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

[Serge Hallyn]

Quoting Claudio Kuenzler (ck at claudiokuenzler.com):
> 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?

I think it is.  Can you please try with this patch:

https://lists.linuxcontainers.org/pipermail/lxc-devel/2014-November/010876.html

applied?