This guide describes the administration of SUSE Linux Enterprise Micro.
Copyright © 2006–2025 SUSE LLC and contributors. All rights reserved.
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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: Latest updatesThe latest updates are usually available in the English-language version of this documentation.
- SUSE Knowledgebase
If you run into an issue, 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 theman
command is not installed on your system, install it withsudo 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 .
- Bug reports
Report issues with the documentation at https://bugzilla.suse.com/.
To simplify this process, click the
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
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:only available for EnglishThe
icons are only available for the English version of each document. For all other languages, use the icons instead.For more information about the documentation environment used for this documentation, see the repository's README.
You can also report errors and send feedback concerning the documentation to <doc-team@suse.com>. 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 namesPLACEHOLDER: Replace PLACEHOLDER with the actual value
PATH
: An environment variablels
,--help
: Commands, options, and parametersuser
: The name of a user or grouppackage_name: The name of a software package
Alt, Alt–F1: A key to press or a key combination. Keys are shown in uppercase as on a keyboard.
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
andPOWER
. 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 thesudo
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 end of the line:>
echo
a b \ c dA code block that shows both the command (preceded by a prompt) and the respective output returned by the shell:
>
command
outputNotices
Warning: Warning noticeVital 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 noticeImportant information you should be aware of before proceeding.
Note: Note noticeAdditional information, for example about differences in software versions.
Tip: Tip noticeHelpful information, like a guideline or a piece of practical advice.
Compact Notices
Additional information, for example about differences in software versions.
Helpful information, like a guideline or a piece of practical advice.
4 Support #
Find the support statement for SUSE Linux Enterprise Micro 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 Micro #
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 Micro 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.
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 Read-only file system
This chapter focuses on the characteristics of the read-only file system that is used by SLE Micro.
- 2 Snapshots
This chapter describes managing snapshots and gives details about directories included in snapshots.
- 3 Administration using transactional updates
This chapter describes the usage of the
transactional-update
command.- 4 User space live patching
This chapter describes the basic principles and usage of user space live patching.
1 Read-only file system #
This chapter focuses on the characteristics of the read-only file system that is used by SLE Micro.
SLE Micro was designed to use a read-only root file system. This means that
after the deployment is complete, you are not able to perform direct
modifications to the root file system, e.g. by using
zypper
. Instead, SUSE Linux Enterprise Micro introduces the concept of
transactional updates which enables you to modify your system and keep it up
to date.
The key features of transactional updates are the following:
They are atomic - the update is applied only if it completes successfully.
Changes are applied in a separate snapshot and so do not influence the running system.
Changes can easily be rolled back.
Each time you call the transactional-update
command to
change your system—either to install a package, perform an update or
apply a patch—the following actions take place:
A new read-write snapshot is created from your current root file system, or from a snapshot that you specified.
All changes are applied (updates, patches or package installation).
The snapshot is switched back to read-only mode.
If the changes were applied successfully, the new root file system snapshot is set as default.
After rebooting, the system boots into the new snapshot.
NoteBear in mind that without rebooting your system, the changes will not be applied.
In case you do not reboot your machine before performing further changes,
the transactional-update
command will create a new
snapshot from the current root file system. This means that you will end up
with several parallel snapshots, each including that particular change but
not changes from the other invocations of the command. After reboot, the
most recently created snapshot will be used as your new root file system,
and it will not include changes done in the previous snapshots.
1.1 /etc
on a read-only file system #
Even though /etc
is part of the read-only file system,
using an OverlayFS
layer on this directory enables you to
write to this directory. All modifications that you performed on the content
of /etc
are written to the
/var/lib/overlay/SNAPSHOT_NUMBER/etc
.
Each snapshot has one associated OverlayFS
directory.
Whenever a new snapshot is created (for example, as a result of a system
update), the content of /etc
is synchronized and used
as a base in the new snapshot. In the OverlayFS
terminology, the current snapshot's /etc
is mounted as
lowerdir
. The new snapshot's /etc
is
mounted as upperdir
. If there were no changes in the
upperdir
/etc
, any changes performed
to the lowerdir
are visible to the
upperdir
. Therefore, the new snapshot also contains the
changes from the current snapshot's /etc
.
lowerdir
and upperdir
If /etc
in both snapshots is modified, only the changes in the new snapshot (upperdir
) persist. Changes made to the current snapshot (lowerdir
) are not synchronized to the new snapshot. Therefore, we do not recommend changing /etc
after a new snapshot has been created and the system has not been rebooted. However, you can still find the changes in the /var/lib/overlay/
directory for the snapshot in which the changes were performed.
--continue
option of the transactional-update
command
If you use the --continue
option of the transactional-update
command when performing changes to the file system, all /etc
directory layers created by each separate run of transactional-update
, except for the one in the newest snapshot, are synchronized to the lowerdir
(the lowerdir
can have several mount points).
2 Snapshots #
This chapter describes managing snapshots and gives details about directories included in snapshots.
As snapshots are crucial for the correct functioning of SLE Micro, do not disable the feature, and ensure that the root partition is big enough to store the snapshots.
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.
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 which do not contain 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.
Snapshots that are known to be working properly are marked as important.
2.1 Directories excluded from snapshots #
As some directories store user-specific or volatile data, these directories are excluded from snapshots:
/home
Contains users' data. Excluded so that the data will not be included in snapshots and thus potentially overwritten by a rollback operation.
/root
Contains root's data. Excluded so that the data will not be included in snapshots and thus potentially overwritten by a rollback operation.
/opt
Third-party products usually get installed to
/opt
. Excluded so that these applications are not uninstalled during rollbacks./srv
Contains data for Web and FTP servers. Excluded in order to avoid data loss on rollbacks.
/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, a separate subvolume is created with Copy-On-Write disabled, so as to exclude all of this variable data from snapshots./tmp
The directory contains temporary data.
- the architecture-specific
/boot/grub2
directory Rollback of the boot loader binaries is not supported.
2.2 Showing exclusive disk space used by snapshots #
Snapshots share data, for efficient use of storage space, so using ordinary
commands like du
and df
won't 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. The btrfs
command provides a 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 /
3 Administration using transactional updates #
This chapter describes the usage of the
transactional-update
command.
In case you do not reboot your machine before performing further changes,
the transactional-update
command will create a new
snapshot from the current root file system. This means that you will end
up with several parallel snapshots, each including that particular change
but not changes from the other invocations of the command. After reboot,
the most recently created snapshot will be used as your new root file
system, and it will not include changes done in the previous snapshots.
3.1 transactional-update
usage #
The transactional-update
command enables the 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
and uses it to update the system. Later you can restore this snapshot. All
changes become active only after reboot.
The transactional-update
command syntax is as follows:
transactional-update [option]
[general_command] [package_command] standalone_command
transactional-update
without arguments
If you do not specify any command or option while running the
transactional-update
command, the system updates
itself.
Possible command parameters are described further.
transactional-update
options #--interactive, -i
Can be used along with a package command to turn on interactive mode.
--non-interactive, -n
Can be used along with a package command to turn on non-interactive mode.
--continue [number], -c
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, runtransactional-update
again to install the forgotten package, and reboot again. You cannot run thetransactional-update
command multiple times without rebooting to add more changes to the snapshot, because this will create 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 that you may select any existing snapshot as the base for your new snapshot. The following example demonstrates runningtransactional-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
--no-selfupdate
Disables self-updating of
transactional-update
.--drop-if-no-change, -d
Discards the snapshot created by
transactional-update
if there were no changes to the root file system. If there are some changes to the/etc
directory, those changes are merged back to the current file system.--quiet
The
transactional-update
command will not output tostdout
.--help, -h
Prints help for the
transactional-update
command.--version
Displays the version of the
transactional-update
command.
The general commands are the following:
cleanup-snapshots
The command marks all unused snapshots that are intended to be removed.
cleanup-overlays
The command removes all unused overlay layers of
/etc
.cleanup
The command combines the
cleanup-snapshots
andcleanup-overlays
commands. For more details, refer to Section 3.2, “Snapshots cleanup”.grub.cfg
Use this command to rebuild the GRUB boot loader configuration file.
bootloader
The command reinstalls the boot loader.
initrd
Use the command to rebuild
initrd
.kdump
If you perform changes to your hardware or storage, you may need to rebuild the kdump initrd.
shell
Opens a read-write shell in the new snapshot before exiting. The command is typically used for debugging purposes.
reboot
The system reboots after the transactional-update is complete.
run
<command>Runs the provided command in a new snapshot.
setup-selinux
Installs and enables the targeted SELinux policy.
The package commands are the following:
The installation of packages from repositories other than
the official ones (for example, the SUSE Linux Enterprise Server repositories) is
not supported and not
recommended. To use the tools available for SUSE Linux Enterprise Server, run the
toolbox
container and install the tools inside
the container. For details about the toolbox
container, refer to Chapter 9, toolbox
for SLE Micro debugging.
dup
Performs an upgrade of your system. The default option for this command is
--non-interactive
.migration
The command migrates your system to a selected target. Typically, it is used to upgrade your system if it has been registered via SUSE Customer Center.
patch
Checks for available patches and installs them. The default option for this command is
--non-interactive
.pkg 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. The default option for this command is--interactive
.#
transactional-update pkg install package_name
or
#
transactional-update pkg install rpm1 rpm2
pkg remove
Removes individual packages from the active snapshot using the
zypper remove
command. This command can also be used to remove PTF RPM files. The default option for this command is--interactive
.#
transactional-update pkg remove package_name
pkg 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. The default option for this command is--interactive
.#
transactional-update pkg update package_name
register
The
register
command enables you to register/deregister your system. For a complete usage description, refer to Section 3.1.1, “Theregister
command”.up
Updates installed packages to newer versions. The default option for this command is
--non-interactive
.
The standalone commands are the following:
rollback
<snapshot number>This sets the default subvolume. The current system is set as the 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
rollback last
This command sets the last known to be working snapshot as the default.
3.1.1 The register
command #
The register
command enables you to handle all tasks
regarding registration and subscription management. You can supply the
following options:
--list-extensions
With this option, the command will list available extensions for your system. You can use the output to find a product identifier for product activation.
-p, --product
Use this option to specify a product for activation. The product identifier has the following format: <name>/<version>/<architecture>, for example,
sle-module-live-patching/15.3/x86_64
. The appropriate command will then be the following:#
transactional-update register -p sle-module-live-patching/15.3/x86_64-r, --regcode
Register your system with the provided registration code. The command will register the subscription and enable software repositories.
