Below steps will help to rebuild / reinstall the corrupted or unknowingly deleted Grub Boot loader using the rescue mode in Redhat / Centos.
- Boot the system from Redhat / Centos Installation Disk/DVD or Flash Drive
- Type the ‘linux rescue’ command at the installation prompt to enter into the rescue environment.
- Type the command ‘chroot /mnt/sysimage’ to mount the root partition.
- Type the command ‘/sbin/grub-install /dev/sda’
to reinstall the GRUB BOOT LOADER here boot partition is there in 'sda'.
- Review the /boot/grub/grub.conf.
- Then Reboot the server