(Re)installing GRUB to the MBR

NOTE: This post has moved to https://blog.gibson.sh/2013/12/31/reinstalling-grub-to-the-mbr/
The original article is kept here for now, but is not maintained in any way.

This is just a very short roundup of the relevant commands needed to reinstall grub, e.g. when migrating a Linux installation to a new hard drive.

• boot live Linux system (from CD/DVD or USB key, I use grml, any other live Linux should do)
• mount root-fs of your installation (e.g. /dev/sda2) to /mnt/
• if they’re in separate partitions, mount the /boot/, /usr/, … partitions of your installation to /mnt/boot, /mnt/usr/, …
• mount --bind /dev/ and /sys/ to /mnt/dev and /mnt/sys (maybe also /proc for older versions of grub?), grub will need those
• chroot /mnt
• execute grub-install $device (e.g. /dev/sda) to install grub to the MBR of $device
• update-grub to upgrade the grub menu entries
• If names of partitions changed, don’t forget to adjust /etc/fstab
• configure your BIOS to boot from that harddisk
• reboot, remove live linux you should be greeted by a fresh grub that lets you boot your Linux, BSD, Windows, .. installations