First try "umount -f /mounted/path/to/umount" - a lot of linuxes and unixes support this now. If you're on a linux system, you can try "umount -l /mounted/path/to/umount". If you get an error about the filesystem being busy, you -may- be able to figure out why the filesystem is busy in a variety of ways: 1) lsof - but may just hang 2) fuser - but may also just hang 3) ps auxwwe | grep /mounted/path/to/umount - but likely won't show all dependencies 4) Take some guesses - what would you Expect to be using that NFS mount? This one's cute, something I thought up :). If you have an NFS server down that's causing the NFS timeout, and it isn't practical to bring the server back up just to do a umount, then you might try creating a virtual interface that has the same IP address as the machine that's down. Be careful though - I once saw a system's outgoing networking get messed up by such a virtual interface, so you may need to remove the virtual interface ASAP after doing your umount.