non-root single user

[Marion Hakanson]

On one of our 4.3bsd machines here we have an init(8) which asks for
the root password before it comes up single user.  Nice enough, but
I would like our backup people to be able to bring it up single user,
not running as root.

As a first hack, I modified this init so it also accepts the password
for the user "backup" and then did a set[gu]id() to that userid.  This
all takes place after init has forked itself to exec the single user
shell, so all I really added was the set[gu]id.  Pretty simple, and it
seems to work OK except that the shell you end up in is running as root.

The question:  Is this approach naive?  I checked the return values on
the set[gu]id calls, and they were fine, but we sure enough end up in
a root shell afterwards.  Is there something in the kernel (or elsewhere)
which is preventing this hack from working?  I looked around a bit, but
didn't see anything obvious (to me :-).

Alternative suggestions would also be appreciated.  Thanks.

-- 
Marion Hakanson         Domain: hakanson at cs.orst.edu
                        UUCP  : {hp-pcd,tektronix}!orstcs!hakanson