[Unionfs] unionfs 2.1 and NFS exports

[Michael MacDonald]

Anyone?  Anyone?  Bueller?  :)

I've gotten the impression from reading through the list archives that
what I'm trying to do should work in theory.  If I'm mistaken, I'd
really appreciate confirmation so that I don't waste time trying to
figure out what's broken.

Do I need to be using the ODF branch in order to get NFS export
capabilities?

I'm also willing to play with a newer kernel, if that is more likely to
work -- I just don't want to go through the trouble only to discover
that it doesn't work either.

Thanks!

Mike

On Thu, 2007-08-09 at 07:49 -0400, Michael MacDonald wrote:
> Hi list.
> 
> Pertinent facts:
> Kernel: Linux lts-build-x86-64-0 2.6.20.3-ubuntu1 #1 SMP Wed Aug 8
> 18:48:49 MDT 2007 x86_64 GNU/Linux
> Unionfs: [  448.574713] Registering unionfs 2.1 (for 2.6.20.14)
> 
> This is a standard Ubuntu Feisty kernel, except that the old unionfs
> (1.3 vintage, I believe) has been ripped out and the 2.1 patch from
> yesterday dropped in.
> 
> ---------------------------------------------------------------------
> Examples:
> 
> NFS server:
> root at lts-build-x86-64-0:~# mount -tunionfs
> -odirs=/mnt/rw/sata1/sles10-x86_64=rw:/mnt/ro/sles10-x86_64=ro
> none /mnt/union/sata1/sles10-x86_64
> 
> root at lts-build-x86-64-0:~# grep union /etc/exports 
> /mnt/union/sata1/sles10-x86_64
> *(rw,no_root_squash,no_subtree_check,fsid=42)
> 
> NFS client:
> root at lts-head:~# mount 10.8.0.124:/mnt/union/sata1/sles10-x86_64 /mnt/
> mount: 10.8.0.124:/mnt/union/sata1/sles10-x86_64 failed, reason given by
> server: Permission denied
> 
> NFS server:
> root at lts-build-x86-64-0:~# grep mountd /var/log/daemon.log
> Aug  9 05:32:12 lts-build-x86-64-0 mountd[4443]: authenticated mount
> request from lts-head.co.cfs:814 for /mnt/union/sata1/sles10-x86_64
> (/mnt/union/sata1/sles10-x86_64)
> 
> root at lts-build-x86-64-0:~# ls -l /mnt/union/sata1/sles10-x86_64/
> total 100
> drwxr-xr-x  2 root   root   4096 2007-08-08 05:39 bin
> drwxr-xr-x  3 root   root   4096 2006-09-21 16:51 boot
> ...
> 
> root at lts-build-x86-64-0:~# touch /mnt/union/sata1/sles10-x86_64/foo
> root at lts-build-x86-64-0:~# ls -l /mnt/rw/sata1/sles10-x86_64/
> total 0
> -rw-r--r-- 1 root root 0 2007-08-09 05:34 foo
> 
> root at lts-build-x86-64-0:~# umount /mnt/union/sata1/sles10-x86_64
> 
> NFS client:
> root at lts-head:~# mount 10.8.0.124:/mnt/union/sata1/sles10-x86_64 /mnt/
> root at lts-head:~# mount -tnfs
> 10.8.0.124:/mnt/union/sata1/sles10-x86_64 on /mnt type nfs
> (rw,addr=10.8.0.124)
> 
> ----------------------------------------------------------------------
> 
> GRR!
> 
> If it's not completely obvious what I'm trying to do, I'll put it
> another way:  I want to create a set of per-client,per-distro,per-arch
> copy-on-write unions to allow each diskless node to have its own
> writable NFS root.  We have a bunch of nodes in a test cluster, and much
> of the testing we do is with ancient linux distros that won't do unionfs
> on the client side (at least, not without MUCH more hacking than I want
> to do).  My brilliant (at the time) idea was to just handle the unionfs
> gunk on the NFS server side.
> 
> What am I missing?  Thanks in advance for any help.
> 
> Mike
> 
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