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Applies to SUSE Linux Enterprise Server 11 SP4

36 Common Problems and Their Solutions

This chapter describes a range of potential problems and their solutions. Even if your situation is not precisely listed here, there may be one similar enough to offer hints to the solution of your problem.

36.1 Finding and Gathering Information

Linux reports things in a very detailed way. There are several places to look when you encounter problems with your system, most of which are standard to Linux systems in general, and some of which are relevant to SUSE Linux Enterprise Server systems. Most log files can be viewed with YaST (Miscellaneous › Start-Up Log).

YaST offers the possibility to collect all system information needed by the support team. Use Other › Support and select the problem category. When all information is gathered, attach it to your support request.

A list of the most frequently checked log files follows with the description of their typical purpose. Paths containing ~ refer to the current user's home directory.

Table 36.1: Log Files

Log File

Description

~/.xsession-errors

Messages from the desktop applications currently running.

/var/log/apparmor/

Log files from AppArmor, see Part IV, “Confining Privileges with AppArmor” for detailed information.

/var/log/audit/audit.log

Log file from Audit to track any access to files, directories, or resources of your system, and trace system calls.

/var/log/boot.msg

Messages from the kernel reported during the boot process.

/var/log/mail.*

Messages from the mail system.

/var/log/messages

Ongoing messages from the kernel and system log daemon (when running).

/var/log/NetworkManager

Log file from NetworkManager to collect problems with network connectivity

/var/log/samba/

Directory containing Samba server and client log messages.

/var/log/SaX.log

Hardware messages from the SaX display and KVM system.

/var/log/warn

All messages from the kernel and system log daemon with the warning level or higher.

/var/log/wtmp

Binary file containing user login records for the current machine session. View it with last.

/var/log/Xorg.*.log

Various start-up and runtime logs from the X Window system. It is useful for debugging failed X start-ups.

/var/log/YaST2/

Directory containing YaST's actions and their results.

/var/log/zypper.log

Log file of zypper.

Apart from log files, your machine also supplies you with information about the running system. See Table 36.2: System Information With the /proc File System

Table 36.2: System Information With the /proc File System

File

Description

/proc/cpuinfo

Contains processor information, including its type, make, model, and performance.

/proc/dma

Shows which DMA channels are currently being used.

/proc/interrupts

Shows which interrupts are in use, and how many of each have been in use.

/proc/iomem

Displays the status of I/O (input/output) memory.

/proc/ioports

Shows which I/O ports are in use at the moment.

/proc/meminfo

Displays memory status.

/proc/modules

Displays the individual modules.

/proc/mounts

Displays devices currently mounted.

/proc/partitions

Shows the partitioning of all hard disks.

/proc/version

Displays the current version of Linux.

Apart from the /proc file system, the Linux kernel exports information with the sysfs module, an in-memory file system. This module represents kernel objects, their attributes and relationships. For more information about sysfs, see the context of udev in Chapter 15, Dynamic Kernel Device Management with udev. Table 36.3 contains an overview of the most common directories under /sys.

Table 36.3: System Information With the /sys File System

File

Description

/sys/block

Contains subdirectories for each block device discovered in the system. Generally, these are mostly disk type devices.

/sys/bus

Contains subdirectories for each physical bus type.

/sys/class

Contains subdirectories grouped together as a functional types of devices (like graphics, net, printer, etc.)

/sys/device

Contains the global device hierarchy.

Linux comes with a number of tools for system analysis and monitoring. See Chapter 2, System Monitoring Utilities for a selection of the most important ones used in system diagnostics.

Each of the following scenarios begins with a header describing the problem followed by a paragraph or two offering suggested solutions, available references for more detailed solutions, and cross-references to other scenarios that are related.

36.2 Installation Problems

Installation problems are situations when a machine fails to install. It may fail entirely or it may not be able to start the graphical installer. This section highlights some of the typical problems you may run into, and offers possible solutions or workarounds for these kinds of situations.

36.2.1 Checking Media

If you encounter any problems using the SUSE Linux Enterprise Server installation media, check the integrity of your installation media with Software › Media Check. Media problems are more probable with the media you burn yourself. To check the SUSE Linux Enterprise Server medium, insert it into the drive and click Start Check in the Media Check screen of YaST. This may take several minutes. If errors are detected, do not use this medium for installation.

Checking Media
Figure 36.1: Checking Media

36.2.2 Hardware Information

Display detected hardware and technical data using Hardware › Hardware Information. Click any node of the tree for more information about a device. This module is especially useful, when submitting a support request for which you need information about your hardware.

Save the displayed hardware information to a file by clicking Save to File. Select the desired directory and filename then click Save to create the file.

Displaying Hardware Information
Figure 36.2: Displaying Hardware Information

36.2.3 No Bootable DVD Drive Available

If your computer does not contain a bootable DVD-ROM drive or if the one you have is not supported by Linux, there are several options you can install your machine without a built-in DVD drive:

Booting from a Floppy Disk

Create a boot floppy and boot from floppy disk instead of DVD.

Using an External Boot Device

If it is supported by your BIOS and the installation kernel, boot from external DVD drives.

Network Boot via PXE

If a machine lacks a DVD drive, but provides a working ethernet connection, perform a completely network-based installation. See Section 14.1.3, “Remote Installation via VNC—PXE Boot and Wake on LAN” and Section 14.1.6, “Remote Installation via SSH—PXE Boot and Wake on LAN” for details.

36.2.3.1 Booting from a Floppy Disk (SYSLINUX)

On some older computers, there is no bootable DVD drive available, but there is a floppy disk drive present. To install on such a system, create boot disks and boot your system with them.

The boot disks include the loader called SYSLINUX and the program linuxrc. SYSLINUX enables the selection of a kernel during the boot procedure and the specification of any parameters needed for the hardware used. The program linuxrc supports the loading of kernel modules for your hardware and subsequently starts the installation.

When booting from a boot disk, the boot procedure is initiated by the boot loader SYSLINUX (package syslinux). When the system is booted, SYSLINUX runs a minimum hardware detection that mainly consists of the following steps:

  1. The program checks if the BIOS provides VESA 2.0–compliant framebuffer support and boots the kernel accordingly.

  2. The monitor data (DDC info) is read.

  3. The first block of the first hard disk (MBR) is read to map BIOS IDs to Linux device names during the boot loader configuration. The program attempts to read the block by means of the the lba32 functions of the BIOS to determine if the BIOS supports these functions.

If you keep Shift pressed when SYSLINUX starts, all these steps are skipped. For troubleshooting purposes, insert the line

verbose 1

in syslinux.cfg for the boot loader to display which action is currently being performed.

If the machine does not boot from the floppy disk, you may need to change the boot sequence in the BIOS to A,C,CDROM.

36.2.3.2 External Boot Devices

Linux supports most existing DVD drives. If the system has neither a DVD drive nor a floppy disk, it is still possible that an external DVD drive, connected through USB, FireWire, or SCSI, can be used to boot the system. This depends mainly on the interaction of the BIOS and the hardware used. Sometimes a BIOS update may help if you encounter problems.

