[CentOS] Replacing failed software RAID drive

Les Mikesell lesmikesell at gmail.com
Wed Oct 10 03:33:03 UTC 2007

Hugh E Cruickshank wrote:
> From: Les Mikesell Sent: October 7, 2007 18:53
>> OK, you just have to replace the drive, fdisk matching partitions on it 
>> ("fdisk -l /dev/sde" will show the sizes you need), then use
>> mdadm --add /dev/md? /dev/sda?
>> for each one to add the missing partition back.
> I have been able to review all this and it looks very straight forward.
>> Then reinstall grub on the drive.
> Now I have some questions:
> 1. Since the /boot partition was mirrored and will be restored on the
>    new sda drive I do not really want to do a full grub install. From
>    what I have read that will overwrite existing /boot/grub/grub.conf
>    file. So I just want to write the MBR on the drive. How to I do
>    that (the docs I have found were rather unclear on that aspect)?
> 2. Can a install grub on the replaced boot drive with the system still
>    running?

Yes, after the /boot partition re-sync has completed, execute grub and:

root (hd0,0)
setup (hd0)

If you aren't able to keep the system running while doing the swap, you 
can also do this from the rescue mode boot, but you should have the 
contents on the /boot partition first.

   Les Mikesell
    lesmikesell at gmail.com

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