[lxc-users] LXC not starting with already mounted LV as read-only mount

[Claudio Kuenzler]

Hello all,

OS: Ubuntu 14.04.1 LTS
LXC Version: 1.0.6-0ubuntu0.1

Experienced a weird issue when I tried to launch a container which mounts
an additional logical volume (ext4 formatted) through the container's fstab
file:

# cat /var/lib/lxc/mycontainer/fstab
/dev/vglxc/apps mnt/apps ext4 ro 0 0

This LV is already mounted on the physical host:

# mount /dev/vglxc/apps /mnt

Now when I try to launch the container, I get the following error:

# lxc-start -n mycontainer -l trace -o mycontainer.out
lxc-start: Device or resource busy - failed to mount '/dev/vglxc/apps' on
'/usr/lib/x86_64-linux-gnu/lxc/mnt/apps'
lxc-start: failed to setup the mounts for 'mycontainer'
lxc-start: failed to setup the container
lxc-start: invalid sequence number 1. expected 2
lxc-start: failed to spawn 'mycontainer'
lxc-start: The container failed to start.
lxc-start: Additional information can be obtained by setting the --logfile
and --logpriority options.

In the output file the following information is shown:

      lxc-start 1416921918.699 INFO     lxc_conf - Autodev not required.
      lxc-start 1416921918.699 ERROR    lxc_conf - Device or resource busy
- failed to mount '/dev/vglxc/apps' on
'/usr/lib/x86_64-linux-gnu/lxc/mnt/apps'
      lxc-start 1416921918.699 ERROR    lxc_conf - failed to setup the
mounts for 'mycontainer'

When I change the mount option in the container's fstab file from "ro" to
"defaults"  (or basically "rw"), the container starts up:

# cat /var/lib/lxc/mycontainer/fstab
/dev/vglxc/apps mnt/apps ext4 defaults 0 0

# lxc-start -n mycontainer -l trace -o mycontainer.out

      lxc-start 1416921799.912 INFO     lxc_conf - Autodev not required.
      lxc-start 1416921799.912 DEBUG    lxc_conf - mounted
'/dev/vglxc/apps' on '/usr/lib/x86_64-linux-gnu/lxc/mnt/apps', type 'ext4'

If the LV /dev/vglxc/apps is nowhere mounted yet, the container starts up -
with the read only mount option, too.

Is this a (known) bug I ran into?

cheers,
ck
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