Fixing a broken GRUB

When upgrading my Mac OS X to Snow Leopard, OS X took the liberty of wiping out both my refit boot loader and may (chain) loader GRUB on the Linux partition. When booting Linux after the refit screen, I got a "Unknown file system" error.

The remedy was to boot with a Linux live CD (I used systemrescuecd), chroot into the Linux partition and run dpkg-reconfigure on the GRUB package:

First, I found the name of my Linux partition by running:

# fdisk -l /dev/sda

I found it to be/dev/sda4 and could proceed with the command line magic:

# mkdir /mnt/debian
# mount /dev/sda4 /mnt/debian
# mount -o bind /dev /mnt/debian/dev
# mount -o bind /sys /mnt/debian/sys
# mount -o bind /proc /mnt/debian/proc
# chroot /mnt/debian
# dpkg-reconfigure grub-pc

The crux was to rundpkg-reconfigure and select the Linux partition as the destination for GRUB. Funnily enough, it didn't suffice to just runupdate-grub as most people on the net speak of.

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