36.2.4 Booting from Installation Media Fails

One reason why a machine does not boot the installation media can be an incorrect boot sequence setting in BIOS. The BIOS boot sequence must have DVD drive set as the first entry for booting. Otherwise the machine would try to boot from another medium, typically the hard disk. Guidance for changing the BIOS boot sequence can be found the documentation provided with your motherboard, or in the following paragraphs.

The BIOS is the software that enables the very basic functions of a computer. Motherboard vendors provide a BIOS specifically made for their hardware. Normally, the BIOS setup can only be accessed at a specific time—when the machine is booting. During this initialization phase, the machine performs a number of diagnostic hardware tests. One of them is a memory check, indicated by a memory counter. When the counter appears, look for a line, usually below the counter or somewhere at the bottom, mentioning the key to press to access the BIOS setup. Usually the key to press is one of Del, F1, or Esc. Press this key until the BIOS setup screen appears.

Procedure 36.1: Changing the BIOS Boot Sequence
  1. Enter the BIOS using the proper key as announced by the boot routines and wait for the BIOS screen to appear.

  2. To change the boot sequence in an AWARD BIOS, look for the BIOS FEATURES SETUP entry. Other manufacturers may have a different name for this, such as ADVANCED CMOS SETUP. When you have found the entry, select it and confirm with Enter.

  3. In the screen that opens, look for a subentry called BOOT SEQUENCE or BOOT ORDER. The boot sequence looks something like C,A or A,C. In the former case, the machine first searches the hard disk (C) then the floppy drive (A) to find a bootable medium. Change the settings by pressing PgUp or PgDown until the sequence is A,CDROM,C.

  4. Leave the BIOS setup screen by pressing Esc. To save the changes, select SAVE & EXIT SETUP, or press F10. To confirm that your settings should be saved, press Y.

Procedure 36.2: Changing the Boot Sequence in a SCSI BIOS (Adaptec Host Adapter)
  1. Open the setup by pressing CtrlA.

  2. Select Disk Utilities. The connected hardware components are now displayed.

    Make note of the SCSI ID of your DVD drive.

  3. Exit the menu with Esc.

  4. Open Configure Adapter Settings. Under Additional Options, select Boot Device Options and press Enter.

  5. Enter the ID of the DVD drive and press Enter again.

  6. Press Esc twice to return to the start screen of the SCSI BIOS.

  7. Exit this screen and confirm with Yes to boot the computer.

Regardless of what language and keyboard layout your final installation will be using, most BIOS configurations use the US keyboard layout as depicted in the following figure:

US Keyboard Layout
Figure 36.3: US Keyboard Layout

36.2.5 Fails to Boot

Some hardware types, mainly very old or very recent ones, fail to install. In many cases, this may happen because support for this type of hardware is missing in the installation kernel, or due to certain functionality included in this kernel, such as ACPI, that can still cause problems on some hardware.

If your system fails to install using the standard Installation mode from the first installation boot screen, try the following:

  1. With the DVD still in the drive, reboot the machine with CtrlAltDel or using the hardware reset button.

  2. When the boot screen appears, press F5, use the arrow keys of your keyboard to navigate to No ACPI and press Enter to launch the boot and installation process. This option disables the support for ACPI power management techniques.

  3. Proceed with the installation as described in Chapter 6, Installation with YaST.

If this fails, proceed as above, but choose Safe Settings instead. This option disables ACPI and DMA support. Most hardware will boot with this option.

If both of these options fail, use the boot options prompt to pass any additional parameters needed to support this type of hardware to the installation kernel. For more information about the parameters available as boot options, refer to the kernel documentation located in /usr/src/linux/Documentation/kernel-parameters.txt.

Tip
Tip: Obtaining Kernel Documentation

Install the kernel-source package to view the kernel documentation.

There are various other ACPI-related kernel parameters that can be entered at the boot prompt prior to booting for installation:

acpi=off

This parameter disables the complete ACPI subsystem on your computer. This may be useful if your computer cannot handle ACPI at all or if you think ACPI in your computer causes trouble.

acpi=force

Always enable ACPI even if your computer has an old BIOS dated before the year 2000. This parameter also enables ACPI if it is set in addition to acpi=off.

acpi=noirq

Do not use ACPI for IRQ routing.

acpi=ht

Run only enough ACPI to enable hyper-threading.

acpi=strict

Be less tolerant of platforms that are not strictly ACPI specification compliant.

pci=noacpi

Disable PCI IRQ routing of the new ACPI system.

pnpacpi=off

This option is for serial or parallel problems when your BIOS setup contains wrong interrupts or ports.

notsc

Disable the time stamp counter. This option can be used to work around timing problems on your systems. It is a recent feature, if you see regressions on your machine, especially time related or even total hangs, this option is worth a try.

nohz=off

Disable the nohz feature. If your machine hangs, this option may help. Otherwise it is of no use.

Once you have determined the right parameter combination, YaST automatically writes them to the boot loader configuration to make sure that the system boots properly next time.

If unexplainable errors occur when the kernel is loaded or during the installation, select Memory Test in the boot menu to check the memory. If Memory Test returns an error, it is usually a hardware error.

36.2.6 Fails to Launch Graphical Installer

After you insert the medium into your drive and reboot your machine, the installation screen comes up, but after you select Installation, the graphical installer does not start.

There are several ways to deal with this situation:

  • Try to select another screen resolution for the installation dialogs.

  • Select Text Mode for installation.

  • Do a remote installation via VNC using the graphical installer.

Procedure 36.3: Change Screen Resolution for Installation
  1. Boot for installation.

  2. Press F3 to open a menu from which to select a lower resolution for installation purposes.

  3. Select Installation and proceed with the installation as described in Chapter 6, Installation with YaST.

Procedure 36.4: Installation in Text Mode
  1. Boot for installation.

  2. Press F3 and select Text Mode.

  3. Select Installation and proceed with the installation as described in Chapter 6, Installation with YaST.

Procedure 36.5: VNC Installation
  1. Boot for installation.

  2. Enter the following text at the boot options prompt:

    vnc=1 vncpassword=some_password

    Replace some_password with the password to use for VNC installation.

  3. Select Installation then press Enter to start the installation.

    Instead of starting right into the graphical installation routine, the system continues to run in a text mode, then halts, displaying a message containing the IP address and port number at which the installer can be reached via a browser interface or a VNC viewer application.

  4. If using a browser to access the installer, launch the browser and enter the address information provided by the installation routines on the future SUSE Linux Enterprise Server machine and hit Enter:

    http://ip_address_of_machine:5801

    A dialog opens in the browser window prompting you for the VNC password. Enter it and proceed with the installation as described in Chapter 6, Installation with YaST.

    Important
    Important

    Installation via VNC works with any browser under any operating system, provided Java support is enabled.

    Provide the IP address and password to your VNC viewer when prompted. A window opens, displaying the installation dialogs. Proceed with the installation as usual.

36.2.7 Only Minimalistic Boot Screen Started

You inserted the medium into the drive, the BIOS routines are finished, but the system does not start with the graphical boot screen. Instead it launches a very minimalistic text-based interface. This may happen on any machine not providing sufficient graphics memory for rendering a graphical boot screen.

Although the text boot screen looks minimalistic, it provides nearly the same functionality as the graphical one:

Boot Options

Unlike the graphical interface, the different boot options cannot be selected using the cursor keys of your keyboard. The boot menu of the text mode boot screen offers some keywords to enter at the boot prompt. These keywords map to the options offered in the graphical version. Enter your choice and hit Enter to launch the boot process.

