It may occur that Grub Rescue prompt appears after installing Ubuntu or after an upgrade of grub and screen is showing
grub rescue>
unknown filesystem
or anything similar to that.
Then Ubuntu grub rescue or restore has to done. It can be done through Ubuntu Desktop CD or a bootable USB pen Drive.
This article will show how to do Ubuntu grub rescue with screen shots using Ubuntu Desktop CD. These screenshots of Ubuntu grub rescue has been taken on Ubuntu 11.04. The very same method can be used to repair grub mint Debian or Later versions of Ubuntu.
NOTE: You will get /usr/sbin/grub-probe: error: cannot stat 'aufs' error if you didn't follow the commands listed below. Specifically you did not do chroot,
ie sudo chroot /mnt.
For Ubuntu grub rescue follow these steps:
1.Boot from the Ubuntu Desktop live CD or Pendrive.
Select Try Ubuntu
2.In Live Desktop session open terminal.
Applications , Accessories , Terminal.
(in ubuntu 12.04 precise pangolin,click dash and type terminal)
3. In Terminal type sudo fdisk -l .
It will display all partition of the disk.
The partition which have Linux under System column is your drive in which Ubuntu Linux is installed. In screenshot Ubuntu partition drive is /dev/sda11.
4. Mount the Ubuntu partition drive
sudo mount /dev/sdXX /mnt (example 'sudo mount /dev/sda11 /mnt' ,don't miss the spaces.)
5.Only if you have a separate boot partition:
sudo mount /dev/sdYY /mnt/boot.
6. Mount the virtual file systems:
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
7. To ensure that only the grub utilities from the Live CD get executed, mount /usr
sudo mount --bind /usr/ /mnt/usr
sudo chroot /mnt
8. If there is no /boot/grub/grub.cfg or it's not correct, create one using
update-grub
or
update-grub2
9.Now re-install Grub
grub-install /dev/sdX
(eg. grub-install /dev/sda. Do not specify the partition number.
10. Verify the install
sudo grub-install --recheck /dev/sdX
11. Exit chroot : CTRL-D on keyboard.
12. Un-mount virtual file-systems:
sudo umount /mnt/dev
sudo umount /mnt/proc
sudo umount /mnt/sys
If you mounted a separate /boot partition:
sudo umount /mnt/boot
13. Unmount the LiveCD's /usr directory:
sudo umount /mnt/usr
14. Unmount last device:
sudo umount /mnt
15. Reboot.
sudo reboot.
NOTE: If you are getting /usr/sbin/grub-probe: error: cannot stat 'aufs'
error then the possible reason is that you didn't follow the commands
listed above. Specifically you did not do chroot,
ie sudo chroot /mnt.
Follow the above steps correctly and you are done.
