How to Chroot in Rescue Mode

This document (7018126) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server 11

Situation

The system is unable to boot and the only way to run the necessary fix is to chroot into it from rescue mode on the media.

Resolution

1. First boot the system into Rescue Mode from the media. For best results use media that matches the version and service pack of the system.

2. Once it's finished loading, log in as root.

3. Mount the root partition or logical volume to /mnt

mount /dev/<device name> /mnt

If it's not known where the root file system is, it needs to be guessed until found by mounting each possibility and checking its contents. Run the following command to list all available partitions:

cat /proc/partitions

List all available logical volumes with this command:

lvdisplay

After mounting each one check its contents by listing the mounted directory. For example if mounted to /mnt run:

ls /mnt

Some directories that should be listed to verify it is a root file system are /root /boot and /home.

4. Once mounted use the following for-loop to rbind the virtual file systems:

for i in proc sys dev; do mount --rbind /$i /mnt/$i ; done

Alternatively, mount them each separately rather than using the for-loop:

mount --rbind /proc /mnt/proc
mount --rbind /sys /mnt/sys
mount --rbind /dev /mnt/dev

5. After the root file system and virtual file systems are mounted run this command to chroot in:

chroot /mnt

After chrooted in it is a best-practice to run this command to make sure all other necessary partitions are also mounted:

mount -a

If the initrd has been damaged, this can be recreated with:

mkinitrd

Cause

System does no longer boot.
There are several possible causes for that behavior.

Additional Information

Keep in mind that a chrooted system was not booted.

This means that services aren't running upon chroot into the system.

In SLE 12 systemd does not allow services to be started within the chrooted environment. Executable commands, so long as they don't rely on those services, should still work though. If you absolutely need to have a systemd service running in rescue mode look into systemd-nspawn

When using multipath with lvm, you should start multipathd before using lvm. If you do not, lvm may not detect the physical volumes needed to mount filesystems due to the lvm filter.

Disclaimer

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