Reinstalling Grub

When Microsoft Windows is reinstalled on a multiboot computer, it will overwrite the MBR wiping out the existing Grub install. To reinstall Grub do the following:

  1. Boot to the most recent ArchLinux install CD and select the correct architecture (on dual ISOs).
  2. Mount your existing ArchLinux install on /mnt: mount /dev/sda# /mnt
  3. If necessary, mount your boot partition: mount /dev/sda# /mnt/boot
  4. Reinstall grub: grub-install –root-directory=/mnt /dev/sda

Older instructions

To install the grub bootloader from a LiveCD:

  • Mount the root filesystem
    • mkdir /mnt/root
    • mount -t ext2 /dev/?da? /mnt/root
  • Populate the dev and proc filesystems
    • mount -o bind /dev /mnt/root/dev
    • mount -t proc none /mnt/root/proc
  • Change to the mounted root filesystem
    • chroot /mnt/root
  • Install grub in MBR
    • grub
    • find /boot/grub/stage1
    • root (hd0,0) # Use the info from the above find command
    • setup (hd0) # Use the info from the above find command
    • quit
  • Reboot!

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