52.7 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.
52.7.1 IPLing the Rescue System
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 “Making the Installation Data Available” (Chapter “Preparing for Installation”, ↑Architecture-Specific Information) from Architecture-Specific Information. 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
the Architecture-Specific Information manual. A list of choices for the network adapter to use is then
presented.
Select 4 then 3
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 login as root without a password.
52.7.3 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: 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 52-1
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)
52.7.4 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 52-2
chroot to the Mounted File System
SuSE Instsys suse:/ # cd /mnt
SuSE Instsys suse:/mnt # chroot /mnt
52.7.5 Executing zipl
Now execute zipl to rewrite the IPL record with the
correct values:
Example 52-3
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
52.7.6 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 52-4
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 3.9.10,
IBM System z: IPLing the Installed System.