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13.6 Data Problems
Data problems are when the machine might or might 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 a system state from
before your system failed. openSUSE 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.
13.6.1 Backing Up Critical Data
System backups can be easily managed using the YaST System Backup
module:
-
As root, start YaST and select .
-
Create a backup profile holding all details needed for the backup,
filename of the archive file, scope, and type of the backup:
-
Select .
-
Enter a name for the archive.
-
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.
-
Determine the archive type and click .
-
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 to enter a dialog for the backup of
entire hard disk areas. Currently, this option only applies to the
Ext2 file system.
-
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 .
-
Once you have finished the profile settings, you can start the backup
right away with 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:
-
Select from the menu.
-
Select .
-
Determine the backup frequency. Choose ,
, or .
-
Determine the backup start time. These settings depend on the backup
frequency selected.
-
Decide whether to keep old backups and how many should be kept. To
receive an automatically generated status message of the backup
process, check .
-
Click to apply your settings and have the first
backup start at the time specified.
13.6.2 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.
-
Start .
-
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 .
The following dialog displays a summary of the archive properties,
such as the filename, date of creation, type of backup, and optional
comments.
-
Review the archived content by clicking . Clicking returns you to the
dialog.
-
opens a dialog in which to fine-tune
the restore process. Return to the dialog by clicking .
-
Click to open the view of packages to restore.
Press to restore all files in the archive or
use the various , , and buttons to
fine-tune your selection. Only use the option if the RPM database is corrupted or deleted
and this file is included in the backup.
-
After you click , the backup is restored.
Click to leave the module after the restore
process is completed.
13.6.3 Recovering a Corrupted System
There are several reasons why a system could fail to come up and run
properly. A corrupted file system after a system crash, corrupted
configuration files, or a corrupted boot loader configuration are the most
common ones.
openSUSE offers two different methods to cope with these
situations. You can either use the YaST System Repair functionality or
boot the rescue system. The following sections cover both flavors of
system repair.
Using YaST System Repair
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 severeness 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
. An extensive automated check will
be performed on all components of your installed system. For a
detailed description of this procedure, refer to
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 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 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 respective component. For
details, refer to
Expert Tools.
Choose one of the repair modes as described above and proceed with the
system repair as outlined in the following sections.
Automatic Repair
To start the automatic repair mode of YaST System Repair, proceed as
follows:
-
Insert the installation medium of openSUSE into your DVD drive.
-
Reboot the system.
-
On the boot screen, select .
-
Confirm the license agreement and click .
-
Select .
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 13-2. 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
also to 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.
-
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.
-
After the repair process has been terminated successfully, click
and and remove the
installation media. The system automatically reboots.
Customized Repair
To launch the mode and selectively
check certain components of your installed system, proceed as follows:
-
Insert the installation medium of openSUSE into your DVD drive.
-
Reboot the system.
-
At the boot screen, select .
-
Confirm the license agreement and click .
-
Select .
Choosing 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
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.
-
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.
-
After the repair process has been terminated successfully, click
and and remove the
installation media. The system automatically reboots.
Expert Tools
If you are knowledgeable with openSUSE 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 feature of the
YaST System Repair module, proceed as follows:
-
Insert the installation medium of openSUSE into your DVD drive.
-
Reboot the system.
-
At the boot screen, select .
-
Confirm the license agreement and click .
-
Select and choose a repair option.
-
After the repair process has been terminated successfully, click
and and remove the
installation media. The system automatically reboots.
The provides the following options to
repair your faulty system:
-
-
This starts the YaST boot loader configuration module. Find details
in Section 15.2, Configuring the Boot Loader with YaST, (↑ Reference ).
-
-
This starts the expert partitioning tool in YaST.
-
-
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.
-
-
It is possible to attempt to reconstruct damaged partition tables. A
list of detected hard disks is presented first for selection.
Clicking starts the examination. This can take
a while depending on the processing power and size of the hard disk.
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.
-
-
This option saves important system files to a floppy disk. If one of
these files becomes damaged, it can be restored from disk.
-
-
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.
Using the Rescue System
openSUSE 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.
-
Resize partitions using the parted command. Find more information about
this tool at the Web site of GNU Parted
(https://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:
-
Insert the installation medium into your DVD drive.
-
Reboot the system.
-
At the boot screen, press F4 and choose
. Then choose from the main menu.
-
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 (including the
openSUSE FTP server). 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.
-
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.
-
Boot the system using Wake on LAN , as described in
Section 1.3.7, Wake on LAN, (↑ Reference ).
-
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
Alt+F1 to
Alt+F6.
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.
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:
-
Start the rescue system using one of the methods described above.
-
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
-
Change the directory to the mounted root file system:
cd /mnt
-
Open the problematic configuration file in the vi editor. Adjust and
save the configuration.
-
Unmount the root file system from the rescue system:
umount /mnt
-
Reboot the machine.
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 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 ext2, ext3,
reiserfs, xfs,
dosfs, and vfat file systems.
Accessing the Installed System
If you need to access the installed system from the rescue system to,
for example, modify the boot loader configuration, or to execute a
hardware configuration utility, you need to do this in a change
root environment.
To set up a change root environment based on the
installed system, proceed as follows:
-
First mount the root partition from the installed system and the
device file system:
mount /dev/sda6 /mnt
mount --bind /dev /mnt/dev
-
Now you can change root into the new environment:
chroot /mnt
-
Then mount /proc and /sys:
mount /proc
mount /sys
-
Finally, mount the remaining partitions from the installed system:
mount -a
-
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: 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. 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 (which is unlikely). So you cannot 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
Alt+F1 to
Alt+F6.
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:
-
Perform the necessary steps to access the installed system as
described in Accessing the Installed System.
-
Check whether the following files are correctly configured according
to the GRUB configuration principles outlined in
Section 15.0, The Boot Loader, (↑ Reference ).
-
/etc/grub.conf
-
/boot/grub/device.map
-
/boot/grub/menu.lst
Apply fixes to the device mapping (device.map) or
the location of the root partition and configuration files, if
necessary.
-
Reinstall the boot loader using the following command sequence:
grub --batch < /etc/grub.conf
-
Unmount the partitions, log out from the change root
environment, and reboot the system:
umount -a
exit
reboot
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