Editing Repair GRUB Installation (section)

== Reinstall GRUB ==
If the repair tool can't salvage your configuration, you will need to reinstall GRUB.  This does require a live ISO image of the same distribution as is on the main system drive.

The trick here is that you have to fool the GRUB installer into thinking it is working on the OS image on the system drive, but with the multitude of faux filesystem in a current Linux system, you need to make sure enough of them are available in the main disk image:

 sudo mount /dev/sda1 /mnt
 sudo mount --bind /dev /mnt/dev &&
 sudo mount --bind /dev/pts /mnt/dev/pts &&
 sudo mount --bind /proc /mnt/proc &&
 sudo mount --bind /sys /mnt/sys

Now you can do the installation of the new grub configuration:

 sudo grub-install -root-directory=/mnt/ /dev/sda

If that succeeds, then you need to clean things up:

 sudo umount /mnt/sys &&
 sudo umount /mnt/proc &&
 sudo umount /mnt/dev/pts &&
 sudo umount /mnt/dev &&
 sudo umount /mnt

Of course, substitute the correct device name for your main system drive ...