Just a note to other NFS server users - There's a kernel bug that can cause unmounting an NFS share to segfault (and not actually unmount anything.)
I had in in the kernel 3.10 version, perhaps even before that as I don't update the kernel on my mythtv backend server that often. It hangs the shutdown process with an oops and it will require physical manual intervention to shut the machine down. If you upgrade to 3.11.5 or greater the problem goes away. I've been banging my head against the wall with this for over a week and *finally* found a resolution after going through a lot of NFS searches via Google. Dan
