I had a CentOS 5.4 x86_64 machine where I imaged the primary partition with the following command so that I could run it in a VM on my local machine for testing.
#dd bs=1024 count=10482412 if/dev/sda of/mnt/storage/sda.img
Then I converted the image on my local machine with the command:
#VBoxManage convertdd sda.img sda.vmdk --format VMDK --variant Standard
I created a new VM and loaded this image as the hard disk. I booted with a Cent OS 5.4 x85_64 installation DVD into rescue mode. I chrooted into the image and reinstalled grub by doing the following:
#mount --bind /proc /mnt/disks/sda1/proc
#mount --bind /dev /mnt/disks/sda1/dev
#mount --bind /sys /mnt/disks/sda1/sys
#chroot /mnt/disks/sda1
#grub-install hd0
Then I rebooted the VM and grub displayed 3 selections. I've tried all 3 of them and I get a kernel panic every time. It starts booting and then I get the following message from each of the 3 choices: "Kernel Panic - not syncing: Attempted to kill init!"
I'm not sure what to do to get it to boot properly...