>>>>> On Mon, 26 Jun 1995 23:47:44 -0400,
	kenn@remus.rutgers.edu (Ken Nakata) said:

> I'm sorry if this is a dumb question, but I keep getting this:
> [~]$ mount -t union -o -b /usr/src/sys $HOME/sys
> union: Operation not supported

> It's the same if root does this.  I have "options UNION" in my
> config file, of course.  My system is current as of June 20th.

I think your $HOME/sys partition is mounted by NFS.
If you'd like to use UNION-fs read-write mounting, you have to use 
UFS (== FFS/MFS/LFS) partition as top layer. 
If top layer is NFS, you cannot mount read-write, but read-only.

Probably you can use "mount -t null -o union" for sys/arch/XXX/conf
and sys/arch/XXX/compile in this situation, instead of "mount -t union".
--
soda@sra.co.jp		Software Research Associates, Inc., Japan
(Noriyuki Soda)		   software tools and technology group