Re: Upgrading a software RAID

[Thomas Fjellstrom <tfjellstrom@shaw.ca>]

On Tue June 2 2009, Bill Davidsen wrote:
> Thomas Fjellstrom wrote:
> > 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.
>
> Is there some explicit action needed to get the mdadm.conf file added to
> the image?

I'm not entirely sure. But automatic arrays will build fine. set the partition 
types to "fd" and make sure the array saved the metadata to the disks, and the 
kernel should bring the arrays up automatically.

-- 
Thomas Fjellstrom
tfjellstrom@shaw.ca