Custom Boot Options

After selecting a boot option, enter the appropriate keyword at the boot prompt or enter some custom boot options as described in Section 36.2.5, “Fails to Boot”. To launch the installation process, press Enter.

Screen Resolutions

Use the F keys to determine the screen resolution for installation. If you need to boot in text mode, choose F3.

36.3 Boot Problems

Boot problems are situations when your system does not boot properly (does not boot to the expected runlevel and login screen).

36.3.1 Fails to Load the GRUB Boot Loader

If the hardware is functioning properly, it is possible that the boot loader is corrupted and Linux cannot start on the machine. In this case, it is necessary to reinstall the boot loader. To reinstall the boot loader, proceed as follows:

  1. Insert the installation media into the drive.

  2. Reboot the machine.

  3. Select Installation from the boot menu.

  4. Select a language.

  5. Accept the license agreement.

  6. In the Installation Mode screen, select Repair Installed System.

  7. Once in the YaST System Repair module, select Expert Tools then select Install New Boot Loader.

  8. Restore the original settings and reinstall the boot loader.

  9. Leave YaST System Repair and reboot the system.

Other reasons for the machine not booting may be BIOS-related:

BIOS Settings

Check your BIOS for references to your hard drive. GRUB may simply not be started if the hard drive itself cannot be found with the current BIOS settings.

BIOS Boot Order

Check whether your system's boot order includes the hard disk. If the hard disk option was not enabled, your system may install properly, but fails to boot when access to the hard disk is required.

36.3.2 No Graphical Login

If the machine comes up, but does not boot into the graphical login manager, anticipate problems either with the choice of the default runlevel or the configuration of the X Window System. To check the runlevel configuration, log in as the root user and check whether the machine is configured to boot into runlevel 5 (graphical desktop). A quick way to check this is to examine the contents of /etc/inittab, as follows:

tux@mercury:~> grep "id:" /etc/inittab 
id:5:initdefault:

The returned line indicates that the machine's default runlevel (initdefault) is set to 5 and that it should boot to the graphical desktop. If the runlevel is set to any other number, use the YaST Runlevel Editor module to set it to 5.

Important
Important

Do not edit the runlevel configuration manually. Otherwise SuSEconfig (run by YaST) will overwrite these changes on its next run. If you need to make manual changes here, disable future SuSEconfig changes by setting CHECK_INITTAB in /etc/sysconfig/suseconfig to no.

If the runlevel is set to 5, your desktop or X Windows software is probably misconfigured or corrupted. Examine the log files at /var/log/Xorg.*.log for detailed messages from the X server as it attempted to start. If the desktop fails during start, it may log error messages to /var/log/messages. If these error messages hint at a configuration problem in the X server, try to fix these issues. If the graphical system still does not come up, consider reinstalling the graphical desktop.

Tip
Tip: Starting X Window System Manually

One quick test: the startx command should force the X Window System to start with the configured defaults if the user is currently logged in on the console. If that does not work, it should log errors to the console.

36.4 Login Problems

Login problems are those where your machine does, in fact, boot to the expected welcome screen or login prompt, but refuses to accept the username and password, or accepts them but then does not behave properly (fails to start the graphic desktop, produces errors, drops to a command line, etc.).

36.4.1 Valid Username and Password Combinations Fail

This usually occurs when the system is configured to use network authentication or directory services and, for some reason, is unable to retrieve results from its configured servers. The root user, as the only local user, is the only user that can still log in to these machines. The following are some common reasons why a machine appears functional but is unable to process logins correctly:

  • The network is not working. For further directions on this, turn to Section 36.5, “Network Problems”.

  • DNS is not working at the moment (which prevents GNOME or KDE from working and the system from making validated requests to secure servers). One indication that this is the case is that the machine takes an extremely long time to respond to any action. Find more information about this topic in Section 36.5, “Network Problems”.

  • If the system is configured to use Kerberos, the system's local time may have drifted past the accepted variance with the Kerberos server time (this is typically 300 seconds). If NTP (network time protocol) is not working properly or local NTP servers are not working, Kerberos authentication ceases to function because it depends on common clock synchronization across the network.

  • The system's authentication configuration is misconfigured. Check the PAM configuration files involved for any typographical errors or misordering of directives. For additional background information about PAM and the syntax of the configuration files involved, refer to Chapter 2, Authentication with PAM.

  • The home partition is encrypted. Find more information about this topic in Section 36.4.3, “Login to Encrypted Home Partition Fails”.

In all cases that do not involve external network problems, the solution is to reboot the system into single-user mode and repair the configuration before booting again into operating mode and attempting to log in again. To boot into single-user mode:

  1. Reboot the system. The boot screen appears, offering a prompt.

  2. Enter 1 at the boot prompt to make the system boot into single-user mode.

  3. Enter the username and password for root.

  4. Make all the necessary changes.

  5. Boot into the full multiuser and network mode by entering telinit 5 at the command line.

36.4.2 Valid Username and Password Not Accepted

This is by far the most common problem users encounter, because there are many reasons this can occur. Depending on whether you use local user management and authentication or network authentication, login failures occur for different reasons.

Local user management can fail for the following reasons:

  • The user may have entered the wrong password.

  • The user's home directory containing the desktop configuration files is corrupted or write protected.

  • There may be problems with the X Window System authenticating this particular user, especially if the user's home directory has been used with another Linux distribution prior to installing the current one.

To locate the reason for a local login failure, proceed as follows:

  1. Check whether the user remembered his password correctly before you start debugging the whole authentication mechanism. If the user may not remember his password correctly, use the YaST User Management module to change the user's password. Pay attention to the Caps Lock key and unlock it, if necessary.

  2. Log in as root and check /var/log/messages for error messages of the login process and of PAM.

  3. Try to log in from a console (using CtrlAltF1). If this is successful, the blame cannot be put on PAM, because it is possible to authenticate this user on this machine. Try to locate any problems with the X Window System or the desktop (GNOME or KDE). For more information, refer to Section 36.4.4, “Login Successful but GNOME Desktop Fails” and Section 36.4.5, “Login Successful but KDE Desktop Fails”.

  4. If the user's home directory has been used with another Linux distribution, remove the Xauthority file in the user's home. Use a console login via CtrlAltF1 and run rm .Xauthority as this user. This should eliminate X authentication problems for this user. Try graphical login again.

  5. If graphical login still fails, do a console login with CtrlAltF1. Try to start an X session on another display—the first one (:0) is already in use:

    startx -- :1

    This should bring up a graphical screen and your desktop. If it does not, check the log files of the X Window System (/var/log/Xorg.displaynumber.log) or the log file for your desktop applications (.xsession-errors in the user's home directory) for any irregularities.

  6. If the desktop could not start because of corrupt configuration files, proceed with Section 36.4.4, “Login Successful but GNOME Desktop Fails” or Section 36.4.5, “Login Successful but KDE Desktop Fails”.

The following are some common reasons why network authentication for a particular user may fail on a specific machine:

  • The user may have entered the wrong password.

  • The username exists in the machine's local authentication files and is also provided by a network authentication system, causing conflicts.

