Recovering from 'grub rescue>' crash

This answer is for others out there that DocSalvager's answer doesn't work for.

1. I followed DocSalvager's use of ls to find the correct hard drive partition. In my case it was (hd0,msdos5).

2. Then I executed the following commands to get back to the normal grub boot loader screen.

   grub rescue>  set boot=(hd0,msdos5)
   grub rescue>  set prefix=(hd0,msdos5)/boot/grub
   grub rescue>  insmod normal  
   grub rescue>  normal  
   

3. After booting into Ubuntu I repaired the grub boot loader with the following commands from the terminal.

   sudo grub-install /dev/sda 
   

Please reference this source for a visual walk through of this process.

Recovering from a grub rescue crash ...

• grub rescue> does not support cd, cp or any other filesystem commands except its own variation of ls which is really a kind of find command.

• So first, had to find the partition with the /boot directory containing the vmlinuz and other boot image files...

  grub rescue>  ls  
  (hd0,4) (hd0,3) (hd0,2) (hd0,1)  
  
  grub rescue>  ls (hd0,4)/boot
  ... some kind of 'not found' message
  
  grub rescue>  ls (hd0,3)/boot
  ... some kind of 'not found' message
  
  grub rescue>  ls (hd0,2)/boot
  ... grub ... initrd.img-2.6.32-33-generic ... vmlinuz-2.6.32-33-generic 
  

  • ls without arguments returns the four partitions on this system.
  • ls (hd0,4)/boot does not find a /boot directory on partition (hd0,4).
  • ls (hd0,3)/boot does not find a /boot directory on partition (hd0,3).
  • ls (hd0,2)/boot finds a /boot directory on partition (hd0,2) and it contains a vmlinuz and other boot image files we want.

• To manually boot from the grub rescue> prompt ...

  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  
  

  • Set root to use the /boot directory on partition (hd0,2).
  • Load grub module linux.
  • Set that module to use the kernel image vmlinuz-2.6.32-33-generic.
  • Set initrd(init RAM disk) to use the image initrd.img-2.6.32-33-generic.
  • Boot Linux.

• This boots to a BusyBox commandline prompt which has all the basic filesystem commands (and then some!).

• Then could move the *.mod files back to the /boot/grub directory ...

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

• Successful Reboot!

See also ...

• stuck at grub rescue on boot, no bios, no live cd, ls returns hd0
• recovering from grub rescue crash (AskUbuntu)
• how to fix error unknown filesystem grub rescue (AskUbuntu)
• A nice Grub 2 ls command reference page
• BusyBox (website)
• BusyBox online emulator