Using the rescue system (advanced)

From openSUSE

Situation

You need to mount all your file systems or reinstall your boot loader, but cannot or choose not to do so by starting the computer in the normal fashion.

Procedure

Start the rescue system

• Boot from the openSUSE 11.1 CD or DVD.
• Select Rescue System
• Login as "root" (there's no password)

Listing the file systems

First, we need to a list of storage devices with filesystems to mount. We can usually just ask the kernel what partitions it is aware of:

cat /proc/partitions

To ask the hard drive for a list of partitions, which helps because the partition table also may include useful partition type information, perform the following. The device /dev/sda is most typical for modern computers as the primary hard drive. On older non-SATA systems, it is usually /dev/hda. If there are multiple drives, it is harmless to query a device using this method when you don't know for sure if it is the correct device. Just don't forget the lowercase L option which only lists and doesn't put you into partition edit mode.

fdisk -l /dev/sda

• Note which partitions are mounted at which points in your filesystem. For instance, most Linux users will have at least a swap and root (/) partition. Some will have a separate /home, /usr or /var partition. If you don't know which partitions are which by size or order, you might have to mount them experimentally to find which are which.

For the sake of simplicity in this article, we'll assume the partition table looks like this:

Unlock encrypted partitions

If you are using encrypted partitions with LUKS, you will need to unlock them before using them. To do this, you will need to use cryptsetup.

cryptsetup luksOpen /dev/sda3 root

In the above case, your root partition device would then be /dev/mapper/root.

Make the swap available

Mounting the swap space allows us more memory space and better control over physical memory.

swapon /dev/sda2

Mount your file systems

Mount root file system

mount /dev/sda3 /mnt

Mount boot file system, if separate

mount /dev/sda1 /mnt/boot

Bind mount temporary file systems

mount --bind /dev /mnt/dev
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys

Mount other partitions

mount /dev/sda4 /mnt/home

Prepare and enter the new root

Copy your mounts and DNS resolution files

cp /etc/mtab /mnt/etc/mtab
cp /etc/resolv.conf /mnt/etc/resolv.conf

Make the mount point the new root

chroot /mnt /bin/bash

Get work done in your file system

At this point, you should have an entirely usable file system that should closely match your normal file system. It should be possible to mount other media and copy files or re-install the boot loader.

Optional: Reload the boot loader

Reload boot loader, if desired

• Launch yast
• Navigate to System > Boot Loader
• Select boot loader installation
• Check Boot Loader Location > Boot from Master Boot Record

Cleaning up

Once done with your file system, you can exit and reboot.

• Exit the new root and unmount all your filesytems.

exit
umount /mnt/boot
umount /mnt/dev
umount /mnt/proc
umount /mnt/sys
umount /mnt/home
umount /mnt

If you get an error with the last command, you may need to unmount other file systems. Use "mount" to see what filesystems are mounted.

Then

reboot

See Also

• Determining which partition is which
• SDB:Use of the Rescue System