  • The home directory exists but is corrupt or unavailable. Perhaps it is write protected or is on a server that is inaccessible at the moment.

  • The user does not have permission to log in to that particular host in the authentication system.

  • The machine has changed hostnames, for whatever reason, and the user does not have permission to log in to that host.

  • The machine cannot reach the authentication server or directory server that contains that user's information.

  • There may be problems with the X Window System authenticating this particular user, especially if the user's home has been used with another Linux distribution prior to installing the current one.

To locate the cause of the login failures with network authentication, proceed as follows:

  1. Check whether the user remembered their password correctly before you start debugging the whole authentication mechanism.

  2. Determine the directory server which the machine relies on for authentication and make sure that it is up and running and properly communicating with the other machines.

  3. Determine that the user's username and password work on other machines to make sure that his authentication data exists and is properly distributed.

  4. See if another user can log in to the misbehaving machine. If another user can log in without difficulty or if root can log in, log in and examine the /var/log/messages file. Locate the time stamps that correspond to the login attempts and determine if PAM has produced any error messages.

  5. Try to log in from a console (using CtrlAltF1). If this is successful, the problem is not with PAM or the directory server on which the user's home is hosted, because it is possible to authenticate this user on this machine. Try to locate any problems with the X Window System or the desktop (GNOME or KDE). For more information, refer to Section 36.4.4, “Login Successful but GNOME Desktop Fails” and Section 36.4.5, “Login Successful but KDE Desktop Fails”.

  6. If the user's home directory has been used with another Linux distribution, remove the Xauthority file in the user's home. Use a console login via CtrlAltF1 and run rm .Xauthority as this user. This should eliminate X authentication problems for this user. Try graphical login again.

  7. If graphical login still fails, do a console login with CtrlAltF1. Try to start an X session on another display—the first one (:0) is already in use:

    startx -- :1

    This should bring up a graphical screen and your desktop. If it does not, check the log files of the X Window System (/var/log/Xorg.displaynumber.log) or the log file for your desktop applications (.xsession-errors in the user's home directory) for any irregularities.

  8. If the desktop could not start because of corrupt configuration files, proceed with Section 36.4.4, “Login Successful but GNOME Desktop Fails” or Section 36.4.5, “Login Successful but KDE Desktop Fails”.

36.4.3 Login to Encrypted Home Partition Fails

It is recommended to use an encrypted home partition for laptops. If you cannot log in to your laptop, the reason is usually simple: your partition could not be unlocked.

During the boot time, you have to enter the passphrase to unlock your encrypted partition. If you do not enter it, the boot process continues, leaving the partition locked.

To unlock your encrypted partition, proceed as follows:

  1. Switch to the text console with CtrlAltF1.

  2. Become root.

  3. Restart the unlocking process again with:

    /etc/init.d/boot.crypto restart
  4. Enter your passphrase to unlock your encrypted partition.

  5. Exit the text console and switch back to the login screen with AltF7.

  6. Log in as usual.

36.4.4 Login Successful but GNOME Desktop Fails

If this is the case, it is likely that your GNOME configuration files have become corrupted. Some symptoms may include the keyboard failing to work, the screen geometry becoming distorted, or even the screen coming up as a bare gray field. The important distinction is that if another user logs in, the machine works normally. It is then likely that the problem can be fixed relatively quickly by simply moving the user's GNOME configuration directory to a new location, which causes GNOME to initialize a new one. Although the user is forced to reconfigure GNOME, no data is lost.

  1. Switch to a text console by pressing CtrlAltF1.

  2. Log in with your username.

  3. Move the user's GNOME configuration directories to a temporary location:

    mv .gconf  .gconf-ORIG-RECOVER
    mv .gnome2 .gnome2-ORIG-RECOVER
  4. Log out.

  5. Log in again, but do not run any applications.

  6. Recover your individual application configuration data (including the Evolution e-mail client data) by copying the ~/.gconf-ORIG-RECOVER/apps/ directory back into the new ~/.gconf directory as follows:

    cp -a .gconf-ORIG-RECOVER/apps .gconf/

    If this causes the login problems, attempt to recover only the critical application data and reconfigure the remainder of the applications.

36.4.5 Login Successful but KDE Desktop Fails

There are several reasons why a KDE desktop would not allow users to login. Corrupted cache data can cause login problems as well as corrupt KDE desktop configuration files.

Cache data is used at desktop start-up to increase performance. If this data is corrupted, start-up is slowed down or fails entirely. Removing them forces the desktop start-up routines to start from scratch. This takes more time than a normal start-up, but data is intact after this and the user can login.

To remove the cache files of the KDE desktop, issue the following command as root:

rm -rf /tmp/kde-user /tmp/ksocket-user

Replace user with your username. Removing these two directories just removes the corrupted cache files. No real data is harmed using this procedure.

Corrupted desktop configuration files can always be replaced with the initial configuration files. If you want to recover the user's adjustments, carefully copy them back from their temporary location after the configuration has been restored, using the default configuration values.

To replace a corrupted desktop configuration with the initial configuration values, proceed as follows:

  1. Switch to a text console by pressing CtrlAltF1.

  2. Log in with your username.

  3. Move the KDE configuration directory and the .skel files to a temporary location:

    • For KDE3 use these commands:

      mv .kde  .kde-ORIG-RECOVER 
      mv .skel .skel-ORIG-RECOVER
    • For KDE4 use these commands:

      mv .kde4  .kde4-ORIG-RECOVER 
      mv .skel .skel-ORIG-RECOVER
  4. Log out.

  5. Log in again.

  6. After the desktop has started successfully, copy the user's own configurations back into place:

    cp -a KDEDIR/share .kde/share

    Replace KDEDIR with the directory from Step 3.

    Important
    Important

    If the user's own adjustments caused the login to fail and continue to do so, repeat the procedure as described above, but do not copy the .kde/share directory.

36.5 Network Problems

Many problems of your system may be network-related, even though they do not seem to be at first. For example, the reason for a system not allowing users to log in may be a network problem of some kind. This section introduces a simple checklist you can apply to identify the cause of any network problem encountered.

Procedure 36.6: How to Identify Network Problems

When checking the network connection of your machine, proceed as follows:

  1. If you use an ethernet connection, check the hardware first. Make sure that your network cable is properly plugged into your computer and router (or hub, etc.). The control lights next to your ethernet connector are normally both be active.

    If the connection fails, check whether your network cable works with another machine. If it does, your network card causes the failure. If hubs or switches are included in your network setup, they may be faulty, as well.

  2. If using a wireless connection, check whether the wireless link can be established by other machines. If not, contact the wireless network's administrator.

  3. Once you have checked your basic network connectivity, try to find out which service is not responding. Gather the address information of all network servers needed in your setup. Either look them up in the appropriate YaST module or ask your system administrator. The following list gives some of the typical network servers involved in a setup together with the symptoms of an outage.

    DNS (Name Service)

    A broken or malfunctioning name service affects the network's functionality in many ways. If the local machine relies on any network servers for authentication and these servers cannot be found due to name resolution issues, users would not even be able to log in. Machines in the network managed by a broken name server would not be able to see each other and communicate.

    NTP (Time Service)

    A malfunctioning or completely broken NTP service could affect Kerberos authentication and X server functionality.

