[CentOS] unable to recover software raid1 install

[S.Tindall]

On Tue, 2015-03-17 at 23:28 +0100, johan.vermeulen7 at telenet.be wrote:
> 
> on a Centos5 system installed with software raid I'm getting: 
> 
> raid1: raid set md127 active with 2 out of 2 mirrors 
> 
> md:.... autorun DONE 
> 
> md: Autodetecting RAID arrays 
> 
> md: autorun..... 
> 
> md : autorun DONE
> 
> trying to resume form /dev/md1

Hi Johan,

Your system is assembling md127, but is apparently expecting md1.

I suspect that you examined the raid1 from a previously working EL5
system using a more-recent-than-EL5 LiveDVD, which assembled the raid1
as md127 and wrote super-minor 127 to the raid1 (assuming ver. 0.90
metadata). When started under EL5, it then assembled as md127, not md1,
hence the problem.

If that is what happened, then boot the system with the same LiveDVD,
stop the raid and then assemble it as md1 while updating the
super-minor. (You might want to mount the installation and look at fstab
and grub.conf while running the LiveDVD to verify that it is looking for
md1).

For example (assuming md1 contained partitions sda1 and sdb1):

- (Boot using the LiveDVD)

- (Unmount anything from md127 > # df -h)

- (Inactivate any VGs/LVs > # vgchange -an <VG> or lvchange -an <LV>)

# mdadm -S /dev/md127

# mdadm -A /dev/md1 -U super-minor /dev/sd[ab]1

Then shut down the LiveDVD and attempt to boot the system under EL5.

Steve

PS I don't watch EL5 boot very often/recently, so I might have misses
something relevant in your post.