Ubuntu Wiki

Task name: Re-install GRUB on the MBR

Description: After installing another OS I lost the mbr on my HD (hda with ubuntu on hda7), here is the solution that I found to work.

Procedure:

• Boot the Ubuntu LIVE CD
• open a console, and change to user root with

su root

• Make a temp dir to mount the ubuntu partition with :

mkdir /mnt/hda7

• Mount the drive with :

mount -t ext2 /dev/hda7 /hda7

• Chroot to the mounted system with :

chroot /dev/hda7

• Run grub, then :

grub> root (<tab>

where <tab> is an actual TAB which returns the hd that grub recognises, in my case hd0 hd1 hd2 then :

grub> root (hd0,5)

# in my case the hda7 partition is recognized by grub as (hd0,5)

grub> setup (hd0,5)

grub> exit

then reboot and it works...