-d, --de-register
The option deregisters the system, or when used along with the
-p
option, deregisters an extension.-e, --email
Specify an email address that will be used in SUSE Customer Center for registration.
--url
Specify the URL of your registration server. The URL is stored in the configuration and will be used in subsequent command invocations. For example:
#
transactional-update register --url https://scc.suse.com-s, --status
Displays the current registration status in JSON format.
--write-config
Writes the provided options value to the
/etc/SUSEConnect
configuration file.--cleanup
Removes old system credentials.
--version
Prints the version.
--help
Displays the usage of the command.
3.2 Snapshots cleanup #
If you run the command transactional-update cleanup
,
all old snapshots without a cleanup algorithm will have one set. All
important snapshots are also marked. The command also removes all
unreferenced (and thus unused) /etc
overlay
directories in /var/lib/overlay
.
The snapshots with the set number
cleanup algorithm
will be deleted according to the rules configured in
/etc/snapper/configs/root
by the following
parameters:
- NUMBER_MIN_AGE
Defines the minimum age of a snapshot (in seconds) that can be automatically removed.
- NUMBER_LIMIT/NUMBER_LIMIT_IMPORTANT
Defines the maximum count of stored snapshots. The cleaning algorithms delete snapshots above the specified maximum value, without taking into account the snapshot and file system space. The algorithms also delete snapshots above the minimum value until the limits for the snapshot and file system are reached.
The snapshot cleanup is also regularly performed by systemd
.
3.3 System rollback #
GRUB 2 enables booting from btrfs snapshots and thus allows you to use any older functional snapshot in case the new snapshot does not work correctly.
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.
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
.
There are two methods to perform a system rollback.
From a running system, you can set the default snapshot, see more in Procedure 3.1, “Rollback from a running system”.
Especially in cases where the current snapshot is broken, you can boot into the new snapshot and set it to default. For details, refer to Procedure 3.2, “Rollback to a working snapshot”.
If your current snapshot is functional, you can use the following procedure for a system rollback.
Choose the snapshot that should be set as default, run:
#
snapper listto get a list of available snapshots. Note the number of the snapshot to be set as default.
Set the snapshot as default by running:
#
transactional-update rollback snapshot_numberIf you omit the snapshot number, the current snapshot will be set as default.
Reboot your system to boot into the new default snapshot.
The following procedure is used in case the current snapshot is broken and you are not able to boot into it.
Reboot your system and select
Start bootloader from a read-only snapshot
.Choose a snapshot to boot. The snapshots are sorted according to the date of creation, with the latest one at the top.
Log in to your system and check whether everything works as expected. The data written to directories excluded from the snapshots will stay untouched.
If the snapshot you booted into is not suitable for the rollback, reboot your system and choose another one.
If the snapshot works as expected, you can perform the rollback by running the following command:
#
transactional-update rollback
And reboot afterwards.
3.4 Managing automatic transactional updates #
Automatic updates are controlled by 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)
documentation.
You can disable automatic transactional updates with this command:
#
systemctl --now disable transactional-update.timer
4 User space live patching #
This chapter describes the basic principles and usage of user space live patching.
4.1 About user space live patching #
On SLE Micro, ULP is a technical preview only.
Only the currently running processes are affected by the live patches. As the libraries are changed in the new snapshot and not in the current one, new processes started in the current snapshot still use the non-patched libraries until you reboot. After the reboot, the system switches to the new snapshot and all started processes will use the patched libraries.
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.
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
.
4.1.1 Prerequisites #
For ULP to work, two requirements must be met.
Install the ULP on your system by running:
>
transactional-update pkg in libpulp0 libpulp-toolsAfter successful installation, reboot your system.
Applications with desired live patch support must be launched preloading the
libpulp.so.0
library. See Section 4.1.3, “Usinglibpulp
” for more details.
4.1.2 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-1_1-livepatches packages:
>
transactional-update pkg in glibc-livepatches openssl-1_1-livepatches
After successful installation, reboot your system.
4.1.3 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
4.1.3.1 Checking if a library is live patchable #
To check whether a library is live patchable, use the following command:
>
ulp livepatchable PATH_TO_LIBRARY
4.1.3.2 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.
4.1.3.3 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 4.1.3.6, “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.
4.1.3.4 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
4.1.3.5 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
4.1.3.6 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
4.2 More information #
Further information about libpulp
is available
in the project's Git
repository.
Part II Networking #
- 5 Basic networking
Linux offers the necessary networking tools and features for integration into all types of network structures. Network access using a network card can be configured with YaST. Manual configuration is also possible. In this chapter, only the fundamental mechanisms and the relevant network configuration files are covered.
- 6 NetworkManager and
wicked
This chapter focuses on the difference between NetworkManager and
wicked
and provides a description how to switch fromwicked
to NetworkManager.- 7 NetworkManager configuration and usage
NetworkManager is shipped so it can run out of the box, but you might need to reconfigure or restart the tool. This chapter focuses on these tasks.
5 Basic networking #
Linux offers the necessary networking tools and features for integration into all types of network structures. Network access using a network card can be configured with YaST. Manual configuration is also possible. In this chapter, only the fundamental mechanisms and the relevant network configuration files are covered.
Linux and other Unix operating systems use the TCP/IP protocol. It is not a single network protocol, but a family of network protocols that offer various services. The protocols listed in Several protocols in the TCP/IP protocol family are provided for exchanging data between two machines via TCP/IP. Networks combined by TCP/IP, comprising a worldwide network, are also called “the Internet.”
RFC stands for Request for Comments. RFCs are documents that describe various Internet protocols and implementation procedures for the operating system and its applications. The RFC documents describe the setup of Internet protocols. For more information about RFCs, see https://datatracker.ietf.org/.
- TCP
Transmission Control Protocol: a connection-oriented secure protocol. The data to transmit is first sent by the application as a stream of data and converted into the appropriate format by the operating system. The data arrives at the respective application on the destination host in the original data stream format it was initially sent. TCP determines whether any data has been lost or jumbled during the transmission. TCP is implemented wherever the data sequence matters.
- UDP
User Datagram Protocol: a connectionless, insecure protocol. The data to transmit is sent in the form of packets generated by the application. The order in which the data arrives at the recipient is not guaranteed and data loss is possible. UDP is suitable for record-oriented applications. It features a smaller latency period than TCP.
- ICMP
Internet Control Message Protocol: This is not a protocol for the end user, but a special control protocol that issues error reports and can control the behavior of machines participating in TCP/IP data transfer. In addition, it provides a special echo mode that can be viewed using the program ping.
- IGMP
Internet Group Management Protocol: This protocol controls machine behavior when implementing IP multicast.
As shown in Figure 5.1, “Simplified layer model for TCP/IP”, data exchange takes place in different layers. The actual network layer is the insecure data transfer via IP (Internet protocol). On top of IP, TCP (transmission control protocol) guarantees, to a certain extent, security of the data transfer. The IP layer is supported by the underlying hardware-dependent protocol, such as Ethernet.
The diagram provides one or two examples for each layer. The layers are ordered according to abstraction levels. The lowest layer is very close to the hardware. The uppermost layer, however, is almost a complete abstraction from the hardware. Every layer has its own special function. The special functions of each layer are mostly implicit in their description. The data link and physical layers represent the physical network used, such as Ethernet.
Almost all hardware protocols work on a packet-oriented basis. The data to transmit is collected into packets (it cannot be sent all at once). The maximum size of a TCP/IP packet is approximately 64 KB. Packets are normally quite small, as the network hardware can be a limiting factor. The maximum size of a data packet on Ethernet is about fifteen hundred bytes. The size of a TCP/IP packet is limited to this amount when the data is sent over Ethernet. If more data is transferred, more data packets need to be sent by the operating system.
For the layers to serve their designated functions, additional information regarding each layer must be saved in the data packet. This takes place in the header of the packet. Every layer attaches a small block of data, called the protocol header, to the front of each emerging packet. A sample TCP/IP data packet traveling over an Ethernet cable is illustrated in Figure 5.2, “TCP/IP Ethernet packet”. The proof sum is located at the end of the packet, not at the beginning. This simplifies things for the network hardware.
When an application sends data over the network, the data passes through each layer, all implemented in the Linux kernel except the physical layer. Each layer is responsible for preparing the data so it can be passed to the next layer. The lowest layer is ultimately responsible for sending the data. The entire procedure is reversed when data is received. Like the layers of an onion, in each layer the protocol headers are removed from the transported data. Finally, the transport layer is responsible for making the data available for use by the applications at the destination. In this manner, one layer only communicates with the layer directly above or below it. For applications, it is irrelevant whether data is transmitted via a wireless or wired connection. Likewise, it is irrelevant for the data line which kind of data is transmitted, as long as packets are in the correct format.
5.1 IP addresses and routing #
The discussion in this section is limited to IPv4 networks. For information about IPv6 protocol, the successor to IPv4, refer to Section 5.2, “IPv6—the next generation Internet”.
5.1.1 IP addresses #
Every computer on the Internet has a unique 32-bit address. These 32 bits (or 4 bytes) are normally written as illustrated in the second row in Example 5.1, “Writing IP addresses”.
IP Address (binary): 11000000 10101000 00000000 00010100 IP Address (decimal): 192. 168. 0. 20
In decimal form, the four bytes are written in the decimal number system, separated by periods. The IP address is assigned to a host or a network interface. It can be used only once throughout the world. There are exceptions to this rule, but these are not relevant to the following passages.
The points in IP addresses indicate the hierarchical system. Until the 1990s, IP addresses were strictly categorized in classes. However, this system proved too inflexible and was discontinued. Now, classless routing (CIDR, classless interdomain routing) is used.
5.1.2 Netmasks and routing #
Netmasks are used to define the address range of a subnet. If two hosts are in the same subnet, they can reach each other directly. If they are not in the same subnet, they need the address of a gateway that handles all the traffic for the subnet. To check if two IP addresses are in the same subnet, simply “AND” both addresses with the netmask. If the result is identical, both IP addresses are in the same local network. If there are differences, the remote IP address, and thus the remote interface, can only be reached over a gateway.
To understand how the netmask works, look at
Example 5.2, “Linking IP addresses to the netmask”. The netmask consists of 32 bits
that identify how much of an IP address belongs to the network. All those
bits that are 1
mark the corresponding bit in the IP
address as belonging to the network. All bits that are 0
mark bits inside the subnet. This means that the more bits are
1
, the smaller the subnet is. Because the netmask always
consists of several successive 1
bits, it is also
possible to count the number of bits in the netmask. In
Example 5.2, “Linking IP addresses to the netmask” the first net with 24 bits could
also be written as 192.168.0.0/24
.
