Re: Upgrading a software RAID

[Thomas Fjellstrom <tfjellstrom@shaw.ca>]

On Tue June 2 2009, Bill Davidsen wrote:
> Maxime Boissonneault wrote:
> >>>> 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.
> >>>
> >>> RAID5 should not be missing, my /home was a RAID5.
> >>
> >> Yes, but /home is only mounted after it's accessed the root partition.
> >> It can then read any modules from the root partition, so the raid5
> >> module could still be missing from the initrd.  I suspect it'll have
> >> included it though.
> >
> > I did as you suggested above. I still get the same error message.
> > I have looked and did not find /etc/initramfs/modules. Instead, I
> > found /etc/initramfs-tools/modules. In this file, there were a couple
> > of comment lines explaining how to enable modules.
> > No modules were included.
> > I uncommented the "raid1" and added "raid5" and ran the procedure again.
> >
> > Still getting the same problem.
> >
> > Since the problem seems to be the boot, I will try to do a fresh
> > install, then restore my backup while keeping the /boot from the fresh
> > install.
>
> If this were Fedora I would be using mkinitrd to get the right modules
> in the boot image, however Ubuntu requires another method, which I don't
> know well enough to describe. You are probably on the right tract
> though, getting the modules and mdadm.conf available at boot.

I assume its more or less like debian, so you just add the modules to 
/etc/initramfs-tools/modules and run: update-initramfs -uk `uname -r`

then the modules you added to the modules file will be added to the initramfs 
file, and loaded into the kernel at that stage.


-- 
Thomas Fjellstrom
tfjellstrom@shaw.ca