After upgrading several systems I'm in charge of from version 5.2 to
version 6.2 I failed to mount disks that were exported from the upgraded
systems. The error message I got on the system trying to mount the disk was
similar to:

   mount: RPC: protocol not supported

(I can't reproduce the error now without disabling nfs on the systems,
which I prefer not to do. Please let me know if you want the exact error).

I searched the net for a solution and it turned out that it has to do with
the fact that portmapper hasn't been initialized properly to deal with nfs
mounts as can be seen by the command 'rcpinfo -p' which didn't list either
nfs or mountd.

I was able to workaround the problem by adding the following line to
/etc/rc.d/rc.local:

cd /etc/rc.d/init.d ; for foo in stop start ; do ./portmap $foo ; ./nfs
$foo ; done

But this should be done by default in runlevel 3.

Please let me know if you need more info.