IP address (192.168.0.20): 11000000 10101000 00000000 00010100 Netmask (255.255.255.0): 11111111 11111111 11111111 00000000 --------------------------------------------------------------- Result of the link: 11000000 10101000 00000000 00000000 In the decimal system: 192. 168. 0. 0 IP address (213.95.15.200): 11010101 10111111 00001111 11001000 Netmask (255.255.255.0): 11111111 11111111 11111111 00000000 --------------------------------------------------------------- Result of the link: 11010101 10111111 00001111 00000000 In the decimal system: 213. 95. 15. 0
To give another example: all machines connected with the same Ethernet cable are usually located in the same subnet and are directly accessible. Even when the subnet is physically divided by switches or bridges, these hosts can still be reached directly.
IP addresses outside the local subnet can only be reached if a gateway is configured for the target network. In the most common case, there is only one gateway that handles all traffic that is external. However, it is also possible to configure several gateways for different subnets.
If a gateway has been configured, all external IP packets are sent to the appropriate gateway. This gateway then attempts to forward the packets in the same manner—from host to host—until it reaches the destination host or the packet's TTL (time to live) expires.
- Base Network Address
This is the netmask AND any address in the network, as shown in Example 5.2, “Linking IP addresses to the netmask” under
Result
. This address cannot be assigned to any hosts.- Broadcast Address
This could be paraphrased as: “Access all hosts in this subnet.” To generate this, the netmask is inverted in binary form and linked to the base network address with a logical OR. The above example therefore results in 192.168.0.255. This address cannot be assigned to any hosts.
- Local Host
The address
127.0.0.1
is assigned to the “loopback device” on each host. A connection can be set up to your own machine with this address and with all addresses from the complete127.0.0.0/8
loopback network as defined with IPv4. With IPv6 there is only one loopback address (::1
).
Because IP addresses must be unique all over the world, you cannot select random addresses. There are three address domains to use if you want to set up a private IP-based network. These cannot get any connection from the rest of the Internet, because they cannot be transmitted over the Internet. These address domains are specified in RFC 1597 and listed in Table 5.1, “Private IP address domains”.
Network/Netmask |
Domain |
---|---|
|
|
|
|
|
|
5.2 IPv6—the next generation Internet #
Because of the emergence of the World Wide Web (WWW), the Internet has experienced explosive growth, with an increasing number of computers communicating via TCP/IP in the past fifteen years. Since Tim Berners-Lee at CERN (http://public.web.cern.ch) invented the WWW in 1990, the number of Internet hosts has grown from a few thousand to about a hundred million.
As mentioned, an IPv4 address consists of only 32 bits. Also, quite a few IP addresses are lost—they cannot be used because of the way in which networks are organized. The number of addresses available in your subnet is two to the power of the number of bits, minus two. A subnet has, for example, 2, 6, or 14 addresses available. To connect 128 hosts to the Internet, for example, you need a subnet with 256 IP addresses, from which only 254 are usable, because two IP addresses are needed for the structure of the subnet itself: the broadcast and the base network address.
Under the current IPv4 protocol, DHCP or NAT (network address translation) are the typical mechanisms used to circumvent the potential address shortage. Combined with the convention to keep private and public address spaces separate, these methods can certainly mitigate the shortage. To set up a host in an IPv4 network, you need several address items, such as the host's own IP address, the subnetmask, the gateway address, and maybe a name server address. All these items need to be known and cannot be derived from somewhere else.
With IPv6, both the address shortage and the complicated configuration should be a thing of the past. The following sections tell more about the improvements and benefits brought by IPv6 and about the transition from the old protocol to the new one.
5.2.1 Advantages #
The most important and most visible improvement brought by the IPv6 protocol is the enormous expansion of the available address space. An IPv6 address is made up of 128 bit values instead of the traditional 32 bits. This provides for as many as several quadrillion IP addresses.
However, IPv6 addresses are not only different from their predecessors with regard to their length. They also have a different internal structure that may contain more specific information about the systems and the networks to which they belong. More details about this are found in Section 5.2.2, “Address types and structure”.
The following is a list of other advantages of the IPv6 protocol:
- Autoconfiguration
IPv6 makes the network “plug and play” capable, which means that a newly configured system integrates into the (local) network without any manual configuration. The new host uses its automatic configuration mechanism to derive its own address from the information made available by the neighboring routers, relying on a protocol called the neighbor discovery (ND) protocol. This method does not require any intervention on the administrator's part and there is no need to maintain a central server for address allocation—an additional advantage over IPv4, where automatic address allocation requires a DHCP server.
Nevertheless if a router is connected to a switch, the router should send periodic advertisements with flags telling the hosts of a network how they should interact with each other. For more information, see RFC 2462 and the
radvd.conf(5)
man page, and RFC 3315.- Mobility
IPv6 makes it possible to assign several addresses to one network interface at the same time. This allows users to access several networks easily, something that could be compared with the international roaming services offered by mobile phone companies. When you take your mobile phone abroad, the phone automatically logs in to a foreign service when it enters the corresponding area, so you can be reached under the same number everywhere and can place an outgoing call, as you would in your home area.
- Secure communication
With IPv4, network security is an add-on function. IPv6 includes IPsec as one of its core features, allowing systems to communicate over a secure tunnel to avoid eavesdropping by outsiders on the Internet.
- Backward compatibility
Realistically, it would be impossible to switch the entire Internet from IPv4 to IPv6 at one time. Therefore, it is crucial that both protocols can coexist not only on the Internet, but also on one system. This is ensured by compatible addresses (IPv4 addresses can easily be translated into IPv6 addresses) and by using several tunnels. See Section 5.2.3, “Coexistence of IPv4 and IPv6”. Also, systems can rely on a dual stack IP technique to support both protocols at the same time, meaning that they have two network stacks that are completely separate, such that there is no interference between the two protocol versions.
5.2.2 Address types and structure #
As mentioned, the current IP protocol has two major limitations: there is an increasing shortage of IP addresses and configuring the network and maintaining the routing tables is becoming a more complex and burdensome task. IPv6 solves the first problem by expanding the address space to 128 bits. The second one is mitigated by introducing a hierarchical address structure combined with sophisticated techniques to allocate network addresses, and multihoming (the ability to assign several addresses to one device, giving access to several networks).
When dealing with IPv6, it is useful to know about three different types of addresses:
- Unicast
Addresses of this type are associated with exactly one network interface. Packets with such an address are delivered to only one destination. Accordingly, unicast addresses are used to transfer packets to individual hosts on the local network or the Internet.
- Multicast
Addresses of this type relate to a group of network interfaces. Packets with such an address are delivered to all destinations that belong to the group. Multicast addresses are mainly used by certain network services to communicate with certain groups of hosts in a well-directed manner.
- Anycast
Addresses of this type are related to a group of interfaces. Packets with such an address are delivered to the member of the group that is closest to the sender, according to the principles of the underlying routing protocol. Anycast addresses are used to make it easier for hosts to find out about servers offering certain services in the given network area. All servers of the same type have the same anycast address. Whenever a host requests a service, it receives a reply from the server with the closest location, as determined by the routing protocol. If this server should fail for some reason, the protocol automatically selects the second closest server, then the third one, and so forth.
An IPv6 address is made up of eight four-digit fields, each representing 16
bits, written in hexadecimal notation. They are separated by colons
(:
). Any leading zero bytes within a given field may be
dropped, but zeros within the field or at its end may not. Another
convention is that more than four consecutive zero bytes may be collapsed
into a double colon. However, only one such ::
is
allowed per address. This kind of shorthand notation is shown in
Example 5.3, “Sample IPv6 address”, where all three lines represent the
same address.
fe80 : 0000 : 0000 : 0000 : 0000 : 10 : 1000 : 1a4 fe80 : 0 : 0 : 0 : 0 : 10 : 1000 : 1a4 fe80 : : 10 : 1000 : 1a4
Each part of an IPv6 address has a defined function. The first bytes form
the prefix and specify the type of address. The center part is the network
portion of the address, but it may be unused. The end of the address forms
the host part. With IPv6, the netmask is defined by indicating the length
of the prefix after a slash at the end of the address. An address, as shown
in Example 5.4, “IPv6 address specifying the prefix length”, contains the information that the
first 64 bits form the network part of the address and the last 64 form its
host part. In other words, the 64
means that the netmask
is filled with 64 1-bit values from the left. As with IPv4, the IP address
is combined with AND with the values from the netmask to determine whether
the host is located in the same subnet or in another one.
fe80::10:1000:1a4/64
IPv6 knows about several predefined types of prefixes. Some are shown in Various IPv6 prefixes.
00
IPv4 addresses and IPv4 over IPv6 compatibility addresses. These are used to maintain compatibility with IPv4. Their use still requires a router able to translate IPv6 packets into IPv4 packets. Several special addresses, such as the one for the loopback device, have this prefix as well.
2
or3
as the first digitAggregatable global unicast addresses. As is the case with IPv4, an interface can be assigned to form part of a certain subnet. Currently, there are the following address spaces:
2001::/16
(production quality address space) and2002::/16
(6to4 address space).fe80::/10
Link-local addresses. Addresses with this prefix should not be routed and should therefore only be reachable from within the same subnet.
fec0::/10
Site-local addresses. These may be routed, but only within the network of the organization to which they belong. In effect, they are the IPv6 equivalent of the current private network address space, such as
10.x.x.x
.ff
These are multicast addresses.
A unicast address consists of three basic components:
- Public topology
The first part (which also contains one of the prefixes mentioned above) is used to route packets through the public Internet. It includes information about the company or institution that provides the Internet access.
- Site topology
The second part contains routing information about the subnet to which to deliver the packet.
- Interface ID
The third part identifies the interface to which to deliver the packet. This also allows for the MAC to form part of the address. Given that the MAC is a globally unique, fixed identifier coded into the device by the hardware maker, the configuration procedure is substantially simplified. In fact, the first 64 address bits are consolidated to form the
EUI-64
token, with the last 48 bits taken from the MAC, and the remaining 24 bits containing special information about the token type. This also makes it possible to assign anEUI-64
token to interfaces that do not have a MAC, such as those based on point-to-point protocol (PPP).
