The dreaded scrolling GRUB GRUB GRUB on startup

Rebooting a server is always stressful, particularly when you don’t have immediate physical access to it. Of course, when the server inevitably doesn’t come back up you need to either get directly on the local console or connect in via KVMoIP and one of the worst things you can see is “GRUB GRUB GRUB” scrolling past endlessly.

This is a sign that stage 1 of the GRUB bootloader which is stored in the Master Boot Record (MBR) has somehow become corrupted and do GRUB can’t start. There is no way to even get into the GRUB command line and boot the system manually or even troubleshoot further as the problem is with stage 1 and not stage 2.

As I ran into this on a CentOS machine, I used a netinstall CD with the virtual media feature on an IP KVM attached to the server to boot into rescue mode and chroot into the operating system installed on the drive in question. I could then identify the /boot hard drive number and partition from /boot/grub/menu.lst ready to re-install GRUB and point it at the stage 2 files.

Simply run /sbin/grub to get to a version of the GRUB command prompt and then (assuming /boot/grub/menu.lst references root {hd0,0) for each of the menu options) just run:

root (hd0,0)
setup (hd0)

You should see a series of messages about looking for stage 1.5 and 2 files and then that it has successfully embedded. Congratulations, GRUB has now been re-installed and simply rebooting your machine should take you straight into your operating system as normal.