how to recover grub in redhat linux??

how to recover grub          

                                    

Step 1
just insert the RHEL boot disk in your dvd rom
and type ' linux-rescue'  and follow the steps this will take you in rescue mode and you will find the single mode 'recovery' prompt #
Now one message just above to the # displayed and is saying that :your system is mounted under the /mnt/sysimage directry '
Step 2
Type the command

# chroot /mnt/sysimage

and
#grub-install /dev/sda
a message will tell you about successfully installed and no error found.
simple exit reboot and .............
Start

OR

secondly when You failed to install grub using above commands  use this

1. grub

2. grub> root (hd0,0)
Filesystem type is ext2fs, partition type 0×83
3.grub> 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)”… 15 sectors are embedded.
succeeded
Running “install /grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/grub/stage2 /grub/grub
.conf”… succeeded
Done.

4grub> quit

Now you have grub reinstalled into the master boot record of your machine.
Reboot and See