jails; sharing parts of file system; mounting pieces of file system in other positions, etc.

[Chad Leigh -- Shire.Net LLC]

On linux you can do a

% mount -bind olddir newdir

to remount a piece of the FS somewhere else.  The NullFS on FBSD seems 
to allow similar things.  However, as much as I could find on NullFS in 
Google seems to indicate that it is pretty much broken and shouldn't be 
used.

What I want to do is run several jails that would share the "read only" 
pieces of a system like / /bin /sbin /usr/bin /usr/sbin and stuff like 
that.  Each jail would have their own /etc and other places that would 
need to be different and writable.  This way I only have to update the 
system once when I upgrade and not do all my various jails one at a 
time. Of course, some things would need to be done for each jail (etc 
updates etc) but this would minimize it...

Is this a possible thing to do under FBSD?  How are others doing it?

Thanks for your input

Chad