[Pkg-uml-pkgs] Bug#651307: user-mode-linux: mounting of nfs fails with: bad mount option value specified: vers=4

[Pavel Labath]

Package: user-mode-linux
Version: 2.6.32-1um-4+35squeeze2
Severity: normal

Mounting of a nfs (v3) folder in an uml host fails with the following error:
# mount -v localhost:/srv /mnt
mount: no type was given - I'll assume nfs because of the colon
mount.nfs: timeout set for Wed Dec  7 16:32:14 2011
mount.nfs: trying text-based options 'vers=4,addr=127.0.0.1,clientaddr=127.0.0.1'
NFS: bad mount option value specified: vers=4
mount.nfs: mount(2): Invalid argument
mount.nfs: trying text-based options 'vers=4,addr=127.0.0.1,clientaddr=127.0.0.1'
NFS: bad mount option value specified: vers=4
mount.nfs: mount(2): Invalid argument
mount.nfs: an incorrect mount option was specified

Manually specifying -o vers=3 as the mount parameter works around the issue.
When I manually recompile the kernel to include support for NFSv4 (I added both
nfs server and nfs client, but maybe only client would suffice) the problem
disappers (even though the folder is still exported as NFSv3). My guess is that
the mount.nfs helper expects (because it was built against the "normal" debian
kernel, which supports v4) that the kernel knows what v4 is and when that
assumption fails, it goes berserk.

I recommend includint the support for nfs4 in the uml kernel, to make it behave
more like the default kernel. This will fix the issue, but it still might be a
good idea to notify (nfs) upstream and let them know their that the mount helper
is not very "robust".

-- System Information:
Debian Release: 6.0.2
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.32-5-686 (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages user-mode-linux depends on:
ii  libc6                       2.11.2-10    Embedded GNU C Library: Shared lib
ii  uml-utilities               20070815-1.1 User-mode Linux (utility programs)

user-mode-linux recommends no packages.

Versions of packages user-mode-linux suggests:
pn  rootstrap                     <none>     (no description available)
pn  slirp                         <none>     (no description available)
ii  user-mode-linux-doc           20060501-1 User-mode Linux (Documentation)
pn  vde2                          <none>     (no description available)
pn  x-terminal-emulator           <none>     (no description available)

-- no debconf information