In some email I received from der Mouse, they wrote:
[...]
> > What about a nullfs mount of /var/etc over /etc ?
> 
> A nullfs union mount, presumably?  That would help a good deal; indeed,
> that would fix essentially all the problems - once you get /var
> mounted.  I'm still thinking (and talking with one or two people
> privately) about various ways to deal with that problem.  Thanks for
> mentioning that.  I think it shouldn't be necessary, but it's an
> excellent way to detect things that write to /etc - run like that for a
> while, shut down, and see what's appeared in /var/etc.

No, not a union mount.  Last time I tried to union mount ro under rw, it
didn't work for the rw bit.

darren