Bug#762984: Alert! /dev/vg0/usr does not exist

[Javier Barroso <javibarroso@gmail.com>]

Hello Simon, (I'm dropping CCs, I'm not sure if all body is ok with
maintaining such CC list, sorry if somebody have would like to be in
CC)

On Thu, Nov 27, 2014 at 12:51 PM, Simon McVittie <smcv@debian.org> wrote:
> On Wed, 01 Oct 2014 at 22:18:53 +0100, Ben Hutchings wrote:
>> I suspect this is essentially the same bug as #616689 and #678696,
>> except that now it may affect mounting /usr as well as /.
>
> I think this bug report is actually describing more than one bug in more
> than one package that have similar symptoms. There might be things
> that can be fixed in mdadm and lvm2 to fix the initramfs-tools/0.117
> regressions without needing to implement a full event-driven setup in
> initramfs-tools.
>
> ---- RAID (Elimar, Sven) ----
>
> Elimar Riesebieter's "System 2" has a bunch of mdadm (RAID) partitions.
>
> Elimar, what is in your /etc/default/mdadm on "System 2" (and "System 1"
> for that matter)? I predict that the answer includes something like
> "INITRDSTART=/dev/md6".
>
> The problem here seems to be that mdadm tries to determine a minimal
> set of multi-disk partitions need to be assembled by the initramfs
> based on the assumption that the initramfs only needs the root device;
> but initramfs-tools >= 0.117 wants to mount /usr as well, so that
> assumption is no longer true.
>
> So it might be necessary to modify mdadm so that, if /usr is a separate
> filesystem on (a LVM VG on) a MD array, it will try to prepare that too.
>
> ---- LVM (Elimar's "System 1", Sven, Torsten, IOhannes, Javier) ----
>
> In the LVM case, debian/initramfs-tools/lvm2/scripts/local-top
> does this:
>
>     activate_vg "$ROOT"
>     activate_vg "$resume"
>
> Note the lack of handling for /usr here.
>
> Further, activate_vg uses "lvm lvchange" to activate only the LV
> necessary for the root filesystem; if /usr is on a separate VG,
> it's not going to work.
>
> This on its own would be enough to make Sven Hartge's system fail:
> /usr needs a LVM partition activated that / does not. Similarly,
> I think Elimar's "System 1" is going to activate vg0/root but not
> vg0/usr.
>
> We don't have enough information in this bug report to know what
> layout Torsten, IOhannes, Javier used on their systems, but we can
> guess from the fact that "vgchange -a y" is a successful workaround...
> I predict that these are LVM over either a single RAID array, or
> real partitions.

My partition layout is:

javi@Doraemon:~$ lsblk
NAME              MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda                 8:0    0 238,5G  0 disk
├─sda1              8:1    0   243M  0 part /boot
├─sda2              8:2    0     1K  0 part
└─sda5              8:5    0 238,2G  0 part
  ├─doraemon-root 254:0    0  13,4G  0 lvm  /
  ├─doraemon-swap 254:1    0   3,7G  0 lvm  [SWAP]
  ├─doraemon-var  254:2    0  11,3G  0 lvm  /var
  ├─doraemon-tmp  254:3    0   4,7G  0 lvm  /tmp
  ├─doraemon-opt  254:4    0   9,3G  0 lvm  /opt
  └─doraemon-home 254:5    0  65,2G  0 lvm  /home

$ sudo lshw -c disk
  *-disk
       description: ATA Disk
       product: C400-MTFDDAK256M
       physical id: 0.0.0
       bus info: scsi@0:0.0.0
       logical name: /dev/sda
       version: 0G09
       serial: 0000000012440352D97A
       size: 238GiB (256GB)
       capabilities: partitioned partitioned:dos
       configuration: ansiversion=5 logicalsectorsize=512
sectorsize=512 signature=573692f2

Before this bug, i have too /usr ( doraemon-usr logical volume)
splited. I moved /usr into / after Ben suggested at a comment in this
bug.

The same happened in another computer which had the same partition layout

Thank you very much