If you're finding that the NFS mount of a file-system is hanging, here's one reason we found. On servers with multiple interfaces (e.g. a server that is also router which is a really bad idea in the real world but needed in our lab.) it's important that you refer to the server by its proper interface. With topsecret, it has a 139A, 139B, and 137 subnet address. The machines on that department network must mount filesystems like "topsecret.cs.unc.edu:/usr". Machines that communicate with topsecret via its 139A interface should mount those filesystems as "topsecret139.cs.unc.edu". Otherwise, the nfs client will receive replies from topsecret139 when it is expecting replies from topsecret137 and ignore them, leaving the process hanging.