Machine is booted into Grub Menu
I am using rescue linux

by doing fdisk -l

it shows
Disk /dev/sda : bla bla bla
Device Boot
/dev/sda1 *

so i install grub using this command in shell

grub-install /dev/sda1

it shows

installation finished. No error reported
This content of the device map /boot/grub/device.map


After re-boot it again shows grub menu

Since the information you provide shows CentOS as the only system installed, you should install to /dev/sda which would be the master boot record. The method you used installs to the partition so you would need some other boot code from some other bootloader in the master boot record in order to boot CentOS. I believe 6.0 still used Grub Legacy. Do you have a separate boot partition? The info you posted is very limited. If you have the CentOS installation Live CD or some other Live CD, go to the site below and download and run the bootinfoscript. It will output a results.txt file which you can post here and you should get some help with that. Read the instructions in the link in the Description box on the page.

http://sourceforge.net/projects/bootinfoscript/

1 members found this post helpful.

Probably this should help http://www.linuxquestions.org/questi...6/#post5078530

I will run the script and will show results here soon,

For now I have booted from centos live cd
i don't find any thing under my boot /
i have installed grub using grub-install on rescue Linux yet no files appear on boot /
is it save to copy files of "boot" folder from other computer as it has same OS n configuration

Did you mount the /boot partition for the installed CentOS? Actually, you haven't indicated whether you have a separate boot partition or if the boot files are in the boot directory on the / (root filesystem) partition. You need to mount that partition from the Live CD to see/access files there. Did you do that?

Maybe, if the other OS is also CentOS 6.0. Better to post the bootinfoscript output to get a more definitive answer.

I have copied the files to /boot and re install grub and edit grub.conf...then yum update from rescue mode, it works

I still don't know the reason why the machine got crashed and there was nothing Under /boot.

System was running fine..nothing was updated or configured , it just got crashed.

Did your problem got solved?

If not give the output of 'fdisk -l', 'df', 'mount'.

Specify which partition your /boot folder mounts on. Contents of /boot folder.

Specify what version your grub is? Legacy grub have version like 0.97. And newer grub2 has version 1.99 or 2.0.

Yes problem is solved , but i want to know why this problem occurred, to prevent this happening in future.

There was no sudden power-outage nor updates nor hardware config , it just got crashed.

Do you use mechanical HDD with platters and not SSD's?

If so, sometimes some sectors get mapped to others. So a temporary failure. It may indicate a HDD failure. You may run a test of hard disk health either by vendor provided utility or using smartctl tool.

It's a RAID , the health of logical drive is ok.