How to implement a rescue system on a SUSE Linux Enterprise Server 12

This document (7018607) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 12

Situation

The aim is to implement a disk or ISO based rescue system that can be booted from the grub2 boot screen in case the system experiences problems.

Resolution

Scenario 1: Boot the rescue media from local disk structure.

Assumption: It is desired to have the files from rescue media in /boot. /dev/sda1 is mounted there.

1. Mount the SLE ISO to /mnt
2. cd /mnt
3. Copy the following content to a directory (e.g /boot). The following script may help with the given task:

#!/bin/bash
set -x

DEST=/boot
mkdir -p /$DEST/media/boot/x86_64/loader
for i in \
content \
content.asc \
boot/x86_64/loader/initrd \
boot/x86_64/loader/linux \
boot/x86_64/rescue \
boot/x86_64/common \
boot/x86_64/config \
boot/x86_64/cracklib-dict-full.rpm
do
cp -av /mnt/$i /$DEST/media/$i
done
set +x

4. Create a new grub2 boot entry in /etc/grub.d/40_custom:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.

menuentry "Rescue with FS Path: /boot" --class sles --class gnu-linux --class gnu --class os {
load_video
set gfxpayload=keep
insmod gzio
insmod part_msdos
insmod btrfs
insmod ext2
insmod lvm
set root=(hd1)
#set root=(lvm/system-lvboot)
set loader=(hd1)
linux $loader/media/boot/x86_64/loader/linux rescue=1 install=hd:/media?device=sdb* keytable=de namescheme= splash=silent vga=0x318 panic=10 linemode=1 linuxrc.debug=4,trace
initrd $loader/media/boot/x86_64/loader/initrd

}

5. Activate the new boot loader configuration:

grub2-mkconfig -o /boot/grub2/grub.cfg

6. Reboot and test

Scenario 2: Boot the rescue media from an ISO from disk

1. Mount your SLE ISO to /mnt
2. Copy the following content to a local directory of your need (e.g /tmp)

#!/bin/bash
set -x

DEST=/tmp
mkdir -p /$DEST/media/boot/x86_64/loader
for i in \
content \
content.asc \
boot/x86_64/loader/initrd \
boot/x86_64/loader/linux \
boot/x86_64/rescue \
boot/x86_64/common \
boot/x86_64/config \
boot/x86_64/cracklib-dict-full.rpm
do
cp -av /mnt/$i /$DEST/media/$i
done
set +x

3. Create an ISO file from the created directory

cd /tmp
mkisofs -o /boot/media.iso -l media

4. Add a new grub2 boot entry in /etc/grub.d/40_custom

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.

menuentry "Rescue with ISO" --class sles --class gnu-linux --class gnu --class os {
load_video
set gfxpayload=keep
insmod gzio
insmod part_msdos
insmod btrfs
insmod ext2
insmod lvm

set isofile=(hd0,1)/media.iso
loopback loop $isofile
set root=(hd0,1,msdos2)

linux (loop)/boot/x86_64/loader/linux rescue=1 install=hd:/media.iso keytable=de namescheme= splash=silent vga=0x318 panic=10 linemode=1 linuxrc.debug=4,trace
initrd (loop)/boot/x86_64/loader/initrd

}

Cause

Additional Information

Disclaimer

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