> From: VaX#n8 <vax@ccwf.cc.utexas.edu>
> Subject: user-land file systems
> To: tech-kern@netbsd.org
> Date: Sat, 17 Jun 1995 02:51:11 -0500 (CDT)
> 
> ...
> I'm aware of the cfs (crypted file sys) design that uses NFS on a loopback
> interface, but I think this is hideous, especially on a machine that wouldn't
> otherwise be running NFS.  And NFS has a history of being way insecure.
> 
NFS also does not export a complete VFS interface.  Since it is stateless
I think it lacks things like open and close calls.

A couple of grad students at UCB did a prototype user-level filesystem 
interface as an O.S. project.  I got the code from them so that a couple of
our grad students could use it to build a (surprise!) compressing file
system (they never used it however, nor did they finish the project).
I'll dig up their names so you can contact them if you are interested.

As someone else mentioned, there are a number of "trust" problems that have
to be addressed if you are going to let user's provide file system servers.