    NFS (File Service)

    If any application needs data stored in an NFS mounted directory, it will not be able to start or function properly if this service was down or misconfigured. In the worst case scenario, a user's personal desktop configuration would not come up if their home directory containing the .gconf or .kde subdirectories could not be found due to a faulty NFS server.

    Samba (File Service)

    If any application needs data stored in a directory on a faulty Samba server, it will not be able to start or function properly.

    NIS (User Management)

    If your SUSE Linux Enterprise Server system relies on a faulty NIS server to provide the user data, users will not be able to log in to this machine.

    LDAP (User Management)

    If your SUSE Linux Enterprise Server system relies on a faulty LDAP server to provide the user data, users will not be able to log in to this machine.

    Kerberos (Authentication)

    Authentication will not work and login to any machine fails.

    CUPS (Network Printing)

    Users cannot print.

  4. Check whether the network servers are running and whether your network setup allows you to establish a connection:

    Important
    Important

    The debugging procedure described below only applies to a simple network server/client setup that does not involve any internal routing. It assumes both server and client are members of the same subnet without the need for additional routing.

    1. Use ping IP address or hostname (replace hostname with the hostname of the server) to check whether each one of them is up and responding to the network. If this command is successful, it tells you that the host you were looking for is up and running and that the name service for your network is configured correctly.

      If ping fails with destination host unreachable, either your system or the desired server is not properly configured or down. Check whether your system is reachable by running ping IP address or your_hostname from another machine. If you can reach your machine from another machine, it is the server that is not running at all or not configured correctly.

      If ping fails with unknown host, the name service is not configured correctly or the hostname used was incorrect. For further checks on this matter, refer to Step 4.b. If ping still fails, either your network card is not configured correctly or your network hardware is faulty.

    2. Use host hostname to check whether the hostname of the server you are trying to connect to is properly translated into an IP address and vice versa. If this command returns the IP address of this host, the name service is up and running. If the host command fails, check all network configuration files relating to name and address resolution on your host:

      /etc/resolv.conf

      This file is used to keep track of the name server and domain you are currently using. It can be modified manually or automatically adjusted by YaST or DHCP. Automatic adjustment is preferable. However, make sure that this file has the following structure and all network addresses and domain names are correct:

      search fully_qualified_domain_name
      nameserver ipaddress_of_nameserver

      This file can contain more than one name server address, but at least one of them must be correct to provide name resolution to your host. If needed, adjust this file using the YaST Network Setting module (Hostname/DNS tab).

      If your network connection is handled via DHCP, enable DHCP to change hostname and name service information by selecting Change Hostname via DHCP and Update Name Servers and Search List via DHCP in the YaST DNS and Hostname module.

      /etc/nsswitch.conf

      This file tells Linux where to look for name service information. It should look like this:

       ...
      hosts: files dns
      networks: files dns
      ...

      The dns entry is vital. It tells Linux to use an external name server. Normally, these entries are automatically managed by YaST, but it would be prudent to check.

      If all the relevant entries on the host are correct, let your system administrator check the DNS server configuration for the correct zone information. For detailed information about DNS, refer to Chapter 25, The Domain Name System. If you have made sure that the DNS configuration of your host and the DNS server are correct, proceed with checking the configuration of your network and network device.

    3. If your system cannot establish a connection to a network server and you have excluded name service problems from the list of possible culprits, check the configuration of your network card.

      Use the command ifconfig network_device (executed as root) to check whether this device was properly configured. Make sure that both inet address and Mask are configured correctly. An error in the IP address or a missing bit in your network mask would render your network configuration unusable. If necessary, perform this check on the server as well.

    4. If the name service and network hardware are properly configured and running, but some external network connections still get long time-outs or fail entirely, use traceroute fully_qualified_domain_name (executed as root) to track the network route these requests are taking. This command lists any gateway (hop) that a request from your machine passes on its way to its destination. It lists the response time of each hop and whether this hop is reachable at all. Use a combination of traceroute and ping to track down the culprit and let the administrators know.

Once you have identified the cause of your network trouble, you can resolve it yourself (if the problem is located on your machine) or let the system administrators of your network know about your findings so they can reconfigure the services or repair the necessary systems.

36.5.1 NetworkManager Problems

If you have a problem with network connectivity, narrow it down as described in Procedure 36.6, “How to Identify Network Problems”. If NetworkManager seems to be the culprit, proceed as follows to get logs providing hints on why NetworkManager fails:

  1. Open a shell and log in as root.

  2. Restart the NetworkManager:

    rcnetwork restart -o nm
  3. Open a Web page, for example, http://www.opensuse.org as normal user to see, if you can connect.

  4. Collect any information about the state of NetworkManager in /var/log/NetworkManager.

For more information about NetworkManager, refer to Chapter 27, Using NetworkManager.

36.6 Data Problems

Data problems are when the machine may or may not boot properly but, in either case, it is clear that there is data corruption on the system and that the system needs to be recovered. These situations call for a backup of your critical data, enabling you to recover the system state from before your system failed. SUSE Linux Enterprise Server offers dedicated YaST modules for system backup and restoration as well as a rescue system that can be used to recover a corrupted system from the outside.

36.6.1 Managing Partition Images

Sometimes you need to perform a backup from an entire partition or even hard disk. Linux comes with the dd tool which can create a exact copy of your disc. Combined with gzip you save some space.

Procedure 36.7: Backing up and Restoring Harddisks
  1. Start a Shell as user root.

  2. Select your source device. Typically this is something like /dev/sda (labeled as SOURCE).

  3. Decide where you want to store your image (labeled as BACKUP_PATH). It must be different from your source device. In other words: if you make a backup from /dev/sda, your image file must not to be stored under /dev/sda.

  4. Run the commands to create a compressed image file:

    dd if=/dev/SOURCE | gzip > /BACKUP_PATH/image.gz
  5. Restore the hard disk with the following commands:

    gzip -dc /BACKUP_PATH/image.gz | dd of=/dev/SOURCE

If you only need a partition to backup, replace the SOURCE placeholder with your respective partition. In this case, your image file can lie on the same hard disk, but on a different partition.

36.6.2 Backing Up Critical Data

System backups can be easily managed using the YaST System Backup module:

  1. As root, start YaST and select System › System Backup.

  2. Create a backup profile holding all details needed for the backup, filename of the archive file, scope, and type of the backup:

    1. Select Profile Management › Add.

    2. Enter a name for the archive.

    3. Enter the path to the location of the backup if you want to keep a local backup. For your backup to be archived on a network server (via NFS), enter the IP address or name of the server and the directory that should hold your archive.

    4. Determine the archive type and click Next.

    5. Determine the backup options to use, such as whether files not belonging to any package should be backed up and whether a list of files should be displayed prior to creating the archive. Also determine whether changed files should be identified using the time-consuming MD5 mechanism.

      Use Expert to enter a dialog for the backup of entire hard disk areas. Currently, this option only applies to the Ext2 file system.

    6. Finally, set the search constraints to exclude certain system areas from the backup area that do not need to be backed up, such as lock files or cache files. Add, edit, or delete items until your needs are met and leave with OK.

