Use UUID for root file systems on /dev/md*

Bug #1043096 reported by Martin Pitt on 2012-08-29
This bug affects 3 people
Affects Status Importance Assigned to Milestone
grub2 (Ubuntu)

Bug Description

As part of the ongoing discussion about dropping alternates [1] I wanted to find out whether it's currently possible at all to install on a RAID with Ubiquity. Turns out it is possible [2], but there are two post-installation steps which are not obvious and should be fixed.

Creating partitions with gparted and building a RAID with mdadm on the live system works well. Ubiquity detects the devices and you can partition /dev/md0 and install on it just fine. The trouble starts because you need to install mdadm into the target system, which is covered in bug 1043094.

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 installed system boots perfectly.


Martin Pitt (pitti) wrote :

Helpful hint from Tom H: "the usual reason for mdadm to rename "/dev/md0p1" "/dev/md127p1" is that the hostname of the system on which the array's first assembled is stored in the md metadata and the array's assembled with a different name on a system with a different hostname. A simple solution would be for the array creation use "--homehost" whether it's automated or manual."

Changed in grub2 (Ubuntu):
importance: Undecided → High
Alexandros (akarypid) wrote :

I just ran into some trouble with my desktop LVM/raid setup after updating my 12.04 installation's udev. I've been searching through launchpad to find if anyone else has the problem and this seems quite related. Are changes made to support LVM install in 12.10 being backported to 12.04? In my first update after 12.10 was release (note: I am still on 12.04) my LVM/raid setup stopped working because of the way initrd works (see bug 1074597)

Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in grub2 (Ubuntu):
status: New → Confirmed
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