To repair your Ubuntu GRUB, you need Ubuntu LiveCD, boot from this CD, and open a terminal. Be a root, by typing “sudo su” and enter your password.
Find the partition which your Ubuntu system is installed.
# fdisk -l
On my machine, my Ubuntu partition is on /dev/sda3, so i’ll use this for example.
Create a mountpoint for this:
# mkdir /media/rootgrub
# mount /dev/sda3 /media/rootgrub
Check if your partition is the correct partition
# ls /media/rootgrub
if the output is not like this, then you have the wrong partition
bin dev home lib mnt root srv usr boot etc initrd lib64 opt sbin sys
var cdrom initrd.img media proc selinux tmp vmlinuz
unmount the partition if have the wrong one, then mount the others. To make sure you have the correct partition, run ls /media/root/boot, which should output something like this :
config-2.6.18-3-686 ¬ ¬ initrd.img-2.6.18-3-686.bak ¬ ¬ System.map-2.6.18-3-686
grub lost+found ¬ ¬ ¬ ¬ ¬ vmlinuz-2.6.18-3-686 ¬ ¬ ¬ ¬ ¬ ¬ initrd.img-2.6.18-3-686
Now when everything is ok, install the Grub:
# sudo grub-install –root-directory=/media/rootgrub¬ /dev/sda
If you have some warning, try this:
# sudo grub-install –root-directory=/media/rootgrub¬ /dev/sda –recheck
Change /dev/sda to other partition you want to install Grub on. If all goes fine, you will see the output like this:
Installation finished. No error reported. This is the contents of the device map /boot/grub/device.map. Check if this is correct or not. If any of the lines is incorrect, fix it and re-run the script `grub-install’.
Restart to your harddrive (not to LiveCD) and see, your GRUB should be AUTOMAGICALLY appear!