[Bug 774502] Re: Ubuntu 11.04 initrd fails to boot mult-volume BTRFS filesystem

[James Lewis]

Could you add more details regarding what you see as wrong with the grub
or fstab configuration?...  my system seems to stop inside the initrd
environment, so it cannot yet read the fstab from the main system, I
don't understand how the validity of the UUID would change when I added
a second device?

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https://bugs.launchpad.net/bugs/774502

Title:
  Ubuntu 11.04 initrd fails to boot mult-volume BTRFS filesystem

Status in “btrfs-tools” package in Ubuntu:
  New

Bug description:
  After adding second disk to BTRFS volume, Ubuntu 11.04 will no-longer
  boot.  See response from the BTRFS development list.

  On Sat, Apr 30, 2011 at 09:42:39PM +0100, A. James Lewis wrote:
  > 
  > After completing an installation of Ubuntu 11.04 with a separate /boot
  > partition and BTRFS as the main filesystem (Ubuntu creates subvolumes for
  > / and /home).
  > 
  > sda1 being the GPT stuff
  > sda2 being most of the disk as BTRFS
  > sda3 being /boot
  > sda4 being swap
  > 
  > sdb having an identical partition table...
  > 
  > I patched everything up to date, rebooted to make sure that all was ok..
  > and then ran:-
  > 
  > btrfs device add /dev/sdb2 /
  > sync
  > reboot
  > 
  > The system stops in initrd unable to find the root filesystem...
  > 
  > It's my understanding that nothing should change here, am I missing
  > something, I don't see how it can even tell I've added more storage, let
  > alone fail to boot.

     In order to mount a multi-volume btrfs filesystem, the kernel needs
  to know all of the devices that make up the filesystem. It can't do
  that itself, so it needs some userspace assistance. Your system needs
  to run "btrfs dev scan" from the initrd before attempting to mount the
  root filesystem. On Debian, installing btrfs-tools will (I believe)
  set that up.

     To get the system booting again temporarily, you could try adding
  the option "mount=device=/dev/sda2,device=/dev/sdb2" (I think) to the
  kernel command-line parameter in your boot loader. That should give
  enough information to the initrd to be able to find the volumes that
  your btrfs lives on, and get you enough of a system that you can work
  out what's wrong with your initrd.

     Hugo.

  ProblemType: Bug
  DistroRelease: Ubuntu 11.04
  Package: btrfs-tools 0.19+20100601-3ubuntu2
  ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
  Uname: Linux 2.6.38-8-generic x86_64
  Architecture: amd64
  Date: Sat Apr 30 23:34:14 2011
  InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
  ProcEnviron:
   LANGUAGE=en_GB:en
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  SourcePackage: btrfs-tools
  UpgradeStatus: No upgrade log present (probably fresh install)