How To Rescue Linux From The Grub Prompt

on February 27, 2012 in Linux

Boot into single user mode from grub

Ever encounter the dreaded Linux server that does not boot back up after a reboot? Here is how to rescue a Linux server from the grub prompt or from a rescue disk and mount the file systems so you can at least determine what went wrong.

Method 1: Boot To Single User

You will need the root password for this method

Press ‘e’ when GRUB displays
Press ‘e’ again on kernel line
Add “single” to the end of the kernel line
Press ‘b’ to boot

Method 2: Use Rescue Mode

You will NOT need the root password for this method.

If you are using HP ILO or Dell DRAC then you can mount an ISO image of the boot disk as a virtual media CD rom.

Reset System and boot from CD Rom into rescue mode.

NOTE: Rescue mode does not do anything with LVM by default. So you will need to activate the volume groups.

#lvm vgscan
#lvm vgchange -ay
#lvm lvs
mount /dev/mapper/system-root /tmp/root
# now you can edit whatever you need to get your server running again. For example change the root password.