[CentOS] CentOS 6.2 on partitionable mdadm RAID1 (md_d0) - kernel panic with either disk not present

Mon Oct 15 10:32:52 UTC 2012
Arun Khan <knura9 at gmail.com>

__ SOLVED __

On Sat, Jun 23, 2012 at 10:14 AM, Arun Khan <knura9 at gmail.com> wrote:
> I have not had a thorough look at the dracut script though.

I also posted this problem on the mdadm mailing list but could not get
the problem resolved.

So did some searching on the suspect candidate 'dracut'

After some more searching I found these two bugs reports:
CentOS 6.2 <http://bugs.centos.org/view.php?id=5400>
CentOS 6.3 <http://bugs.centos.org/view.php?id=5970>

Using "System Rescue CD" and mounting the disk image files, I appended
'rdshell' to the kernel line in grub.conf.

With 'rdshell' one can at least do the following to get the system operational.

Booted the system with a disk failure

At the rdshell prompt:

# mdadm --run /dev/md_d0
(replace device name with your device name)

# cat /proc/mdstat
(make sure your raid device is active with one member failure)

(exit the rdshell)

The system will boot with md_d0 in degraded mode.

Login in to the system.

# yum update dracut
(dependency dracut-kernel is pulled in)

As of this writing it is dracut-004-284.el6_3.1.noarch

# cd /boot
# dracut  <initramfs file name>  <kernel version>

Update grub and reboot.

System boots with when either disk has failed.

-- Arun Khan