Recently a good friend of mine managed to uninstall all the kernels from his Ubuntu machine (what can I say – Monday morning and no coffee is a deadly combination). Luckily he had the install CD on hand so we did the following:

1. Boot from the CD (we had Internet connection)
2. Mount the Linux partition and chroot into it

sudo su
cd /media/..
chroot .

3. Reinstall the kernel with aptitude
4. Reboot and go into Grub2 command mode
5. Now do the following (commands need to be adjusted to match your partition – also, tab completion works, so you don’t have to guess)

   insmod part_msdos
   insmod ext2
   set root=(hd0,3)
   linux /boot/vmlinuz-2.6.32.38-generic root=/dev/sda3 ro
   initrd /boot/initrd.img-2.6.38-6-686
   boot

It seems that most of the examples on the ‘net are for Grub 1 and little is out there for Grub 2. I found the following three: How to use Grub2 to boot Linux manually, The Grub 2 Guide, GRUB 2 bootloader – Full tutorial. Also, I didn’t perform steps 4-5 because he just reinstalled Ubuntu (it was a fresh install anyway), but I tried it out separately on my laptop and it works.

HTH