On Sat May 30, 2009 at 02:11:52PM -0400, Maxime Boissonneault wrote:

Ok. This is the configuration I had :
/dev/md1 was a RAID0 composed of /dev/sda2, /dev/sdb2 and /dev/sdc2

I did this :
mdadm --stop /dev/md1
mdadm --zero-superblock /dev/sda2
mdadm --zero-superblock /dev/sdb2
mdadm --zero-superblock /dev/sdc2

and then this :
mdadm --create --verbose /dev/md1 --level=5 --raid-devices=3 /dev/sda2 
/dev/sdb2 /dev/sdc2

I used the rescue mode from an alternate CD (hardy 8.04.2) to format 
/dev/md1 as ext3. Then, I restored the backup and updated the 
/etc/mdadm/mdadm.conf file with the output of mdadm --detail --scan.

Now, GRUB loads (it was on /dev/md0 which is a RAID1 composed of sd*1), and 
it tries to load Ubuntu, but it just won't load.

How far does it get with booting?  It should boot the kernel but fail to
find the root filesystem (if it's an initrd problem anyway).

You said that I would have to edit initrd... what is that and what do I 
have to change in it ?

The initrd is the ramdisk which the kernel boots to first, containing
the various modules and utility programs (like mdadm) needed to access
the main root filesytem.  A quick search suggests that you need to run
'update-initramfs -u' on Ubuntu.  You'll need to boot off the CD and
chroot onto the new array first though - something like:

 - Boot off CD
 - Assemble the RAID arrays
 - Create a mount point for the new array (mkdir /mnt/newroot)
 - Mount the root filesystem (mount /dev/md1 /mnt/newroot)
 - Mount the proc filesystem (mount -o bind /proc /mnt/newroot/proc)
 - Mount the sys filesystem (mount -o bind /sys /mnt/newroot/sys)
 - Mount the dev filesystem (mount -o bind /dev /mnt/newroot/dev)
 - Chroot to the new array (chroot /mnt/newroot /bin/bash)
 - Mount the boot filesystem (mount /boot)
 - Update the initramfs (update-initramfs -u)
 - Unmount the boot filesystem (umount /boot)
 - Exit the chroot (exit)
 - Unmount the dev filesystem (umount /mnt/newroot/dev)
 - Unmount the sys filesystem (umount /mnt/newroot/sys)
 - Unmount the proc filesystem (umount /mnt/newroot/proc)
 - Unmount the root filesystem (umount /mnt/newroot)
 - Reboot

That's just from memory though, so watch out for any warnings/errors.
The other issue you _may_ have is the raid5 module missing from the
initrd - you'd best check that raid5 is listed in
/etc/initramfs/modules.

HTH,
    Robin
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