steps:

  1. Create and encrypt one password for each user account you want to use in GRUB 2. Use the grub2-mkpasswd-pbkdf2 command as described in Section 18.2.6, “Setting a boot password”.

  2. Delete the file /etc/grub.d/10_linux. This prevents outputting the default GRUB 2 menu entries.

  3. Edit the /boot/grub2/custom.cfg file and add custom menu entries manually. The following template is an example, adjust it to better match your use case:

    set superusers=admin
    password admin ADMIN_PASSWORD
    password maintainer MAINTAINER_PASSWORD
    
    menuentry 'Operational mode' {
      insmod ext2
      set root=hd0,1
      echo 'Loading Linux ...'
      linux /boot/vmlinuz root=/dev/vda1 $GRUB_CMDLINE_LINUX_DEFAULT $GRUB_CMDLINE_LINUX mode=operation
      echo 'Loading Initrd ...'
      initrd /boot/initrd
    }
    
    menuentry 'Maintenance mode' --users maintainer {
      insmod ext2
      set root=hd0,1
      echo 'Loading Linux ...'
      linux /boot/vmlinuz root=/dev/vda1 $GRUB_CMDLINE_LINUX_DEFAULT $GRUB_CMDLINE_LINUX mode=maintenance
      echo 'Loading Initrd ...'
      initrd /boot/initrd
    }
  4. Import the changes into the main configuration file:

    > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

In the above example:

  • The GRUB 2 menu has two entries, Operational mode and Maintenance mode.

  • If no user is specified, both boot menu entries are accessible, but no one can access GRUB 2 command line or edit existing menu entries.

  • admin user can access GRUB 2 command line and edit existing menu entries.

  • maintenance user can select the recovery menu item.

18.3 Configuring the boot loader with YaST

The easiest way to configure general options of the boot loader in your SUSE Linux Enterprise Server system is to use the YaST module. In the YaST Control Center, select System › Boot Loader. The module shows the current boot loader configuration of your system and allows you to make changes.

Use the Boot Code Options tab to view and change settings related to type, location and advanced loader settings. You can choose whether to use GRUB 2 in standard or EFI mode.

Important
Important: EFI systems require GRUB2-EFI

If you have an EFI system you can only install GRUB2-EFI, otherwise your system is no longer bootable.

Important
Important: Reinstalling the boot loader

To reinstall the boot loader, make sure to change a setting in YaST and then change it back. For example, to reinstall GRUB2-EFI, select GRUB2 first and then immediately switch back to GRUB2-EFI.

Otherwise, the boot loader may only be partially reinstalled.

Note
Note: Custom boot loader

To use a boot loader other than the ones listed, select Do Not Install Any Boot Loader. Read the documentation of your boot loader carefully before choosing this option.

18.3.1 Boot loader location and boot code options

The default location of the boot loader depends on the partition setup and is either the Master Boot Record (MBR) or the boot sector of the / partition. To modify the location of the boot loader, follow these steps:

Procedure 18.1: Changing the boot loader location
  1. Select the Boot Code Options tab and then choose one of the following options for Boot Loader Location:

    Boot from Master Boot Record

    This installs the boot loader in the MBR of the disk containing the directory /boot. Usually this will be the disk mounted to /, but if /boot is mounted to a separate partition on a different disk, the MBR of that disk will be used.

    Boot from Root Partition

    This installs the boot loader in the boot sector of the / partition.

    Custom Root Partition

    Use this option to specify the location of the boot loader manually.

  2. Click OK to apply the changes.

Boot code options
Figure 18.2: Boot code options

The Boot Code Options tab includes the following additional options:

Set Active Flag in Partition Table for Boot Partition

Activates the partition that contains the /boot directory. For POWER systems it activates the PReP partition. Use this option on systems with old BIOS and/or legacy operating systems because they may fail to boot from a non-active partition. It is safe to leave this option active.

Write Generic Boot Code to MBR

If MBR contains a custom 'non-GRUB' code, this option replaces it with a generic, operating system independent code. If you deactivate this option, the system may become unbootable.

Enable Trusted Boot Support

Starts TrustedGRUB2, which supports trusted computing functionality (Trusted Platform Module (TPM)). For more information refer to https://github.com/Sirrix-AG/TrustedGRUB2.

The Protective MBR flag section includes the following options:

set

This is appropriate for traditional legacy BIOS booting.

remove

This is appropriate for UEFI booting.

do not change

This is usually the best choice if you have an already working system.

In most cases YaST defaults to the appropriate choice.

