On Sunday 13 March 2011 3:16 pm, Urs Beyerle wrote:
> On 03/13/2011 07:46 PM, Tom H wrote:
> > On Sun, Mar 13, 2011 at 1:33 PM, Urs Beyerle<[log in to unmask]>  
wrote:
> >>> 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.
> >
> > Usually md devices are renamed/renumbered when "/etc/mdadm.conf" has
> > "HOMEHOST<system>" set and the metadata in the superblock has a
> > different homehost value.
>
> The file /etc/mdadm.conf does not exist on the LiveCD. Therefore the md
> devices should not be renamed...? Bluejay, do you see /etc/mdadm.conf, if
> you boot your system with the LiveCD?

I had a similar problem with disks when I lost a system disk and needed to 
rebuild the file system.   Thank god I had a hard copy of print out of "df" 
before it crashed.
This is crude but effective.  I used the install disks - got to the area that 
allowed me to set up and format hard disks.   I named them correctly, and 
organized the data as on hard copy.   The data is still there but the install 
program plays dumb but will allow you to rename everything - set do not 
format.  Continue and when it gets to asking for application - bail out.  
(reboot) and you are there.  Now you have to work on /etc/fstab to make all 
drives physical mounts.  (get rid of logical drive names).   Once this is 
done you should be able to reboot and recover you old data.  You will notice 
that you have a new fstab.
After you have everyting saved to a back up.   Then you can replace disks / 
rename them and use the same scheme to restore you system to use LVM.
A hard way around the apple tree but sometimes it's desperate measures by 
desperate men.   Its crude / rude but effective.

A very usefull utility would be a partial install disk that allows you to do 
disk management and quit the install.

Larry Linder