Today in my busiest hour, after a fool action I lost grub. And as smart as I am, I rebooted the PC, so I got locked out of it.

Well, time to boot with a live CD and reinstall Grub. This is what I’ve done.

sudo mount /dev/hdb3 /mnt

That will mount my root partition in the mnt directory of the Live CD session.

sudo mount /dev/hdb4 /mnt/boot

As I have a different partition for boot, I need to mount it too, inside the /root partition, if you do not have this scenario, you do not need that line.

grub-install --root-directory=/mnt/ /dev/hda

And I got this error:

/dev/hda does not have any corresponding BIOS drive

Well to solve the problem all you need to do is to edit the file, on the mounted partition.

In my case:

sudo vim /mnt/boot/grub/

Then add there:

(hd0) /dev/hda

Also if needed

(hd1) /dev/hdb

In my case those (hd0) and (hd1) were mapped as /sda and /sdb (They are not SATA but Arch Linux works that way, and I was using old Mandriva Live CD).

Once I made the changes, I was able to reinstall grub, and, before restarting I changed the file to its original state.