fai 4.0.5: dracut boot ends with kernel panic

[Thomas Lange]

    >>> I'm trying to use dracut in FAI 4.0.5 on a wheezy 64bits server, and the initial boot on nfsroot quickly goes into kernel panic:
    >>> 
    >>> [   11.578824] dracut: Mounted root filesystem a.b.c.d:/srv/fai/wheezy/nfsroot-amd64
    >>> [   11.581213] aufs: module is from the staging directory, the quality is unknown, you have been warned
    >>> [   11.582117] aufs 3.2-20120827
    >>> warning: can't open /etc/fstab: No such file or directory
    >>> [   12.010629] aufs test_add:261:mount[366]: uid/gid/perm /live/image 65534/65534/0755, 0/0/01777
    >>> [   12.015811] type=1702 audit(1358959337.356:2): op=follow_link action=denied pid=371 comm="ls" path="/sysroot/initrd.img" dev="aufs" ino=149
    >>> [   12.015995] type=1702 audit(1358959337.356:2): op=follow_link action=denied pid=371 comm="ls" path="/sysroot/vmlinuz" dev="aufs" ino=165
    >>> /init: 42://lib/dracut/hooks/pre-pivot/50mount-usr.sh: cannot open /sysroot/etc/fstab: No such file
    >>> [   12.260523] dracut: Switching root
    >>> pcbind: rpcbind terminating on signal. Restart with "rpcbind -u"
    >>> switch_root: failed to execute /sbin/init: Not a directory
    >>> [   12.262090] Kernel panic - not syncing: attempting to kill init!

I just ran into the same problem, when I tried an installation from an
newly installed machine running wheezy. The problem is, that nfsv4 is
not configured properly in your setup (and mine) and therefore the
install client (and dracut) cannot mount the nfsroot.

A line in /etc/exports is missing that contains an entry including
fsid=0. I just added this line to my /etc/exports, created an empty
directory /srv/nfs4 and called exportfs -ra.

/srv/nfs4        1.2.3.4/28(rw,sync,fsid=0,crossmnt,no_subtree_check)

That did the trick.

P.S.: 
I did not manage to disable nfsv4 on the install server, because it's
not sufficient to edit RPCMOUNTDOPTS in
/etc/default/nfs-kernel-server. A client still mounts via nfs4.

-- 
regards Thomas