18.3.2 Adjusting the disk order

If your computer has more than one hard disk, you can specify the boot sequence of the disks. The first disk in the list is where GRUB 2 will be installed in the case of booting from MBR. It is the disk where SUSE Linux Enterprise Server is installed by default. The rest of the list is a hint for GRUB 2's device mapper (see Section 18.2.4, “Mapping between BIOS drives and Linux devices”).

Warning
Warning: Unbootable system

The default value is usually valid for almost all deployments. If you change the boot order of disks wrongly, the system may become unbootable on the next reboot. For example, if the first disk in the list is not part of the BIOS boot order, and the other disks in the list have empty MBRs.

Procedure 18.2: Setting the disk order
  1. Open the Boot Code Options tab.

  2. Click Edit Disk Boot Order.

  3. If more than one disk is listed, select a disk and click Up or Down to reorder the displayed disks.

  4. Click OK two times to save the changes.

18.3.3 Configuring advanced options

Advanced boot parameters can be configured via the Boot Loader Options tab.

18.3.3.1 Boot Loader Options tab

Boot loader options
Figure 18.3: Boot loader options
Boot Loader Time-Out

Change the value of Time-Out in Seconds by typing in a new value and clicking the appropriate arrow key with your mouse.

Probe Foreign OS

When selected, the boot loader searches for other systems like Windows or other Linux installations.

Hide Menu on Boot

Hides the boot menu and boots the default entry.

Adjusting the Default Boot Entry

Select the desired entry from the Default Boot Section list. Note that the > sign in the boot entry name delimits the boot section and its subsection.

Protect Boot Loader with Password

Protects the boot loader and the system with an additional password. For details on manual configuration, see Section 18.2.6, “Setting a boot password”. If this option is activated, the boot password is required on every boot, which means the system does not boot automatically. However, if you prefer the behavior of GRUB 1, additionally enable Protect Entry Modification Only. With this setting, anybody is allowed to select a boot entry and boot the system, whereas the password for the GRUB 2 root user is only required for modifying boot entries.

18.3.3.2 Kernel Parameters tab

Kernel parameters
Figure 18.4: Kernel parameters
Optional Kernel Command Line Parameter

Specify optional kernel parameters here to enable/disable system features, add drivers, etc.

CPU Mitigations

SUSE has released one or more kernel boot command line parameters for all software mitigations that have been deployed to prevent CPU side-channel attacks. Some of those may result in performance loss. Choose one the following options to strike a balance between security and performance, depending on your setting:

Auto Enables all mitigations required for your CPU model, but does not protect against cross-CPU thread attacks. This setting may impact performance to some degree, depending on the workload.

Auto + No SMT Provides the full set of available security mitigations. Enables all mitigations required for your CPU model. In addition, it disables Simultaneous Multithreading (SMT) to avoid side-channel attacks across multiple CPU threads. This setting may further impact performance, depending on the workload.

Off Disables all mitigations. Side-channel attacks against your CPU are possible, depending on the CPU model. This setting has no impact on performance.

Manual Does not set any mitigation level. Specify your CPU mitigations manually by using the kernel command line options.

Use Graphical Console

When checked, the boot menu appears on a graphical splash screen rather than in a text mode. The resolution of the boot screen is set automatically by default, but you can manually set it via Console resolution. The graphical theme definition file can be specified with the Console theme file chooser. Only change this if you want to apply your own, custom-made theme.

Use Serial Console

If your machine is controlled via a serial console, activate this option and specify which COM port to use at which speed. See info grub or https://www.gnu.org/software/grub/manual/grub.html#Serial-terminal

18.4 Differences in terminal usage on IBM Z

On 3215 and 3270 terminals there are certain differences and limitations on how to move the cursor and how to issue editing commands within GRUB 2.

18.4.1 Limitations

Interactivity

Interactivity is strongly limited. Typing often does not result in visual feedback. To see where the cursor is, type an underscore (_).

Note
Note: 3270 compared to 3215

The 3270 terminal is much better at displaying and refreshing screens than the 3215 terminal.

Cursor movement

Traditional cursor movement is not possible. Alt, Meta, Ctrl and the cursor keys do not work. To move the cursor, use the key combinations listed in Section 18.4.2, “Key combinations”.

Caret

The caret (^) is used as a control character. To type a literal ^ followed by a letter, type ^, ^, LETTER.

Enter

The Enter key does not work, use ^J instead.

