Recovering from 'grub rescue>' crash

Question

I did a dumb thing... I forgot that Ubuntu 10.04 (Lucid) switched to Grub2 which puts a ton of *.mod files (kernel modules) in /boot/grub. I thought they were soundtrack files put there erroneously and moved them. Needless to say, the next reboot was traumatic. I was presented with something I had no memory of ever seeing... a 'grub rescue>' prompt.

With the help of how-to-fix-error-unknown-filesystem-grub-rescue however, I was able to recover...

• Discovered that Grub Rescue does not have 'cd', 'cp' or any other filesystem commands except its own variation of 'ls'.

• So first I had to find the partition with the /boot directory containing vmlinuz... and other boot image files... (failed attempts not shown)

  grub rescue>  ls  
  (hd0,4) (hd0,3) (hd0,2) (hd0,1)  
   grub rescue>  ls (hd0,2)/boot
  ... grub ... initrd.img-2.6.32-33-generic ... vmlinuz-2.6.32-33-generic 
  

• Then manually boot from 'grub rescue>' prompt (no command history either!)...

  grub rescue>  set root=(hd0,2)/boot  
  grub rescue>  insmod linux  
  grub rescue>  linux (hd0,2)/boot/vmlinuz-2.6.32-33-generic  
  grub rescue>  initrd (hd0,2)/boot/initrd.img-2.6.32-33-generic  
  grub rescue>  boot  
  

• This boots and crashes to the BusyBox prompt which DOES have some rudimentary filesystem commnds.

• Then I moved the *.mod files back to the /boot/grub directory...

  busybox>  cd /boot  
  busybox>  mv mod/* grub
  busybox>  reboot
  

• The reboot was successful but that was a lot of work.

Is there an easier way?

Answer 1

No. I think you pretty much found the easiest way to recover from the state of your system using grub rescue; it is a very minimalistic system giving just enough capability to boot the system.

BTW, I believe you must have found the .mod files and executed insmod linux or the linux command would have failed.

The only other way, as mentioned, would be to boot a Live CD and reinstall grub2 after chroot'ing to the 'broken' system.

Answer 2

General & basic help to boot errors like

GRUB loading stage 1.5 error 15 (e.g. after the installation of Windows on different disk drive)

are two commands:

sudo mount /dev/sdXY /mnt
sudo grub-install --root-directory=/mnt /dev/sdX

Answer 3

1. Boot into Live CD

2. Open Terminal (CTRL+ALT+T)

3. Enter the following commands:

sudo fdisk -l

And find your Ubuntu partition (should be /dev/sda1 if it is the first partition)

sudo mount /dev/sda1 /mnt

sudo mount --bind /sys /mnt/sys

sudo mount --bind /proc /mnt/proc

sudo mount --bind /dev /mnt/dev

sudo chroot /mnt

Now reinstall Grub2

sudo apt-get install --reinstall grub2

Answer 4

I had same problem when i did upgradation. I suggest you to follow the following simple steps: 1) Boot your system with ubuntu live CD or live USB. 2) Open the terminal and run the command sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update 3) Then install boot repair by running the command sudo apt-get install -y boot-repair && boot-repair Launch the boot repair after installing. System->Administration->Boot-Repair menu (Ubuntu 10.04 only) and follow the instruction. It will take 15-20 min to figure out the problem and to fix it. For more help go to the link https://help.ubuntu.com/community/Boot-Repair

Answer 5

You could boot live CD, mount your hard drive, open nautilus as root and copy those files to /boot.