On top of this basic structure, IPv6 distinguishes between five different types of unicast addresses:
::
(unspecified)This address is used by the host as its source address when the interface is initialized for the first time (at which point, the address cannot yet be determined by other means).
::1
(loopback)The address of the loopback device.
- IPv4 compatible addresses
The IPv6 address is formed by the IPv4 address and a prefix consisting of 96 zero bits. This type of compatibility address is used for tunneling (see Section 5.2.3, “Coexistence of IPv4 and IPv6”) to allow IPv4 and IPv6 hosts to communicate with others operating in a pure IPv4 environment.
- IPv4 addresses mapped to IPv6
This type of address specifies a pure IPv4 address in IPv6 notation.
- Local addresses
There are two address types for local use:
- link-local
This type of address can only be used in the local subnet. Packets with a source or target address of this type should not be routed to the Internet or other subnets. These addresses contain a special prefix (
fe80::/10
) and the interface ID of the network card, with the middle part consisting of zero bytes. Addresses of this type are used during automatic configuration to communicate with other hosts belonging to the same subnet.- site-local
Packets with this type of address may be routed to other subnets, but not to the wider Internet—they must remain inside the organization's own network. Such addresses are used for intranets and are an equivalent of the private address space defined by IPv4. They contain a special prefix (
fec0::/10
), the interface ID, and a 16-bit field specifying the subnet ID. Again, the rest is filled with zero bytes.
As a completely new feature introduced with IPv6, each network interface normally gets several IP addresses, with the advantage that several networks can be accessed through the same interface. One of these networks can be configured completely automatically using the MAC and a known prefix with the result that all hosts on the local network can be reached when IPv6 is enabled (using the link-local address). With the MAC forming part of it, any IP address used in the world is unique. The only variable parts of the address are those specifying the site topology and the public topology, depending on the actual network in which the host is currently operating.
For a host to go back and forth between different networks, it needs at least two addresses. One of them, the home address, not only contains the interface ID but also an identifier of the home network to which it normally belongs (and the corresponding prefix). The home address is a static address and, as such, it does not normally change. Still, all packets destined to the mobile host can be delivered to it, regardless of whether it operates in the home network or somewhere outside. This is made possible by the completely new features introduced with IPv6, such as stateless autoconfiguration and neighbor discovery. In addition to its home address, a mobile host gets one or more additional addresses that belong to the foreign networks where it is roaming. These are called care-of addresses. The home network has a facility that forwards any packets destined to the host when it is roaming outside. In an IPv6 environment, this task is performed by the home agent, which takes all packets destined to the home address and relays them through a tunnel. On the other hand, those packets destined to the care-of address are directly transferred to the mobile host without any special detours.
5.2.3 Coexistence of IPv4 and IPv6 #
The migration of all hosts connected to the Internet from IPv4 to IPv6 is a gradual process. Both protocols will coexist for some time to come. The coexistence on one system is guaranteed where there is a dual stack implementation of both protocols. That still leaves the question of how an IPv6 enabled host should communicate with an IPv4 host and how IPv6 packets should be transported by the current networks, which are predominantly IPv4-based. The best solutions offer tunneling and compatibility addresses (see Section 5.2.2, “Address types and structure”).
IPv6 hosts that are more or less isolated in the (worldwide) IPv4 network can communicate through tunnels: IPv6 packets are encapsulated as IPv4 packets to move them across an IPv4 network. Such a connection between two IPv4 hosts is called a tunnel. To achieve this, packets must include the IPv6 destination address (or the corresponding prefix) and the IPv4 address of the remote host at the receiving end of the tunnel. A basic tunnel can be configured manually according to an agreement between the hosts' administrators. This is also called static tunneling.
However, the configuration and maintenance of static tunnels is often too labor-intensive to use them for daily communication needs. Therefore, IPv6 provides for three different methods of dynamic tunneling:
- 6over4
IPv6 packets are automatically encapsulated as IPv4 packets and sent over an IPv4 network capable of multicasting. IPv6 is tricked into seeing the whole network (Internet) as a huge local area network (LAN). This makes it possible to determine the receiving end of the IPv4 tunnel automatically. However, this method does not scale very well and is also hampered because IP multicasting is far from widespread on the Internet. Therefore, it only provides a solution for smaller corporate or institutional networks where multicasting can be enabled. The specifications for this method are laid down in RFC 2529.
- 6to4
With this method, IPv4 addresses are automatically generated from IPv6 addresses, enabling isolated IPv6 hosts to communicate over an IPv4 network. However, several problems have been reported regarding the communication between those isolated IPv6 hosts and the Internet. The method is described in RFC 3056.
- IPv6 tunnel broker
This method relies on special servers that provide dedicated tunnels for IPv6 hosts. It is described in RFC 3053.
5.2.4 Configuring IPv6 #
To configure IPv6, you normally do not need to make any changes on the
individual workstations. IPv6 is enabled by default. To disable or enable
IPv6 on an installed system, use the YaST modprobe
-i ipv6
as
root
. It is impossible to unload
the IPv6 module after it has been loaded.
Because of the autoconfiguration concept of IPv6, the network card is assigned an address in the link-local network. Normally, no routing table management takes place on a workstation. The network routers can be queried by the workstation, using the router advertisement protocol, for what prefix and gateways should be implemented. The radvd program can be used to set up an IPv6 router. This program informs the workstations which prefix to use for the IPv6 addresses and which routers. Alternatively, use zebra/quagga for automatic configuration of both addresses and routing.
5.3 Name resolution #
DNS assists in assigning an IP address to one or more names and assigning a name to an IP address. In Linux, this conversion is usually carried out by a special type of software known as bind. The machine that takes care of this conversion is called a name server. The names make up a hierarchical system in which each name component is separated by a period. The name hierarchy is, however, independent of the IP address hierarchy described above.
Consider a complete name, such as
jupiter.example.com
, written in the
format hostname.domain
. A full
name, called a fully qualified domain name (FQDN),
consists of a host name and a domain name
(example.com
). The latter
also includes the top level domain or TLD
(com
).
TLD assignment has become quite confusing for historical reasons.
Traditionally, three-letter domain names are used in the USA. In the rest of
the world, the two-letter ISO national codes are the standard. In addition
to that, longer TLDs were introduced in 2000 that represent certain spheres
of activity (for example, .info
,
.name
,
.museum
).
In the early days of the Internet (before 1990), the file
/etc/hosts
was used to store the names of all the
machines represented over the Internet. This quickly proved to be
impractical in the face of the rapidly growing number of computers connected
to the Internet. For this reason, a decentralized database was developed to
store the host names in a widely distributed manner. This database, similar
to the name server, does not have the data pertaining to all hosts in the
Internet readily available, but can dispatch requests to other name servers.
The top of the hierarchy is occupied by root name servers. These root name servers manage the top level domains and are run by the Network Information Center (NIC). Each root name server knows about the name servers responsible for a given top level domain. Information about top level domain NICs is available at http://www.internic.net.
DNS can do more than resolve host names. The name server also knows which host is receiving e-mails for an entire domain—the mail exchanger (MX).
For your machine to resolve an IP address, it must know about at least one name server and its IP address.
The .local
top level domain is treated as link-local
domain by the resolver. DNS requests are sent as multicast DNS requests
instead of normal DNS requests. If you already use the
.local
domain in your name server configuration, you
must switch this option off in /etc/host.conf
. For
more information, see the host.conf
manual page.
To switch off MDNS during installation, use nomdns=1
as
a boot parameter.
For more information on multicast DNS, see http://www.multicastdns.org.
6 NetworkManager and wicked
#
This chapter focuses on the difference between NetworkManager and
wicked
and provides a description how to switch from wicked
to NetworkManager.
NetworkManager is a program that manages the primary network connection and other
connection interfaces. NetworkManager has been designed to be fully automatic by
default. NetworkManager is handled by systemd
and is shipped with all necessary
service unit files.
wicked
is a network management tool that provides network
configuration as a service and enables changing the network
configuration dynamically.
NetworkManager and wicked
provide similar functionality; however,
they differ in the following points:
root
privilegesIf you use NetworkManager for network setup, you can easily switch, stop, or start your network connection at any time. NetworkManager also makes it possible to change and configure wireless card connections without requiring
root
privileges.wicked
also provides some ways to switch, stop, or start the connection with or without user intervention, like user-managed devices. However, this always requiresroot
privileges to change or configure a network device.- Types of network connections
Both
wicked
and NetworkManager can handle network connections with a wireless network (with WEP, WPA-PSK, and WPA-Enterprise access) and wired networks using DHCP and static configuration. They also support connection through dial-up and VPN. With NetworkManager, you can also connect a mobile broadband (3G) modem or set up a DSL connection, which is not possible with the traditional configuration.NetworkManager tries to keep your computer connected at all times using the best connection available. If the network cable is accidentally disconnected, it tries to reconnect. NetworkManager can find the network with the best signal strength from the list of your wireless connections and automatically use it to connect. To get the same functionality with
wicked
, more configuration effort is required.- k8s integration
Some k8s plugins require NetworkManager to run and are not compatible with
wicked
.
6.1 Switching from wicked
to NetworkManager #
Even though NetworkManager and wicked
are similar in functionalities, we cannot guarantee full feature parity. The conversion of the wicked
configuration or automated switching to NetworkManager is not supported.
wicked
configuration compatibility with NetworkManager
The /etc/sysconfig/network/ifcfg-*
files are usually compatible except for some rare cases. But when you use the wicked
configuration located in /etc/wicked/*.xml
, you need to migrate the configuration manually.
To change your networking managing service from wicked
to NetworkManager, proceed as follows:
wicked
to NetworkManager #Run the following command to create a new snapshot where you perform all other changes to the system:
#
transactional-update shellInstall NetworkManager:
#
zypper in NetworkManagerRemove
wicked
from the system:#
zypper rm wicked wicked-serviceEnable the NetworkManager service:
#
systemctl enable NetworkManagerIf needed, configure the service according to your needs.
Close the
transactional-update
shell:#
exitReboot your system to switch to the new snapshot.
7 NetworkManager configuration and usage #
NetworkManager is shipped so it can run out of the box, but you might need to reconfigure or restart the tool. This chapter focuses on these tasks.
NetworkManager stores all network configuration as a connection, which is a collection
of data that describes how to create or connect to a network. These
connections are stored as files in the
/etc/NetworkManager/system-connections/
directory.
