>> 	Maybe I'm being blind here, or just plain dumb - but I cannot
>> 	seem to get union mounts working on my NetBSD/sun3 [...]

>> 	[this works on i386, EOPNOTSUPP on sun3]
>> 	mkdir /tmp/mount ; mount_union /tmp/mount /usr/share/doc/

> You probably are trying to union mount over a filesystem that does
> not support "whiteout" operations (i.e. old format FFS).

In case anyone cares, I have a user-level daemon (looks like an NFS
server to the kernel) that provides a full-featured unionish filesystem
without needing whiteouts, without erroring on things like chmod of
files that exist only in the back layer, without producing duplicate
names when reading a directory where an entry exists in both
layers...and unfortunately without the performance of a kernel-resident
filesystem.  (Though it is performant enough that I'm using it now for
/usr/src.)  Someday I may import it into the kernel....

I'll be glad to send it to anyone interested.  (I need an excuse to
clean it up so it'll compile on a stock NetBSD system anyway. :-)

					der Mouse

			    mouse@collatz.mcrcim.mcgill.edu