Re: unable to mount using overlayfs.v22 on kernel 3.15.5

Woody Suwalski
2014-07-24T12:12:59Z

Klaus A. Kreil wrote:
> Hello list,
> I have just found out about this mailing list which obviously also
> takes care of overlayfs.
>
> I have been a happy user of overlayfs for quiet some time using it to
> propagate a shared r/o LVM ext4 lowerdir rootfs with a small r/w ext4
> upperdir for a number of XEN domU guests. I started with overlayfs on
> kernel version 3.11.7 (all on gentoo-hardened). Recently I have
> switched from 3.13.10 (using overlayfs.v21) to 3.15.5 with overlayfs.v22.
>
> overlayfs.v22 seems to have changed insofar as there's a new parameter
> workdir=/dir with dir required to be an empty directory on the same
> filesystem as upperdir. So I have changed my initramfs to include that
> parameter and have also created my /dir directory (named /.work, owned
> by root:root and 0755 mode) on all my individual upperdir filesystems
> for all of my XEN domUs.
>
> Now when I start the new kernel 3.15.5 with the modified init script
> from the newly created initramfs, I am ending up in a rescue shell.
> Both the upper and lower filesystem are (as expected) mounted
> appropriately to /mnt/root_ro and /mnt/root_rw amd /mnt/root exists.
> Howeverm, trying to combine those two filesystems on /mnt/root (as
> before and regardless of whether used with or without the workdir=
> parameter) fails with an error message as follows:
>
> # mount -t overlayfs overlayfs -o
> lowerdir=/mnt/root_ro,upperdir=/mnt/root_rw,workdir=/.work /mnt/root
> mount: mounting overlayfs on /mnt/root failed: Invalid argument
>
> The error message stays the same regardless of where on the command
> line the overlayfs "device" parameter appears. I can't see what's
> wrong with the command line given that - with the exception of the
> workdir=/.work part - the command has not changed from 3.13.10
> (overlayfs.v21), therefore currently leaving me at loss.
>
> I would very much appreciate any help and support in tracking down
> this unexpected issue.
>
> Regards Atom2
Klaus, I have run into similar problems...
What works for me:
Once you mount the upperdir /mnt/root_rw, create /mnt/root_rw/root and
/mnt/root_rw/workdir and use these for overlayfs mountpoints.

Woody