repairing a damaged grub with centos

Question

I have a damaged grub in my centos system. to repairing this problem, I use rescue mode and then I execute this follwing comand :

chroot /mnt/sysimage

grub-install /dev/mapper/ddf1OSp3

and then reboot ;

when boot from hard disk, it's sshow error message "file not found"

when I execute the same comand in grub.conf under grub CMD, it s work fine and the file existe !!

how to proceed to resolve this problem

information about system : linux kernel 2.6.

repartition of disk:

$ df

/dev/mapper/ddf1OSp3    /

/dev/mapper/ddf1OSp1    /boot

/dev/sdd1               /data

tmpfs                   /dev/shm

Solution

You don't want to reinstall grub on the LVM. You need to install it on the volume (hard disk, RAID array...) that the motherboard firmware sees. Most commonly:

# grub-install /dev/sda

In some cases, something else other than /dev/sda will make more sense.

Comments

[Ellouze Anis]

according to df command, the root of my system is located in this repartition "/dev/mapper/ddf1OSp3".

[Warren Young]

@EllouzeAnis: That doesn't matter. Grub is executed directly by the motherboard firmware (BIOS or EFI), which doesn't understand LVM. (/dev/mapper/* indicates that you're using LVM.) By putting Grub on the LVM, you've simply hidden it from the mobo FW. Besides, you don't install Grub on the root filesystem anyway. You generally install it on the first physical volume. The mobo FW runs Grub from there, and Grub then goes and finds your OS and boots that.