18.4.2 Key combinations

Common Substitutes:

^J

engage (Enter)

^L

abort, return to previous state

^I

tab completion (in edit and shell mode)

Keys Available in Menu Mode:

^A

first entry

^E

last entry

^P

previous entry

^N

next entry

^G

previous page

^C

next page

^F

boot selected entry or enter submenu (same as ^J)

E

edit selected entry

C

enter GRUB-Shell

Keys Available in Edit Mode:

^P

previous line

^N

next line

^B

backward char

^F

forward char

^A

beginning of line

^E

end of line

^H

backspace

^D

delete

^K

kill line

^Y

yank

^O

open line

^L

refresh screen

^X

boot entry

^C

enter GRUB-Shell

Keys Available in Command Line Mode:

^P

previous command

^N

next command from history

^A

beginning of line

^E

end of line

^B

backward char

^F

forward char

^H

backspace

^D

delete

^K

kill line

^U

discard line

^Y

yank

18.5 Helpful GRUB 2 commands

grub2-mkconfig

Generates a new /boot/grub2/grub.cfg based on /etc/default/grub and the scripts from /etc/grub.d/.

Example 18.1: Usage of grub2-mkconfig
grub2-mkconfig -o /boot/grub2/grub.cfg
Tip
Tip: Syntax check

Running grub2-mkconfig without any parameters prints the configuration to STDOUT where it can be reviewed. Use grub2-script-check after /boot/grub2/grub.cfg has been written to check its syntax.

Important
Important: grub2-mkconfig cannot repair UEFI Secure Boot tables

If you are using UEFI Secure Boot and your system is not reaching GRUB 2 correctly anymore, you may need to additionally reinstall the Shim and regenerate the UEFI boot table. To do so, use:

# shim-install --config-file=/boot/grub2/grub.cfg
grub2-mkrescue

Creates a bootable rescue image of your installed GRUB 2 configuration.

Example 18.2: Usage of grub2-mkrescue
grub2-mkrescue -o save_path/name.iso iso
grub2-script-check

Checks the given file for syntax errors.

Example 18.3: Usage of grub2-script-check
grub2-script-check /boot/grub2/grub.cfg
grub2-once

Set the default boot entry for the next boot only. To get the list of available boot entries use the --list option.

Example 18.4: Usage of grub2-once
grub2-once number_of_the_boot_entry
Tip
Tip: grub2-once help

Call the program without any option to get a full list of all possible options.

18.6 Rescue mode

Rescue mode is a specific root user session for troubleshooting and repairing systems where the booting process fails. It offers a single-user environment with local file systems and core system services active. Network interfaces are not activated. To enter the rescue mode, follow these steps.

Procedure 18.3: Entering rescue mode
  1. Reboot the system. The boot screen appears, offering the GRUB 2 boot menu.

  2. Select the menu entry to boot and press e to edit the boot line.

  3. Append the following parameter to the line containing the kernel parameters:

    systemd.unit=rescue.target
  4. Press Ctrl+X to boot with these settings.

  5. Enter the password for root.

  6. Make all the necessary changes.

  7. Enter normal operating target again by entering systemctl isolate multi-user.target or systemctl isolate graphical.target at the command line.

18.7 More information

Extensive information about GRUB 2 is available at https://www.gnu.org/software/grub/. Also refer to the grub info page. You can also search for the keyword GRUB 2 in the Technical Information Search at https://www.suse.com/support to get information about special issues.

19 The systemd daemon

systemd initializes the system. It has the process ID 1. systemd is started directly by the kernel and resists signal 9, which normally terminates processes. All other programs are started directly by systemd or by one of its child processes. systemd is a replacement for the System V init daemon and is fully compatible with System V init (by supporting init scripts).

The main advantage of systemd is that it considerably speeds up boot time by parallelizing service starts. Furthermore, systemd only starts a service when it is really needed. Daemons are not started unconditionally at boot time, but when being required for the first time. systemd also supports Kernel Control Groups (cgroups), creating snapshots, and restoring the system state. For more details see https://www.freedesktop.org/wiki/Software/systemd/.

19.1 The systemd concept

The following section explains the concept behind systemd.

systemd is a system and session manager for Linux, compatible with System V and LSB init scripts. The main features of systemd include:

  • parallelization capabilities

  • socket and D-Bus activation for starting services

  • on-demand starting of daemons

  • tracking of processes using Linux cgroups

  • creating snapshots and restoring of the system state

  • maintains mount and automount points

  • implements an elaborate transactional dependency-based service control logic

19.1.1 Unit file