[lxc-users] "overlayfs: missing upperdir or lowerdir or workdir." Can it be ignored?

[KATOH Yasufumi]

Hi,

>>> On Wed, 24 Jun 2015 13:39:43 +0200
    in message   "[lxc-users] "overlayfs: missing upperdir or lowerdir or workdir."	Can it be ignored?"
                  Ingvar  Bogdahn-san wrote:

> Hi again,

> I'm having another problem with overlayfs and unprivileged lxc containers. When cloning with
> overlayfs, I get
> "overlayfs: missing upperdir or lowerdir or workdir"
> but cloning appears to succeed.

> I was using ubuntu 14.04 as host OS. Since overlayfs got kernel support in 3.19 kernels, I updated
> the kernel to 3.19 using the packages linux-headers-generic-lts-vivid  &
> linux-image-generic-lts-vivid. I then recreated a new mother container, without adding a user to
> it. I cloned it again using lxc-clone -o mother2 -n overlay2 -B overlayfs -s  and got again the
> error:

> [130.841743] overlayfs: missing upperdir or lowerdir or workdir
> Created container XY as snapshot of X

> Although it starts the clone despite that error, I still keep getting "failed to whiteout" and
> "Operation not permitted" when doing lengthy installations, see
> previous thread.

Is the container on ext4? At the 3.19 kernel, the upperdir and workdir
of overlayfs must be on ext4, because only ext4 supports the
"whiteout" function. 

> Here:
> https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/1409425
> they report the same problem with  lxc-start-ephemeral, and claim it to be fixed with current
> version. After upgrading to lxc version to 1.1 using the ppa:ubuntu-lxc/daily, I still get
> "overlayfs: missing upperdir or lowerdir or workdir"

> However, fortunately after the update to lxc 1.1, non-trivial installations succeed !! I tried by
> installing wordpress and > 150MB of dependencies, which repeatedly failed before.

> So, my remaining question is: can the error message be simply ignored?
> "overlayfs: missing upperdir or lowerdir or workdir."

If you succeed clone and start, you can ignore it.

The reason is that LXC supports various versions of overlayfs.

Old overlayfs (that is before merging kernel) is mounted without
"workdir" option. But current overlayfs need it.

At the beginning, LXC tries mounting overlayfs without workdir. If it
failed, LXC mounts it with workdir option. So when the mount fails
without workdir, the failed log is output.

--
KATOH Yasufumi