http://sn.1w6.org/file/mk-20140920T211032-269yvs7.html
Enough poking around for today - my brain absorbed quite a lot of information, but I STILL don't know how the #NAS restricts login to root and admin only. It may actually be controlled by a specially-compiled sshd (?) - I can't think of anything else. :( I'll have a small bite and relax a bit before retiring.