From: utzoo!decvax!cca!Michael.Young.CMU-CS-A@SRI-UNIX@sri-unix
Newsgroups: net.unix-wizards
Title: Re: Why can't I mount or unmount /usr?
Article-I.D.: sri-unix.4839
Posted: Wed Dec 15 03:07:13 1982
Received: Fri Dec 17 06:34:44 1982

From: Michael Wayne Young <Michael.Young.CMU-CS-A@SRI-UNIX>
Date:  9 December 1982 1408-EST (Thursday)
Often mount/unmount is impossible because some process's current
directory is on that filesystem or some file is open there.  I know
of at least one kernel that "revokes" access to files on a structure
if you try to dismount it, but I don't think it tries to get rid
of processes whose current directory is on it (as that's harder
to decide what to do).  You might want to see if some process
that's always running that is stopping you up.

Does your flavour of Unix allow mounts on top of already mounted
systems?  [I'm unfamiliar with the USG-related ones.]  That might
be a no-no entirely.  Otherwise, I can't tell why you wouldn't
be able to handle mounting on /usr/foo.

			Michael