Installing on RAID with Ubiquity [was: Proposal to drop Ubuntu alternate CDs for 12.10]

[Steve Langasek]

Hi Martin,

On Tue, Aug 28, 2012 at 07:38:39AM +0200, Martin Pitt wrote:
> Steve Langasek [2012-08-27 14:50 -0700]:
> >  - RAID is relatively straightforward to turn on post-install.  You install
> >    to one disk, boot to the system, assemble a degraded RAID with the other
> >    disks, copy your data, reboot to the degraded RAID, and finally merge
> >    your install disk into the array.  It's not quick, but it's *possible*.

> I got curious and tried it the other way: I used gparted for creating
> my partitions, installed mdadm in the live system and used it to build
> a /dev/md0, then told Ubiquity to create partitions in that and
> install to it. That part worked fine.

> After Ubiquity was done, there is some unnecessary "fun" though, which
> might still be fixable for Quantal:

>  * It would be nice if Ubiquity could install mdadm for me if it sees
>    that any of its target partitions are on /dev/md*.

>    To do this manually, I tried:

>    * mount /dev/md0p1 /target, chroot /target
>    * apt-get install mdadm; that fails because /etc/resolv.conf is
>      empty, so exit chroot, apt-get download mdadm, copy to
>      /target/tmp, chroot again, dpkg -i
>    * that fails because it cannot access /dev etc, so back out of the
>      chroot, bind-mount /dev/, back into the chroot, dpkg
>      --configure -a, get scared by the warnings about not being able
>      to load MD suppport

>    If ubiquity would install it along with its other setup, these
>    would be avoided.

>  * After that, booting fails because the generated grub configuration
>    hardcodes /dev/md0p1, but initramfs/kernel create it as /dev/md127p1. 
>    It would be nice if grub/Ubiquity used UUIDs for the root partition
>    as usual; in the initramfs /dev/disks/by-uuid/... exists just fine.

> After that, the system boots just fine. I think this approach is still
> faster than post-install setup of RAID.

> Is it desirable/possible to fix these issues? If so, I'm happy to file
> two bugs for these issues.

I'm not convinced that this is an install method we would want to recommend
to users, but it seems like the work to fix these issues would be a
prerequisite for supporting RAID in ubiquity - so yes, please file bugs
about this.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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