Grub Recovery on CentOS 5 with RAID
I recently replaced the RAID 1 drives in my CentOS 5 box and had to reinstall the grub MBR. As the drives are a couple of TB each, I thought I’d try GPT instead of the old MBR partitioning, since soon all drives will exceed MBR’s 2TB limit. Luckily GPT is baked into RH/CentOS kernels (unlike many others).
Restoring the MBR was trickier than I expected and I made a couple of mistakes along the way – wish I had found the following description sooner:
In a nutshell run grub interactively and do the following:
# grub grub> root (hd0,0) root (hd0,0) Filesystem type is ext2fs, partition type 0xfd grub> setup (hd0) setup (hd0) Checking if "/boot/grub/stage1" exists... no Checking if "/grub/stage1" exists... yes Checking if "/grub/stage2" exists... yes Checking if "/grub/e2fs_stage1_5" exists... yes Running "embed /grub/e2fs_stage1_5 (hd0)"... 16 sectors are embedded. succeeded Running "install /grub/stage1 (hd0) (hd0)1+16 p (hd0,0)/grub/stage2 /grub/grub.conf"... succeeded Done. grub> quit # reboot