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

[Woody Suwalski]

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
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