  3. Once you have finished the profile settings, you can start the backup right away with Create Backup or configure automatic backup. It is also possible to create other profiles tailored for various other purposes.

To configure automatic backup for a given profile, proceed as follows:

  1. Select Automatic Backup from the Profile Management menu.

  2. Select Start Backup Automatically.

  3. Determine the backup frequency. Choose daily, weekly, or monthly.

  4. Determine the backup start time. These settings depend on the backup frequency selected.

  5. Decide whether to keep old backups and how many should be kept. To receive an automatically generated status message of the backup process, check Send Summary Mail to User root.

  6. Click OK to apply your settings and have the first backup start at the time specified.

36.6.3 Restoring a System Backup

Use the YaST System Restoration module to restore the system configuration from a backup. Restore the entire backup or select specific components that were corrupted and need to be reset to their old state.

  1. Start YaST › System › System Restoration.

  2. Enter the location of the backup file. This could be a local file, a network mounted file, or a file on a removable device, such as a floppy or a DVD. Then click Next.

    The following dialog displays a summary of the archive properties, such as the filename, date of creation, type of backup, and optional comments.

  3. Review the archived content by clicking Archive Content. Clicking OK returns you to the Archive Properties dialog.

  4. Expert Options opens a dialog in which to fine-tune the restore process. Return to the Archive Properties dialog by clicking OK.

  5. Click Next to open the view of packages to restore. Press Accept to restore all files in the archive or use the various Select All, Deselect All, and Select Files buttons to fine-tune your selection. Only use the Restore RPM Database option if the RPM database is corrupted or deleted and this file is included in the backup.

  6. After you click Accept, the backup is restored. Click Finish to leave the module after the restore process is completed.

36.6.4 Recovering a Corrupted System

There are several reasons why a system could fail to come up and run properly. A corrupted file system following a system crash, corrupted configuration files, or a corrupted boot loader configuration are the most common ones.

SUSE Linux Enterprise Server offers two different methods to resolve these situations. You can either use the YaST System Repair functionality or boot the rescue system. The following sections cover both types of system repair methods.

36.6.4.1 Using YaST System Repair

Note
Note: Keyboard and Language Settings

If you change the language settings after booting, your keyboard is adapted as well.

Before launching the YaST System Repair module, determine in which mode to run it to best fit your needs. Depending on the severity and cause of your system failure (and your expertise), there are three different modes to choose from:

Automatic Repair

If your system failed due to an unknown cause and you basically do not know which part of the system is to blame for the failure, use Automatic Repair. An extensive automated check will be performed on all components of your installed system. For a detailed description of this procedure, refer to Section 36.6.4.1.1, “Automatic Repair”.

Customized Repair

If your system failed and you already know which component is to blame, you can cut the lengthy system check with Automatic Repair short by limiting the scope of the system analysis to those components. For example, if the system messages prior to the failure seem to indicate an error with the package database, you can limit the analysis and repair procedure to checking and restoring this aspect of your system. For a detailed description of this procedure, refer to Section 36.6.4.1.2, “Customized Repair”.

Expert Tools

If you already have a clear idea of what component failed and how this should be fixed, you can skip the analysis runs and directly apply the tools necessary for the repair of the relevant component. For details, refer to Section 36.6.4.1.3, “Expert Tools”.

Choose one of the repair modes as described above and proceed with the system repair as outlined in the following sections.

36.6.4.1.1 Automatic Repair

To start the automatic repair mode of YaST System Repair, proceed as follows:

  1. Insert the installation medium of SUSE Linux Enterprise Server into your DVD drive.

  2. Reboot the system.

  3. On the boot screen, select Repair Installed System.

  4. Confirm the license agreement and click Next.

  5. Select Automatic Repair.

    YaST now launches an extensive analysis of the installed system. The progress of the procedure is displayed at the bottom of the screen with two progress bars. The upper bar shows the progress of the currently running test. The lower bar shows the overall progress of the analysis. The log window in the top section tracks the currently running test and its result. See Figure 36.4, “Automatic Repair Mode”.

    Automatic Repair Mode
    Figure 36.4: Automatic Repair Mode

    The following main test runs are performed with every run. They contain, in turn, a number of individual subtests:

    Check Partition Tables

    Checks the validity and coherence of the partition tables of all detected hard disks.

    Check Swap Areas

    The swap partitions of the installed system are detected, tested, and offered for activation, where applicable. This offer should be accepted for the sake of a higher system repair speed.

    Check File Systems

    All detected file systems are subjected to a file system–specific check.

    Check fstab Entries

    The entries in the file are checked for completeness and consistency. All valid partitions are mounted.

    Check Package Database

    This checks whether all packages necessary for the operation of a minimal installation are present. While it is optionally possible to also analyze the base packages, this takes a long time because of their vast number.

    Check Boot Loader Configuration

    The boot loader configuration of the installed system (GRUB or LILO) is checked for completeness and coherence. Boot and root devices are examined and the availability of the initrd modules is checked.

  6. Whenever an error is encountered, the procedure stops and a dialog opens outlining the details and possible solutions.

    Read the screen messages carefully before accepting the proposed fix. If you decide to decline a proposed solution, your system remains unchanged.

  7. After the repair process has been terminated successfully, click OK and Finish and remove the installation media. The system automatically reboots.

36.6.4.1.2 Customized Repair

To launch the Customized Repair mode and selectively check certain components of your installed system, proceed as follows:

  1. Insert the installation medium of SUSE Linux Enterprise Server into your DVD drive.

  2. Reboot the system.

  3. At the boot screen, select Repair Installed System.

  4. Confirm the license agreement and click Next.

  5. Select Customized Repair.

    Choosing Customized Repair shows a list of test runs that are all marked for execution at first. The total range of tests matches that of automatic repair. If you already know where no damage is present, unmark the corresponding tests. Clicking Next starts a narrower test procedure that probably has a significantly shorter running time.

    Not all test groups can be applied individually. The analysis of the fstab entries is always bound to an examination of the file systems, including existing swap partitions. YaST automatically resolves such dependencies by selecting the smallest number of necessary test runs. YaST does not support encrypted partitions. If you have one, YaST informs you about it.

  6. Whenever an error is encountered, the procedure stops and a dialog opens outlining the details and possible solutions.

    Read the screen messages carefully before accepting the proposed fix. If you decide to decline a proposed solution, your system remains unchanged.

  7. After the repair process has been terminated successfully, click OK and Finish and remove the installation media. The system automatically reboots.

36.6.4.1.3 Expert Tools

If you are knowledgeable with SUSE Linux Enterprise Server and already have a very clear idea of what needs to be repaired in your system, directly apply the tools, skipping the system analysis.

To make use of the Expert Tools feature of the YaST System Repair module, proceed as follows:

  1. Insert the installation medium of SUSE Linux Enterprise Server into your DVD drive.

  2. Reboot the system.

  3. At the boot screen, select Repair Installed System.

  4. Confirm the license agreement and click Next.

  5. Select Expert Tools and choose a repair option.

  6. After the repair process has been terminated successfully, click OK and Finish and remove the installation media. The system automatically reboots.

The Expert Tools provides the following options to repair your faulty system:

Install New Boot Loader

This starts the YaST boot loader configuration module. Find details in Section 11.2, “Configuring the Boot Loader with YaST”.