A connection is active when a particular device uses the connection. The device may have more than one connection configured, but only one can be active at a given time. The other connections can be used to fast switch from one connection to another. For example, if the active connection is not available, NetworkManager tries to connect the device to another configured connection.
To manage connections, use the nmcli
, described in
the section below.
To change how NetworkManager behaves, change or add values to the configuration file
described in Section 7.3, “The NetworkManager.conf
configuration file”.
7.1 Starting and stopping NetworkManager #
As NetworkManager is a systemd
service, you can use common systemd
commands to
start, stop, or restart NetworkManager.
To start NetworkManager:
#
systemctl start network
To restart NetworkManager:
#
systemctl restart network
To stop NetworkManager:
#
systemctl stop network
7.2 The nmcli
command #
NetworkManager provides a CLI interface to manage your connections. By using the
nmcli
interface, you can connect to a particular network,
edit a connection, edit a device, etc. The generic syntax of the
nmcli
is as follows:
#
nmcli OPTIONS SUBCOMMAND SUBCOMMAND_ARGUMENTS
where OPTIONS are described in
Section 7.2.1, “The nmcli
command options” and
SUBCOMMAND can be any of the following:
connection
enables you to configure your network connection. For details, refer to Section 7.2.2, “The
connection
subcommand”.device
For details, refer to Section 7.2.3, “The
device
subcommand”.general
shows status and permissions. For details refer to Section 7.2.4, “The
general
subcommand”.monitor
monitors activity of NetworkManager and watches for changes in the state of connectivity and devices. This subcommand does not take any arguments.
networking
queries the networking status. For details, refer to Section 7.2.5, “The
networking
subcommand”.
7.2.1 The nmcli
command options #
Besides the subcommands and their arguments, the nmcli
command can take the following options:
-a|--ask
the command will stop its run to ask for any missing arguments, for example, for a password to connect to a network.
-c|--color {yes|no|auto}
controls the color output:
yes
to enable the colors,no
to disable them, andauto
creates color output only when the standard output is directed to a terminal.-m|--mode {tabular|multiline}
switches between
table
(each line describes a single entry, columns define particular properties of the entry) andmultiline
(each entry comprises more lines, each property is on its own line).tabular
is the default value.-h|--help
prints help.
-w|--wait seconds
sets a time-out period for which to wait for NetworkManager to finish operations. Using this option is recommended for commands that might take longer to complete, for example, connection activation.
7.2.2 The connection
subcommand #
The connection
command enables you to manage connections
or view any information about particular connections. The nmcli
connection
provides the following commands to manage your network
connections:
show
to list connections:
#
nmcli connection showYou can also use this command to show details about a specified connection:
#
nmcli connection show CONNECTION_IDwhere CONNECTION_ID is any of the identifiers: a connection name, UUID, or a path
up
to activate the provided connection. Use the command to reload a connection. Also run this command after you perform any change to the connection.
#
nmcli connection up [--active] [CONNECTION_ID]When
--active
is specified, only the active profiles are displayed. The default is to display both active connections and static configuration.down
to deactivate a connection.
#
nmcli connection down CONNECTION_IDwhere: CONNECTION_ID is any of the identifiers: a connection name, UUID, or a path
If you deactivate the connection, it will not reconnect later even if it has the
autoconnect
flag.modify
to change or delete a property of a connection.
#
nmcli connection modify CONNECTION_ID SETTING.PROPERTY PROPERTY_VALUEwhere:
CONNECTION_ID is any of the identifiers: a connection name, UUID, or a path
SETTING.PROPERTY is the name of the property, for example,
ipv4.addresses
PROPERTY_VALUE is the desired value of SETTING.PROPERTY
The following example deactivates the
autoconnect
option on theethernet1
connection:#
nmcli connection modify ethernet1 connection.autoconnect noadd
to add a connection with the provided details. The command syntax is similar to the
modify
command:#
nmcli connection add CONNECTION_ID save YES|NO SETTING.PROPERTY PROPERTY_VALUEYou should at least specify a
connection.type
or usetype
. The following example adds an Ethernet connection tied to theeth0
interface with DHCP, and disables the connection'sautoconnect
flag:#
nmcli connection add type ethernet autoconnect no ifname eth0edit
to edit an existing connection using an interactive editor.
#
nmcli connection edit CONNECTION_IDclone
to clone an already existing connection. The minimal syntax follows:
#
nmcli connection clone CONNECTION_ID NEW_NAMEwhere CONNECTION_ID is the connection to be cloned.
delete
to delete an existing connection:
#
nmcli connection delete CONNECTION_IDmonitor
to monitor the provided connection. Each time the connection changes, NetworkManager prints a line.
#
nmcli connection monitor CONNECTION_IDreload
to reload all connection files from the disk. As NetworkManager does not monitor changes performed to the connection files, you need to use this command whenever you make changes to the files. This command does not take any further subcommands.
load
to load/reload a particular connection file, run:
#
nmcli connection load CONNECTION_FILE
7.2.3 The device
subcommand #
The device
subcommand enables you to show and manage
network interfaces. The nmcli device
command recognizes
the following commands:
status
to print the status of all devices.
#
nmcli device statusshow
shows detailed information about a device. If no device is specified, all devices are displayed.
#
mcli device show [DEVICE_NAME]connect
to connect a device. NetworkManager tries to find a suitable connection that will be activated. If there is no compatible connection, a new profile is created.
#
nmcli device connect DEVICE_NAMEmodify
performs temporary changes to the configuration that is active on the particular device. The changes are not stored in the connection profile.
#
nmcli device modify DEVICE_NAME [+|-] SETTING.PROPERTY VALUEFor possible SETTING.PROPERTY values, refer to nm-settings-nmcli(5).
The example below starts the IPv4 shared connection sharing on the device
con1
.#
nmcli dev modify con1 ipv4.method shareddisconnect
disconnects a device and prevents the device from automatically activating further connections without manual intervention.
#
nmcli device disconnect DEVICE_NAMEdelete
to delete the interface from the system. You can use the command to delete only software devices like bonds and bridges. You cannot delete hardware devices with this command.
#
nmcli device DEVICE_NAMEwifi
lists all available access points.
#
nmcli device wifiwifi connect
connects to a Wi-Fi network specified by its SSID or BSSID. The command takes the following options:
password
- password for secured networksifname
- interface that will be used for activationname
- you can give the connection a name
#
nmcli device wifi connect SSID [password PASSWORD_VALUE] [ifname INTERFACE_NAME]To connect to a Wi-Fi GUESTWiFi with a password
pass$word2#@@
, run:#
nmcli device wifi connect GUESTWiFi password pass$word2#@@
7.2.4 The general
subcommand #
You can use this command to view NetworkManager status and permissions, and change the
host name and logging level. The nmcli general
recognizes the following commands:
status
displays the overall status of NetworkManager. Whenever you do not specify a command to the
nmcli general
command, status is used by default.#
nmcli general statushostname
if you do not provide a new host name as an argument, the current host name is displayed. If you specify a new host name, the value will be used to set a new value.
#
nmcli general hostname [HOSTNAME]For example, to set
MyHostname
, run:#
nmcli general hostname MyHostnamepermissions
shows your permission for NetworkManager operations like enabling or disabling networking, modifying connections, etc.
#
nmcli general permissionslogging
shows and changes NetworkManager logging levels and domains. Without any arguments, the command displays current logging levels and domains.
#
nmcli general logging [level LEVEL domains DOMAIN]LEVEL is any of the values:
OFF
,ERR
,WARN
,INFO
,DEBUG
, orTRACE
.DOMAIN is a list of values that can be as follows:
PLATFORM, RFKILL, ETHER, WIFI, BT, MB, DHCP4, DHCP6, PPP, WIFI_SCAN, IP4, IP6, AUTOIP4, DNS, VPN, SHARING, SUPPLICANT, AGENTS, SETTINGS, SUSPEND, CORE, DEVICE, OLPC, WIMAX, INFINIBAND, FIREWALL, ADSL, BOND, VLAN, BRIDGE, DBUS_PROPS, TEAM, CONCHECK, DCB, DISPATCH, AUDIT, SYSTEMD, VPN_PLUGIN, PROXY
.
7.2.5 The networking
subcommand #
The subcommand enables you to query the status of the network. Also,
by using this command, you can enable or disable networking. The
nmcli networking
command takes the following
commands:
on/off
enables or disables networking. The
off
command deactivates all interfaces managed by NetworkManager.#
nmcli networking on- connectivity
displays the network connectivity state. If
check
is used, NetworkManager performs a new check of the state. Otherwise, the last detected state is displayed.#
nmcli networking connectivityPossible states are the following:
none - the host is not connected to any network.
portal - the host is behind a captive portal and cannot reach the full Internet.
limited - the host is connected to a network, but it has no access to the Internet.
full - the host is connected to a network and has full access to the Internet.
unknown - NetworkManager could not determine the network state.
7.3 The NetworkManager.conf
configuration file #
The main configuration file for the NetworkManager is
/etc/NetworkManager/NetworkManager.conf
. This file can
be used to configure the behavior of NetworkManager.
The file consists of sections of key-value pairs. Each key-value pair must
belong to a section. A section starts with a name enclosed in
[]. Lines beginning with a # are
considered comments. The minimal configuration needs to include the
[main]
section with the plugins
value:
[main] plugins=keyfile
The keyfile
plugin supports all the connection types and
capabilities of NetworkManager.
The default configuration file contains the connectivity
section that specifies the URI to check the network connection.
On SLE Micro, you can also use other sections. For details, refer to networkmanager.conf(5) .
Part III Monitoring and debugging #
- 8 Health checker
Health checker is a program delivered with SLE Micro that checks whether services are running properly during booting of your system.
- 9
toolbox
for SLE Micro debugging This chapter describes the usage and purpose of the
toolbox
utility.- 10 Monitoring performance
For performance monitoring purposes, SLE Micro provides a container image that enables you to run the Performance Co-Pilot (PCP) analysis toolkit in a container. The toolkit comprises tools for gathering and processing performance information collected either in real time or from PCP archive logs.
8 Health checker #
Health checker is a program delivered with SLE Micro that checks whether services are running properly during booting of your system.
During the boot process, systemd
calls Health checker,
which in turn calls its plugins. Each plugin checks a particular service or
condition. If each check passes, a status file
(/var/lib/misc/health-check.state
) is created. The
status file marks the current root file system as correct.
If any of the health checker plugins reports an error, the action taken depends on a particular condition, as described below:
- The snapshot is booted for the first time.
