> As part of upgrade planning for my main workstation at home (an
> updated SL 5.2 system), I booted from the live CD just to see if all
> the major devices worked. Everything worked :). Unfortunately, that
> act rendered my existing system unbootable.
>
> When I booted from the live CD it found and started my md RAID1
> partitions, including my system root partition. Nice, I had all my
> data there to play with. I noticed that where I had previously used
> /dev/md0, /dev/md1, etc..., the live CD system had created them as
> /dev/md122, /dev/md123, and so on, and not in the original order. I
> didn't think much of this, figuring my regular system would start them
> back in the original configuration, but apparently some metadata
> somewhere got changed by the live CD system and now the original
> system would not get past switching to the root file system with a 'no
> such device' error. I could see, just before going off the screen,
> where it had started my root partition as /dev/md125 rather than
> /dev/md0.
>
> I tried a couple of things to recover from this: I tried stopping and
> reassembling the RAID sets with the desired device names from the live
> CD system, and repackaging my initrd with device files for the
> /dev/md12* devices, but no luck. At that point I decided that, since I
> had already done my backups and was planning on eventually going to
> SL6, that I'd just push forward with a fresh install of SL6. It took a
> few hours that I hadn't planned on to get everything back up to speed,
> and I have one issue yet to work and a couple of minor things to
> configure.
>
> I have another retired box with the same RAID setup and it too, got
> hosed by the live CD. I'm going to play with this box to see if I can
> find a way to recover from this.
>
> Beware.

Thanks for letting us know!

I would be very interesting in a recovery procedure.

I guess that it should be possible to re-assemble the raid device. So in case /dev/md0 was renamed to /dev/125 and was setup with /dev/sda1 /dev/sdb1, you may 
get /dev/md0 back, if you do

mdadm --stop /dev/125
mdadm --assemble /dev/md0 /dev/sda1 /dev/sdb1

Are your raid partition of the type 0xfd (Linux RAID autodetect) or 0x83 (Linux)?

If this is a general problem with the LiveCD and software raids, I would like to fix it on the LiveCD.

I have to admit that I'm not an expert in software raid. If somebody knows how to disable auto-detection of software raids at boot up, please let me know.

Cheers,

     Urs