How to re-install bootstrap code(GRUB)

If you repaired your system from backup tape by dump or tar, you need to repair the bootstrap area.

Re-install bootstrap code (GRUB)

Please do the following steps.

Step 1: Boot from CentOS installation disc (for example, CD #1 or DVD).

Step 2: Type "linux rescue" at the "boot:" prompt.

Step 3: Mount all filesystems in read-write mode.

Step 4: Change root to real root ('/') on your hard disk.

# chroot /mnt/sysimage

Step 5: Re-install bootstrap code (GRUB).

# grub-install /dev/sda

If you re-install GRUB to PBR of Partition #2 on SCSI disk or SATA disk (/dev/sda2).

# grub-install /dev/sda2

# grub-install /dev/hda

# grub-install /dev/cciss/c0d0