[CentOS] Replacing failed software RAID drive
Hugh E Cruickshank
hugh at forsoft.com
Wed Oct 10 21:46:55 UTC 2007
From: Les Mikesell
> Hugh E Cruickshank wrote:
> > From: Les Mikesell Sent: October 7, 2007 18:53
> >> 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.
Sorry to be obtuse here but I just want to make very sure of what I am
doing before I do it. Will the "setup" command only write the MBR?
>From my reading the GNU GRUB manual I got the distinct impression that
the "setup" command will also write/rewrite the /boot partition (which
I would like to avoid). The documentation for the setup command states:
Set up the installation of GRUB automatically. This command uses
the more flexible command install (see Section 13.3.18 [install],
page 44) in the backend and installs Chapter 13: The list of
available commands 49 GRUB into the device install device. If
image device is specified, then find the GRUB images (see Chapter
10 [Images], page 29) in the device image device, otherwise use the
current root device, which can be set by the command root. If
install device is a hard disk, then embed a Stage 1.5 in the disk
The option --prefix specifies the directory under which GRUB
images are put. If it is not specified, GRUB automatically
searches them in /boot/grub and /grub.
The options --force-lba and --stage2 are just passed to install
if specified. See Section 13.3.18 [install], page 44, for more
The second paragraph tends to imply that /boot/grub will be written
to by default and I do not think that this is what I want to happen.
Thanks again for everyone's input (especially Les). It is greatly
Hugh E Cruickshank, Forward Software, www.forward-software.com
More information about the CentOS