Grub Rescue

GRUB RESCUE

Grub Rescue commands

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.