Boot Installed System

Try to boot an already-installed Linux system.

Start Partitioning Tool

This starts the expert partitioning tool in YaST.

Repair File System

This checks the file systems of your installed system. You are first offered a selection of all detected partitions and can then choose the ones to check.

Recover Lost Partitions

It is possible to attempt to reconstruct damaged partition tables. A list of detected hard disks is presented first for selection. Clicking OK starts the examination. This can take a while depending on the speed of your computer and the size and speed of the hard disk.

Important
Important: Reconstructing a Partition Table

The reconstruction of a partition table is tricky. YaST attempts to recognize lost partitions by analyzing the data sectors of the hard disk. The lost partitions are added to the rebuilt partition table when recognized. This is, however, not successful in all imaginable cases.

Save System Settings to Floppy

This option saves important system files to a floppy disk. If one of these files becomes damaged, it can be restored from disk.

Verify Installed Software

This checks the consistency of the package database and the availability of the most important packages. Any damaged installed packages can be reinstalled with this tool.

36.6.4.2 Using the Rescue System

SUSE Linux Enterprise Server contains a rescue system. The rescue system is a small Linux system that can be loaded into a RAM disk and mounted as root file system, allowing you to access your Linux partitions from the outside. Using the rescue system, you can recover or modify any important aspect of your system:

  • Manipulate any type of configuration file.

  • Check the file system for defects and start automatic repair processes.

  • Access the installed system in a change root environment.

  • Check, modify, and reinstall the boot loader configuration.

  • Recover from a badly installed device driver or unusable kernel.

  • Resize partitions using the parted command. Find more information about this tool at the GNU Parted website http://www.gnu.org/software/parted/parted.html.

The rescue system can be loaded from various sources and locations. The simplest option is to boot the rescue system from the original installation medium:

  1. Insert the installation medium into your DVD drive.

  2. Reboot the system.

  3. At the boot screen, press F4 and choose DVD-ROM. Then choose Rescue System from the main menu.

  4. Enter root at the Rescue: prompt. A password is not required.

If your hardware setup does not include a DVD drive, you can boot the rescue system from a network source. The following example applies to a remote boot scenario—if using another boot medium, such as a DVD, modify the info file accordingly and boot as you would for a normal installation.

  1. Enter the configuration of your PXE boot setup and add the lines install=protocol://instsource and rescue=1. If you need to start the repair system, use repair=1 instead. As with a normal installation, protocol stands for any of the supported network protocols (NFS, HTTP, FTP, etc.) and instsource for the path to your network installation source.

  2. Boot the system using Wake on LAN, as described in Section 14.3.7, “Wake on LAN”.

  3. Enter root at the Rescue: prompt. A password is not required.

Once you have entered the rescue system, you can make use of the virtual consoles that can be reached with AltF1 to AltF6.

A shell and many other useful utilities, such as the mount program, are available in the /bin directory. The sbin directory contains important file and network utilities for reviewing and repairing the file system. This directory also contains the most important binaries for system maintenance, such as fdisk, mkfs, mkswap, mount, mount, init, and shutdown, and ifconfig, ip, route, and netstat for maintaining the network. The directory /usr/bin contains the vi editor, find, less, and ssh.

To see the system messages, either use the command dmesg or view the file /var/log/messages.

36.6.4.2.1 Checking and Manipulating Configuration Files

As an example for a configuration that might be fixed using the rescue system, imagine you have a broken configuration file that prevents the system from booting properly. You can fix this using the rescue system.

To manipulate a configuration file, proceed as follows:

  1. Start the rescue system using one of the methods described above.

  2. To mount a root file system located under /dev/sda6 to the rescue system, use the following command:

    mount /dev/sda6 /mnt

    All directories of the system are now located under /mnt

  3. Change the directory to the mounted root file system:

    cd /mnt
  4. Open the problematic configuration file in the vi editor. Adjust and save the configuration.

  5. Unmount the root file system from the rescue system:

    umount /mnt
  6. Reboot the machine.

36.6.4.2.2 Repairing and Checking File Systems

Generally, file systems cannot be repaired on a running system. If you encounter serious problems, you may not even be able to mount your root file system and the system boot may end with a kernel panic. In this case, the only way is to repair the system from the outside. It is strongly recommended to use the YaST System Repair for this task (see Section 36.6.4.1, “Using YaST System Repair” for details). However, if you need to do a manual file system check or repair, boot the rescue system. It contains the utilities to check and repair the btrfs, ext2, ext3, ext4, reiserfs, xfs, dosfs, and vfat file systems.

36.6.4.2.3 Accessing the Installed System

If you need to access the installed system from the rescue system, you need to do this in a change root environment. For example, to modify the boot loader configuration, or to execute a hardware configuration utility.

To set up a change root environment based on the installed system, proceed as follows:

  1. First mount the root partition from the installed system and the device file system (change the device name to your current settings):

    mount /dev/sda6 /mnt
    mount --bind /dev /mnt/dev
  2. Now you can change root into the new environment:

    chroot /mnt
  3. Then mount /proc and /sys:

    mount /proc
    mount /sys
  4. Finally, mount the remaining partitions from the installed system:

    mount -a
  5. Now you have access to the installed system. Before rebooting the system, unmount the partitions with umount -a and leave the change root environment with exit.

Warning
Warning: Limitations

Although you have full access to the files and applications of the installed system, there are some limitations. The kernel that is running is the one that was booted with the rescue system, not with the change root environment. It only supports essential hardware and it is not possible to add kernel modules from the installed system unless the kernel versions are exactly the same. Always check the version of the currently running (rescue) kernel with uname -r and then find out if a matching subdirectory exists in the /lib/modules directory in the change root environment. If yes, you can use the installed modules, otherwise you need to supply their correct versions on other media, such as a USB stick. Most often the rescue kernel version differs from the installed one — then you cannot simply access a sound card, for example. It is also not possible to start a graphical user interface.

Also note that you leave the change root environment when you switch the console with AltF1 to AltF6.

36.6.4.2.4 Modifying and Reinstalling the Boot Loader

Sometimes a system cannot boot because the boot loader configuration is corrupted. The start-up routines cannot, for example, translate physical drives to the actual locations in the Linux file system without a working boot loader.

To check the boot loader configuration and reinstall the boot loader, proceed as follows:

  1. Perform the necessary steps to access the installed system as described in Section 36.6.4.2.3, “Accessing the Installed System”.

  2. Check whether the following files are correctly configured according to the GRUB configuration principles outlined in Chapter 11, The Boot Loader GRUB and apply fixes if necessary.

    • /etc/grub.conf

    • /boot/grub/device.map

    • /boot/grub/menu.lst

    • /etc/sysconfig/bootloader

  3. Reinstall the boot loader using the following command sequence:

    grub --batch < /etc/grub.conf
  4. Unmount the partitions, log out from the change root environment, and reboot the system:

    umount -a
    exit
    reboot
36.6.4.2.5 Fixing Kernel Installation

A kernel update may introduce a new bug which can impact the operation of your system. For example a driver for a piece of hardware in your system may be faulty, which prevents you from accessing and using it. In this case, revert to the last working kernel (if available on the system) or install the original kernel from the installation media.

