Server hang at GRUB during boot - SOLVED

If a RHEL server hangs on boot with nothing more than the word GRUB in the upper left hand corner of the screen, this means that GRUB is unable to read its configuration file. If you actually get a GRUB menu, but the server does not boot then you have different and potentially more complex issue.

The most common reason for GRUB being unable to read its configuration is caused by a discrepancy between how the BIOS enumerated the hard drives and what GRUB expects to be its boot disk.

To correct this issue, boot the server in rescue mode.

Once booted into rescue mode and your root disk filesystems have been mounted. Check the /boot/grub/device.map file to ensure it has correctly identified the boot disk. hd0 should point to the disk that contains /boot. On an HP Proliant system you should see the following line:

(hd0) /dev/cciss/c0d0

If it does not, correct the file and then update GRUB by issuing the following command:

/sbin/grub --batch --device-map=/boot/grub/device.map --config-file=/boot/grub/grub.conf --no-floppy

And then from the GRUB prompt enter the following commands:

grub> root (hd0,0)
grub> setup (hd0)
grub> quit

You can now eject the ISO and reboot the server normally.