If the current snapshot is different from the last one that worked properly, an automatic rollback to the last working snapshot is performed. This means that the last change performed to the file system broke the snapshot.
- The snapshot has already booted correctly in the past.
There could be just a temporary problem, and the system is rebooted automatically.
- The reboot of a previously correctly booted snapshot has failed.
If there was already a problem during boot and automatic reboot has been triggered, but the problem still persists, then the system is kept running to enable to the administrator to fix the problem. The services that are tested by the health checker plugins are stopped if possible.
8.1 Adding custom plugins #
Health checker supports the addition of your own plugins to check services during the boot process. Each plugin is a bash script that must fulfill the following requirements:
Plugins are located within a specific directory—
/usr/libexec/health-checker
The service that will be checked by the particular plugin must be defined in the
Unit
section of the/usr/lib/systemd/system/health-checker.service
file. For example, theetcd
service is defined as follows:[Unit] ... After=etcd.service ...
Each plugin must have functions called
run.checks
andstop_services
defined. Therun.checks
function checks whether a particular service has started properly. Bear in mind that service that has not been enabled by systemd, should be ignored. The functionstop_services
is called to stop the particular service in case the service has not been started properly. You can use the plugin template for your reference.
9 toolbox
for SLE Micro debugging #
This chapter describes the usage and purpose of the
toolbox
utility.
SLE Micro uses the transactional-update
command to apply
changes to the system, but the changes are applied only after reboot. That
solution has several benefits, but it also has some disadvantages. If you
need to debug your system and install a new tool, the tool will be available
only after reboot. Therefore you are not able to debug the currently running
system. For this reason a utility called toolbox
has been
developed.
toolbox
is a small script that pulls a container image and
runs a privileged container based on that image. In the toolbox container you
can install any tool you want with zypper
and then use the
tool without rebooting your system.
To start the toolbox
container, run the following:
#
/usr/bin/toolbox
If the script completes successfully, you will see the
toolbox
container prompt.
toolbox
image
You can also use Podman or Cockpit to pull the toolbox
image and start a container based on that image.
10 Monitoring performance #
For performance monitoring purposes, SLE Micro provides a container image that enables you to run the Performance Co-Pilot (PCP) analysis toolkit in a container. The toolkit comprises tools for gathering and processing performance information collected either in real time or from PCP archive logs.
The performance data are collected by performance metrics domain
agents and passed to the pmcd daemon. The
daemon coordinates the gathering and exporting of performance statistics in
response to requests from the PCP monitoring tools.
pmlogger
is then used to log the metrics. For details,
refer to the
PCP
documentation.
10.1 Getting the PCP container image #
The PCP container image is based on the BCI-Init
container that utilizes systemd
used to manage the PCP services.
You can pull the container image using podman or from the Cockpit web management console. To pull the image by using podman, run the following command:
#
podman pull registry.suse.com/suse/pcp:latest
To get the container image using Cockpit, go to pcp. Then select the image from the
registry.suse.com
for SLE 15 SP4 and download it.
10.2 Running the PCP container #
The following command shows minimal options that you need to use to run a PCP container:
#
podman run -d \
--systemd always \
-p HOST_IP:HOST_PORT:CONTAINER_PORT \
-v HOST_DIR:/var/log/pcp/pmlogger \
PCP_CONTAINER_IMAGE
where the options have the following meaning:
-d
The container will run in a detached mode without tty.
--systemd always
Runs the container in the
systemd
mode. All services needed to run in the PCP container will be started automatically bysystemd
in the container.--privileged
The container runs with extended privileges. Use this option if your system has SELinux enabled, otherwise the collected metrics will be incomplete.
-v HOST_DIR:/var/log/pcp/pmlogger
Creates a bind mount so that
pmlogger
archives are written to the HOST_DIR on the host. By default,pmlogger
stores the collected metrics in/var/log/pcp/pmlogger
.- PCP_CONTAINER_IMAGE
Is the downloaded PCP container image.
Other useful options of the podman run
command follow:
-p HOST_IP:HOST_PORT:CONTAINER_PORT
Publishes ports of the container by mapping a container port onto a host port. If you do not specify HOST_IP, the ports will be mapped on the local host. If you omit the HOST_PORT value, a random port number will be used. By default, the
pmcd
daemon listens and exposes the PMAPI to receive metrics on the port 44321, so it is recommended to map this port on the same port number on the host. Thepmproxy
daemon listens on and exposes the REST PMWEBAPI to access metrics on the 44322 port by default, so it is recommended to map this port on the same host port number.--net host
The container uses the host's network. Use this option if you want to collect metrics from the host's network interfaces.
-e
The option enables you to set the following environment variables:
- PCP_SERVICES
Is a comma-separated list of services to start by
systemd
in the container.Default services are:
pmcd
,pmie
,pmlogger
,pmproxy
.You can use this variable, if you want to run a container with a list of services that is different from the default one, for example, only with
pmlogger
:#
podman run -d \ --name pmlogger \ --systemd always \ -e PCP_SERVICES=pmlogger \ -v pcp-archives:/var/log/pcp/pmlogger \ registry.suse.com/suse/pcp:latest- HOST_MOUNT
Is a path inside the container to the bind mount of the host's root file system. The default value is not set.
- REDIS_SERVERS
Specifies a connection to a Redis server. In a non-clustered setup, provide a comma-separated list of host specs. In a clustered setup, provide any individual cluster host, other hosts in the cluster are discovered automatically. The default value is:
localhost:6379
.
If you need to use a different configuration to the one provided by the environment variables, proceed as described in Section 10.3, “Configuring PCP services”.
10.3 Configuring PCP services #
All services that run inside the PCP container have a default configuration that might not suit your needs. If you need a custom configuration that cannot be covered by the environment variables described above, create configuration files for the PCP services and pass them to the PCP using a bind mount as follows:
#
podman run -d \
--name CONTAINER_NAME \
--systemd always \
-v $HOST_CONFIG:CONTAINER_CONFIG_PATH:z \
-v HOST_LOGS_PATH:/var/log/pcp/pmlogger \
registry.suse.com/suse/pcp:latest
Where:
- CONTAINER_NAME
Is an optional container name.
- HOST_CONFIG
Is an absolute path to the config you created on the host machine. You can choose any file name you want.
- CONTAINER_CONFIG_PATH
Is an absolute path to a particular configuration file inside the container. Each available configuration file is described in the corresponding sections further.
- HOST_LOGS_PATH
Is a directory that should be a bind mount to the container logs.
For example, a container called pcp
, with the
configuration file pmcd
on the host machine and the
pcp-archives
directory for logs on the host machine, is
run by the following command:
#
podman run -d \
--name pcp \
--systemd always \
-v $(pwd)/pcp-archives:/var/log/pcp/pmlogger \
-v $(pwd)/pmcd:/etc/sysconfig/pmcd \
registry.suse.com/suse/pcp:latest
10.3.1 Custom pmcd
daemon configuration #
The pmcd
daemon configuration is stored in the
/etc/sysconfig/pmcd
file. The file stores environment
variables that modify the behavior of the pmcd
daemon.
10.3.1.1 The /etc/sysconfig/pmcd
file #
You can add the following variables to the file to configure the
pmcd
daemon:
- PMCD_LOCAL
Defines whether the remote host can connect to the
pmcd
daemon. If set to 0, remote connections to the daemon are allowed. If set to 1, the daemon listens only on the local host. The default value is 0.- PMCD_MAXPENDING
Defines the maximum count of pending connections to the agent. The default value is 5.
- PMCD_ROOT_AGENT
If the
pmdaroot
is enabled (the value is set to 1), adding a new PDMA does not trigger restarting of other PMDAs. Ifpmdaroot
is not enabled,pmcd
will require to restart all PMDAs when a new PMDA is added. The default value is 1.- PMCD_RESTART_AGENTS
If set to 1, the
pmcd
daemon tries to restart any exited PMDA. Enable this option only if you have enabledpmdaroot
, aspmcd
itself does not have privileges to restart PMDA.- PMCD_WAIT_TIMEOUT
Defines the maximum time in seconds
pmcd
can wait to accept a connection. After this time, the connection is reported as failed. The default value is 60.- PCP_NSS_INIT_MODE
Defines the mode in which
pmcd
initializes the NSS certificate database when secured connections are used. The default value isreadonly
. You can set the mode toreadwrite
, but if the initialization fails, the default value is used as a fallback.
An example follows:
PMCD_LOCAL=0 PMCD_MAXPENDING=5 PMCD_ROOT_AGENT=1 PMCD_RESTART_AGENTS=1 PMCD_WAIT_TIMEOUT=70 PCP_NSS_INIT_MODE=readwrite
10.3.2 Custom pmlogger
configuration #
The custom configuration for the pmlogger
is stored in
the following configuration files:
/etc/sysconfig/pmlogger
/etc/pcp/pmlogger/control.d/local
10.3.2.1 The /etc/sysconfig/pmlogger
file #
You can use the following attributes to configure the
pmlogger
:
- PMLOGGER_LOCAL
Defines whether
pmlogger
allows connections from remote hosts. If set to 1,pmlogger
allows connections from local host only.- PMLOGGER_MAXPENDING
Defines the maximum count of pending connections. The default value is 5.
- PMLOGGER_INTERVAL
Defines the default sampling interval
pmlogger
uses. The default value is 60 s. Keep in mind that this value can be overridden by thepmlogger
command line.- PMLOGGER_CHECK_SKIP_LOGCONF
Setting this option to yes disables the regeneration and checking of the
pmlogger
configuration if the configurationpmlogger
comes frompmlogconf
. The default behavior is to regenerate configuration files and check for changes every timepmlogger
is started.
An example follows:
PMLOGGER_LOCAL=1 PMLOGGER_MAXPENDING=5 PMLOGGER_INTERVAL=10 PMLOGGER_CHECK_SKIP_LOGCONF=yes
10.3.2.2 The /etc/pcp/pmlogger/control.d/local
file #
The file /etc/pcp/pmlogger/control.d/local
stores
specifications of the host, which metrics should be logged, the logging
frequency (default is 24 hours), and pmlogger
options.