Tip
Tip: How to Keep Last Kernels after Update

To prevent failures to boot after a faulty kernel update, use the kernel multiversion feature and tell libzypp which kernels you want to keep after the update.

For example to always keep the last two kernels and the currently running one, add

multiversion.kernels = latest,latest-1,running

to the /etc/zypp/zypp.conf file.

A similar case is when you need to reinstall or update a broken driver for a device not supported by SUSE Linux Enterprise Server. For example when a hardware vendor uses a specific device, such as a hardware RAID controller, which needs a binary driver to be recognized by the operating system. The vendor typically releases a Driver Update Disk with the fixed or updated version of the required driver.

In both cases you need to access the installed system in the rescue mode and fix the kernel related problem, otherwise the system may fail to boot correctly:

  1. Boot from the SUSE Linux Enterprise Server installation media.

  2. If you are recovering after a faulty kernel update, skip this step. If you need to use a driver update disk (DUD), press F6 to load the driver update after the boot menu appears, and choose the path or URL to the driver update and confirm with Yes.

  3. Choose Rescue System from the boot menu and press Enter. If you chose to use DUD, you will be asked to specify where the driver update is stored.

  4. Enter root at the Rescue: prompt. A password is not required.

  5. Manually mount the target system and change root into the new environment. For more information, see Section 36.6.4.2.3, “Accessing the Installed System”.

  6. If using DUD, install/reinstall/update the faulty device driver package. Always make sure the installed kernel version exactly matches the version of the driver you are installing.

    If fixing faulty kernel update installation, you can install the original kernel from the installation media with the following procedure.

    1. Identify your DVD device with hwinfo --cdrom and mount it with mount /dev/sr0 /mnt.

    2. Navigate to the directory where your kernel files are stored on the DVD, for example cd /mnt/suse/x86_64/.

    3. Install required kernel-*, kernel-*-base, and kernel-*-extra packages of your flavor with the rpm -i command.

    4. After the installation finishes, check that a new menu entry relevant for the newly installed kernel was added to the boot loader configuration file (/boot/grub/menu.lst for grub).

  7. Update configuration files and reinitialize the boot loader if needed. For more information, see Section 36.6.4.2.4, “Modifying and Reinstalling the Boot Loader”.

  8. Remove any bootable media from the system drive and reboot.

36.7 IBM System z: Using initrd as a Rescue System

If the kernel of the SUSE® Linux Enterprise Server for IBM System z is upgraded or modified, it is possible to reboot the system accidentally in an inconsistent state, so standard procedures of IPLing the installed system fail. This most commonly occurs if a new or updated SUSE Linux Enterprise Server kernel has been installed and the zipl program has not been run to update the IPL record. In this case, use the standard installation package as a rescue system from which the zipl program can be executed to update the IPL record.

36.7.1 IPLing the Rescue System

Important
Important: Making the Installation Data Available

For this method to work, the SUSE Linux Enterprise Server for IBM System z installation data must be available. For details, refer to Section 4.2.1, “Making the Installation Data Available”. Additionally, you need the channel number of the device and the partition number within the device that contains the root file system of the SUSE Linux Enterprise Server installation.

First, IPL the SUSE Linux Enterprise Server for IBM System z installation system as described in Section 4.2, “Preparing for Installation”. A list of choices for the network adapter to use is then presented.

Select Start Installation or System then Start Rescue System to start the rescue system. Depending on the installation environment, you now must specify the parameters for the network adapter and the installation source. The rescue system is loaded and the following login prompt is shown at the end:

Skipped services in runlevel 3:  nfs nfsboot

Rescue login:

You can now log in as root without a password.

36.7.2 Configuring Disks

In this state, no disks are configured. You need to configure them before you can proceed.

Procedure 36.8: Configuring DASDs
  1. Configure DASDs with the following command:

    dasd_configure 0.0.0150 1 0

    0.0.0150 is the channel to which the DASD is connected. The 1 means activate the disk (a 0 at this place would deactivate the disk). The 0 stands for no DIAG mode for the disk (a 1 here would enable DAIG access to the disk).

  2. Now the DASD is online (check with cat /proc/partitions) and can used for subsequent commands.

Procedure 36.9: Configuring a zFCP Disk
  1. To configure a zFCP disk, it is necessary to first configure the zFCP adapter. Do this with the following command:

    zfcp_host_configure 0.0.4000 1

    0.0.4000 is the channel to which the adapter is attached and 1 stands for activate (a 0 here would deactivate the adapter).

  2. After the adapter is activated, a disk can be configured. Do this with the following command:

    zfcp_disk_configure 0.0.4000 1234567887654321 8765432100000000  1

    0.0.4000 is the previously-used channel ID, 1234567887654321 is the WWPN (World wide Port Number), and 8765432100000000 is the LUN (logical unit number). The 1 stands for activating the disk (a 0 here would deactivate the disk).

  3. Now the zFCP disk is online (check with cat /proc/partitions) and can used for subsequent commands.

36.7.3 Mounting the Root Device

If all needed disks are online, you should now be able to mount the root device. Assuming that the root device is on the second partition of the DASD device (/dev/dasda2), the corresponding command is mount /dev/dasda2 /mnt.

Important
Important: File System Consistency

If the installed system has not been shut down properly, it may be advisable to check the file system consistency prior to mounting. This prevents any accidental loss of data. Using this example, issue the command fsck /dev/dasda2 to ensure that the file system is in a consistent state.

By just issuing the command mount, it is possible to check whether the file system could be mounted correctly.

Example 36.1: Output of the Mount Command
SuSE Instsys suse:/ # mount
shmfs on /newroot type shm (rw,nr_inodes=10240)
devpts on /dev/pts type devpts (rw)
virtual-proc-filesystem on /proc type proc (rw)
/dev/dasda2 on /mnt type reiserfs (rw)

36.7.4 Changing to the Mounted File System

For the zipl command to read the configuration file from the root device of the installed system and not from the rescue system, change the root device to the installed system with the chroot command:

Example 36.2: chroot to the Mounted File System
SuSE Instsys suse:/ # cd /mnt 
SuSE Instsys suse:/mnt # chroot /mnt

36.7.5 Executing zipl

Now execute zipl to rewrite the IPL record with the correct values:

Example 36.3: Installing the IPL Record with zipl
sh-2.05b# zipl 
building bootmap : /boot/zipl/bootmap 
adding Kernel Image : /boot/kernel/image located at 0x00010000 
adding Ramdisk : /boot/initrd located at 0x00800000 
adding Parmline : /boot/zipl/parmfile located at 0x00001000 
Bootloader for ECKD type devices with z/OS compatible layout installed. 
Syncing disks.... 
...done

36.7.6 Exiting the Rescue System

To exit the rescue system, first leave the shell opened by the chroot command with exit. To prevent any loss of data, flush all unwritten buffers to disk with the sync command. Now change to the root directory of the rescue system and unmount the root device of SUSE Linux Enterprise Server for IBM System z installation.

Example 36.4: Unmounting the File System
SuSE Instsys suse:/mnt # cd / 
SuSE Instsys suse:/ # umount /mnt

Finally, halt the rescue system with the halt command. The SUSE Linux Enterprise Server system can now be IPLed as described in Section 6.15.1, “IBM System z: IPLing the Installed System”.

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