For example:
# === VARIABLE ASSIGNMENTS === # # DO NOT REMOVE OR EDIT THE FOLLOWING LINE $version=1.1 # Uncomment one of the lines below to enable/disable compression behaviour # that is different to the pmlogger_daily default. # Value is days before compressing archives, 0 is immediate compression, # "never" or "forever" suppresses compression. # #$PCP_COMPRESSAFTER=0 #$PCP_COMPRESSAFTER=3 #$PCP_COMPRESSAFTER=never # === LOGGER CONTROL SPECIFICATIONS === # #Host P? S? directory args # local primary logger LOCALHOSTNAME y n PCP_ARCHIVE_DIR/LOCALHOSTNAME -r -T24h10m -c config.default -v 100Mb
If you run the pmlogger
in a container on a different
machine than the one that runs the pmcd
(a client),
change the following line to point to the client:
# local primary logger CLIENT_HOSTNAME y n PCP_ARCHIVE_DIR/CLIENT_HOSTNAME -r -T24h10m -c config.default -v 100Mb
For example, for the slemicro_1
host name, the line
should look as follows:
# local primary logger slemicro_1 y n PCP_ARCHIVE_DIR/slemicro_1 -r -T24h10m -c config.default -v 100Mb
10.4 Starting the PCP container automatically on boot #
After you run the PCP container, you can configure systemd
to start the
container on boot. To do so, follow the procedure below:
Create a unit file for the container by using the
podman generate systemd
command:#
podman generate systemd --name CONTAINER_NAME > /etc/systemd/system/container-CONTAINER_NAME.servicewhere CONTAINER_NAME is the name of the PCP container you used when running the container from the container image.
Enable the service in
systemd
:#
systemctl enable container-CONTAINER_NAME
10.5 Metrics management #
10.5.1 Listing available performance metrics #
From within the container, you can use the command
pminfo
to list metrics. For example, to list all
available performance metrics, run:
#
pminfo
You can list a group of related metrics by specifying the metrics prefix:
#
pminfo METRIC_PREFIX
For example, to list all metrics related to kernel, use:
#
pminfo disk
disk.dev.r_await
disk.dm.await
disk.dm.r_await
disk.md.await
disk.md.r_await
...
You can also specify additional strings to narrow down the list of metrics, for example:
#
piminfo disk.dev
disk.dev.read
disk.dev.write
disk.dev.total
disk.dev.blkread
disk.dev.blkwrite
disk.dev.blktotal
...
To get online help text of a particular metric, use the -t
option followed by the metric, for example:
#
pminfo -t kernel.cpu.util.user
kernel.cpu.util.user [percentage of user time across all CPUs, including guest CPU time]
To display a description text of a particular metric, use the
-T
option followed by the metric, for example:
#
pminfo -T kernel.cpu.util.user
Help:
percentage of user time across all CPUs, including guest CPU time
10.5.2 Checking local metrics #
After you start the PCP container, you can verify that metrics are being recorded properly by running the following command inside the container:
#
pcp
Performance Co-Pilot configuration on localhost:
platform: Linux localhost 5.3.18-150300.59.68-default #1 SMP Wed May 4 11:29:09 UTC 2022 (ea30951) x86_64
hardware: 1 cpu, 1 disk, 1 node, 1726MB RAM
timezone: UTC
services: pmcd pmproxy
pmcd: Version 5.2.2-1, 9 agents, 4 clients
pmda: root pmcd proc pmproxy xfs linux mmv kvm jbd2
pmlogger: primary logger: /var/log/pcp/pmlogger/localhost/20220607.09.24
pmie: primary engine: /var/log/pcp/pmie/localhost/pmie.log
Now check if the logs are written to a proper destination:
#
ls PATH_TO_PMLOGGER_LOGS
where PATH_TO_PMLOGGER_LOGS should be
/var/log/pcp/pmlogger/localhost/
in this case.
10.5.3 Recording metrics from remote systems #
You can deploy collector containers that collect metrics from different
remote systems than the ones where the pmlogger
containers are running. Each remote collector system needs the
pmcd
daemon and a set of pmda. To
deploy several collectors with a centralized monitoring system, proceed as
follows.
On each system you want to collect metrics from (clients), run a container with the
pmcd
daemon:#
podman run -d \ --name pcp-pmcd \ --privileged \ --net host \ --systemd always \ -e PCP_SERVICES=pmcd \ -e HOST_MOUNT=/host \ -v /:/host:ro,rslave \ registry.suse.com/suse/pcp:latestOn the monitoring system, create a
pmlogger
configuration file for each clientcontrol.CLIENT
with the following content:$version=1.1 CLIENT_HOSTNAME n n PCP_ARCHIVE_DIR/CLIENT -N -r -T24h10m -c config.default -v 100Mb
Keep in mind that the CLIENT_HOSTNAME must be resolvable in DNS. You can use IP addresses or fully qualified domain names (FQDN) instead.
On the monitoring system, create a directory for each client to store the recorded logs:
#
mkdir /root/pcp-archives/CLIENTFor example, for
slemicro_1
:#
mkdir /root/pcp-archives/slemicro_1On the monitoring system, run a container with
pmlogger
for each client:#
podman run -d \ --name pcp-pmlogger-CLIENT \ --systemd always \ -e PCP_SERVICES=pmlogger \ -v /root/pcp-archives/CLIENT:/var/log/pcp/pmlogger:z \ -v $(pwd)/control.CLIENT:/etc/pcp/pmlogger/control.d/local:z \ registry.suse.com/suse/pcp:latestFor example, for a client called
slemicro_1
:#
podman run -d \ --name pcp-pmlogger-slemicro_1 \ --systemd always \ -e PCP_SERVICES=pmlogger \ -v /root/pcp-archives:/var/log/pcp/pmlogger:z \ -v $(pwd)/control.slemicro_1:/etc/pcp/pmlogger/control.d/local:z \ registry.suse.com/suse/pcp:latestNoteThe second bind mount points to the configuration file created in Step 2 and replaces the default
pmlogger
configuration. If you do not create this bind mount,pmlogger
uses the default/etc/pcp/pmlogger/control.d/local
file and logging from clients fails as the default configuration points to a local host. For details about the configuration file, refer to Section 10.3.2.2, “The/etc/pcp/pmlogger/control.d/local
file”.To check if the log collection is working properly, run:
#
ls -l pcp-archives/CLIENT/CLIENTFor example:
#
ls -l pcp-archives/slemicro_1/slemicro_1 total 1076 -rw-r--r--. 1 systemd-network systemd-network 876372 Jun 8 11:24 20220608.10.58.0 -rw-r--r--. 1 systemd-network systemd-network 312 Jun 8 11:22 20220608.10.58.index -rw-r--r--. 1 systemd-network systemd-network 184486 Jun 8 10:58 20220608.10.58.meta -rw-r--r--. 1 systemd-network systemd-network 246 Jun 8 10:58 Latest -rw-r--r--. 1 systemd-network systemd-network 24595 Jun 8 10:58 pmlogger.log
Part IV Troubleshooting #
- 11 Gathering system information for support
In case of problems, a detailed system report may be created with the
supportconfig
command-line tool. The tool will collect information about the system, such as the current kernel version, hardware, installed packages, partition setup, and much more. The result is a TAR archive of files. After opening a Service Request (SR), you can upload the TAR archive to Global Technical Support. It will help you to locate the reported issue and solve the problem.You can analyze the
supportconfig
output for known issues to help resolve problems faster.
11 Gathering system information for support #
In case of problems, a detailed system report may be created with the
supportconfig
command-line tool. The tool will
collect information about the system, such as the current kernel
version, hardware, installed packages, partition setup, and much more.
The result is a TAR archive of files. After opening a Service Request
(SR), you can upload the TAR archive to Global Technical Support. It
will help you to locate the reported issue and solve the problem.
You can analyze the supportconfig
output for known
issues to help resolve problems faster.
11.1 Collecting system information with supportconfig
#
To create a TAR archive with detailed system information that you can
hand over to Global Technical Support, use the command
supportconfig
. The command-line tool is provided by
the package supportutils
which is installed by
default.
Depending on which packages are installed on your system, some of these
packages integrate supportconfig
plug-ins. When
supportconfig
is executed, all plug-ins are executed
as well, creating one or more result files for the archive. This has the
benefit that the only topics checked are those that contain a specific
plug-in for them. supportconfig
plug-ins are stored in
the directory /usr/lib/supportconfig/plugins/
.
The following procedure shows how to create a Supportconfig archive, but without submitting it to support directly. For uploading it, you need to run the command with certain options as described in Procedure 11.1, “Submitting information to support from command line”.
Run
supportconfig
asroot
. Usually, it is enough to run this tool without any options. Some options are very common and are displayed in the following list:-E MAIL
,-N NAME
,-O COMPANY
,-P PHONE
Sets your contact data: e-mail address (
-E
), company name (-O
), your name (-N
), and your phone number (-P
).-i KEYWORDS
,-F
Limits the features to check. The placeholder KEYWORDS is a comma-separated list of case-sensitive keywords. Get a list of all keywords with
supportconfig -F
.
Wait for the tool to complete the operation.
The default archive location is
/var/log
, with the file name format beingscc_HOST_DATE_TIME.txz
11.1.1 Understanding the output of supportconfig
#
If you run supportconfig
, the script gives you a
summary of what it did.
Support Utilities - Supportconfig Script Version: 3.1.11-46.2 Library Version: 3.1.11-29.6 Script Date: 2022 10 18 [...] Gathering system information Data Directory: /var/log/scc_d251_180201_1525 1 Basic Server Health Check... Done 2 RPM Database... Done 2 Basic Environment... Done 2 System Modules... Done 2 [...] File System List... Skipped 3 [...] Command History... Excluded 4 [...] Supportconfig Plugins: 1 5 Plugin: pstree... Done [...] Creating Tar Ball ==[ DONE ]=================================================================== Log file tar ball: /var/log/scc_d251_180201_1525.txz 6 Log file size: 732K Log file md5sum: bf23e0e15e9382c49f92cbce46000d8b =============================================================================
The temporary data directory to store the results. This directory is archived as a tar file, see 6. | |
The feature was enabled (either by default or selected manually) and executed successfully. The result is stored in a file (see Table 11.1, “Comparison of features and file names in the TAR archive”). | |
The feature was skipped because some files of one or more RPM packages were changed. | |
The feature was excluded because it was deselected via the
| |
The script found one plug-in and executes the plug-in
| |
The tar file name of the archive, compressed with
|
11.1.2 Common supportconfig options #
The supportconfig
utility is usually called without
any options. Display a list of all options with
supportconfig
-h
. The following
list gives a brief overview of some common use cases:
- Reducing the amount of the information being gathered
Use the minimal option (
-m
):#
supportconfig -m- Limiting the information to a specific topic
If you have already localized a problem that relates to a specific area or feature set only, you should limit the collected information to the specific area for the next
supportconfig
run. For example, you have detected problems with LVM and want to test a recent change that you introduced to the LVM configuration. In this case, it makes sense to gather the minimum Supportconfig information around LVM only:#
supportconfig -i LVMAdditional keywords can be separated with commas. For example, an additional disk test:
#
supportconfig -i LVM,DISKFor a complete list of feature keywords that you can use for limiting the collected information to a specific area, run:
#
supportconfig -F- Including additional contact information in the output:
#
supportconfig -E tux@example.org -N "Tux Penguin" -O "Penguin Inc." ...(all in one line)
- Collecting already rotated log files
#
supportconfig -lThis is especially useful in high-logging environments or after a kernel crash when syslog rotates the log files after a reboot.
11.1.3 Overview of the archive content #
The TAR archive contains all the results from the features. Depending
on what you have selected (all or only a small set), the archive can
contain more or fewer files. The set of features can be limited using
the -i
option (see
Section 11.1.2, “Common supportconfig options”).
To list the contents of the archive, use the following
tar
command:
#
tar
xf /var/log/scc_earth_180131_1545.txz
The following file names are always available inside the TAR archive:
basic-environment.txt
Contains the date when this script was executed and system information like version of the distribution, hypervisor information, and more.
basic-health-check.txt
Contains some basic health checks like uptime, virtual memory statistics, free memory and hard disk, checks for zombie processes, and more.
hardware.txt
Contains basic hardware checks like information about the CPU architecture, list of all connected hardware, interrupts, I/O ports, kernel boot messages, and more.
messages.txt
Contains log messages from the system journal.
rpm.txt
Contains a list of all installed RPM packages, their names and versions and where they come from.
summary.xml
Contains information in XML format, such as distribution, version and product-specific fragments.
supportconfig.txt
Contains information about the
supportconfig
script itself.y2log.txt
Contains YaST-specific information like specific packages, configuration files and log files.
Table 11.1, “Comparison of features and file names in the TAR archive” lists all available features and their file names.
Feature | File name |
---|---|
APPARMOR | security-apparmor.txt
|
AUDIT | security-audit.txt
|
AUTOFS | fs-autofs.txt
|
BOOT | boot.txt
|
BTRFS | fs-btrfs.txt
|
DAEMONS | systemd.txt
|
CIMOM | cimom.txt
|
CRASH | crash.txt
|
CRON | cron.txt
|
DHCP | dhcp.txt
|
DISK | fs-diskio.txt
|
DNS | dns.txt
|
DOCKER | docker.txt
|
DRBD | drbd.txt
|
ENV | env.txt
|
ETC | etc.txt
|
HISTORY | shell_history.txt
|
ISCSI | fs-iscsi.txt
|
LDAP | ldap.txt
|
LIVEPATCH | kernel-livepatch.txt
|
LVM | lvm.txt
|
MEM | memory.txt
|
MOD | modules.txt
|
MPIO | mpio.txt
|
NET | network-*.txt
|
NFS | nfs.txt
|
NTP | ntp.txt
|
NVME | nvme.txt
|
OCFS2 | ocfs2.txt
|
PAM | pam.txt
|
PODMAN | podman.txt
|
print.txt
| |
PROC | proc.txt
|
SAR | sar.txt
|
SLERT | slert.txt
|
SLP | slp.txt
|
SMT | smt.txt
|
SMART | fs-smartmon.txt
|
SMB | samba.txt
|
SRAID | fs-softraid.txt
|
SSH | ssh.txt
|
SSSD | sssd.txt
|
SYSCONFIG | sysconfig.txt
|
SYSFS | sysfs.txt
|
TRANSACTIONAL | transactional-update.txt
|
TUNED | tuned.txt
|
UDEV | udev.txt
|
UFILES | fs-files-additional.txt
|
UP | updates.txt
|
WEB | web.txt
|
11.2 Submitting information to Global Technical Support #
After you have created the archive using the
supportconfig
tool, you can submit the archive to
SUSE.
11.2.1 Creating a service request number #
Before handing over the supportconfig
data to Global
Technical Support, you need to generate a service request number first.
You will need it to upload the archive to support.
To create a service request, go to https://scc.suse.com/support/requests and follow the instructions on the screen. Write down the service request number.
SUSE treats system reports as confidential data. For details about our privacy commitment, see https://www.suse.com/company/policies/privacy/.
11.2.2 Upload targets #
After having created a service request number, you can upload your Supportconfig archives to Global Technical Support. In the examples below, the 12345678901 serves as a placeholder for your service request number. Replace the placeholder with the service request number you created in Section 11.2.1, “Creating a service request number”.
The following procedure assumes that you have already created a Supportconfig archive but have not uploaded it yet.
Servers with Internet connectivity:
To use the default upload target https://support-ftp.us.suse.com/incoming/upload.php?file={tarball}, run:
>
sudo
supportconfig -ur 12345678901For the FTPS upload target ftps://support-ftp.us.suse.com, use the following command:
>
sudo
supportconfig -ar 12345678901To use a different upload target, for example, for the EMEA area, use the
-U
followed by the particular URL, either https://support-ftp.emea.suse.com/incoming/upload.php?file={tarball} or ftps://support-ftp.emea.suse.com/incoming/>
sudo
supportconfig -r 12345678901 -U https://support-ftp.emea.suse.com/incoming
Servers without Internet connectivity:
Run the following:
>
sudo
supportconfig -r 12345678901Manually upload the
/var/log/scc_SR12345678901*txz
archive to one of our servers. The selection of a server depends on your location in the world:North America: HTTPS https://support-ftp.us.suse.com/incoming/upload.php?file={tarball}, FTPS ftps://support-ftp.us.suse.com/incoming/
EMEA, Europe, the Middle East, and Africa: FTP https://support-ftp.emea.suse.com/incoming/upload.php?file={tarball}, FTPS ftps://support-ftp.emea.suse.com/incoming/
After the TAR archive arrives in the incoming directory of our FTP server, it becomes automatically attached to your service request.
11.3 Gathering information during the installation #
When performing the manual installation, supportconfig
is not available. However, you can collect log files from YaST by using
save_y2logs
. This command will create a
.tar.xz
archive in the directory
/tmp
.
11.4 Support of kernel modules #
An important requirement for every enterprise operating system is the
level of support you receive for your environment. Kernel modules are the
most relevant connector between hardware (“controllers”) and
the operating system. Every kernel module in SLE Micro has a
supported
flag that can take three possible values:
“yes,” thus
supported
“external,” thus
supported
(empty, not set), thus
unsupported
The following rules apply:
All modules of a self-recompiled kernel are by default marked as unsupported.
Kernel modules supported by SUSE partners and delivered using
SUSE SolidDriver Program
are marked “external.”If the
supported
flag is not set, loading this module will taint the kernel. Tainted kernels are not supported.Kernel modules not provided under a license compatible to the license of the Linux kernel will also taint the kernel. For details, see the state of
/proc/sys/kernel/tainted
.
11.4.1 Technical background #
Linux kernel: The value of
/proc/sys/kernel/unsupported
defaults to2
, which means that no syslog warning is generated when unsupported modules are loaded. This default is used in the installer and in the installed system.modprobe
: Themodprobe
utility for checking module dependencies and loading modules appropriately checks for the value of thesupported
flag. If the value is “yes” or “external,” the module will be loaded, otherwise it will not. For information on how to override this behavior, see Section 11.4.2, “Working with unsupported modules”.Note: SupportSUSE does not generally support the removal of storage modules via
modprobe -r
.
11.4.2 Working with unsupported modules #
While general supportability is important, situations can occur where loading an unsupported module is required. For example, for testing or debugging purposes, or if your hardware vendor provides a hotfix.
To override the default, copy
/lib/modprobe.d/10-unsupported-modules.conf
to/etc/modprobe.d/10-unsupported-modules.conf
and change the value of the variableallow_unsupported_modules
from0
to1
. Do not edit/lib/modprobe.d/10-unsupported-modules.conf
directly; any changes will be overwritten whenever the suse-module-tools package is updated.If an unsupported module is needed in the initrd, do not forget to run
transactional-update initrd
to update the initrd.If you only want to try loading a module once, you can use the
--allow-unsupported-modules
option withmodprobe
. For more information, see the comments in/lib/modprobe.d/10-unsupported-modules.conf
and themodprobe
help.To enforce the loading of unsupported modules during boot and afterward, use the kernel command-line option
oem-modules
. While installing and initializing thesuse-module-tools
package, the kernel flagTAINT_NO_SUPPORT
(/proc/sys/kernel/tainted
) will be evaluated. If the kernel is already tainted,allow_unsupported_modules
will be enabled. This will prevent unsupported modules from failing in the system being installed. If no unsupported modules are present during installation and the other special kernel command-line option (oem-modules=1
) is not used, the default is still to disallow unsupported modules.
Remember that loading and running unsupported modules will make the kernel and the whole system unsupported by SUSE.
A GNU licenses #
This appendix contains the GNU Free Documentation License version 1.2.
GNU Free Documentation License #
Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc. 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
0. PREAMBLE #
The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or non-commercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.
We have designed this License to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.
1. APPLICABILITY AND DEFINITIONS #
This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.
A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.
The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.
The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.
A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements", "Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section when you modify the Document means that it remains a section "Entitled XYZ" according to this definition.
The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.
2. VERBATIM COPYING #
You may copy and distribute the Document in any medium, either commercially or non-commercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and you may publicly display copies.
3. COPYING IN QUANTITY #
If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.
If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.
4. MODIFICATIONS #
You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:
Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
State on the Title page the name of the publisher of the Modified Version, as the publisher.
Preserve all the copyright notices of the Document.
Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
Include an unaltered copy of this License.
Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
Delete any section Entitled "Endorsements". Such a section may not be included in the Modified Version.
Do not retitle any existing section to be Entitled "Endorsements" or to conflict in title with any Invariant Section.
Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.
You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.
5. COMBINING DOCUMENTS #
You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements".
6. COLLECTIONS OF DOCUMENTS #
You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.
7. AGGREGATION WITH INDEPENDENT WORKS #
A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.
8. TRANSLATION #
Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.
If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.
9. TERMINATION #
You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
10. FUTURE REVISIONS OF THIS LICENSE #
The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See https://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.
ADDENDUM: How to use this License for your documents #
Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:
with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.