How is "single-user" done?

[Bruce Walker]

[Articles are packed by weight; contents may settle during shipping]

There have been a number of articles lately, discussing the merits and
problems associated with the various UNIX packages for the IBM-PC.  As I am in
the market for just such a product, I have been following these with great 
interest.  One point that has been raised concerning some of the Unices
(esp. PC-IX) is that they are "single-user".  Now this makes me wonder: how
did the vendor accomplish this restriction?  Is it not true that one could add
more users by simply adding names to /etc/passwd and more ttys with /etc/mknod
and spawn more tty-listeners with lines in /etc/inittab?  Or do they run the 
system in "single-user mode" (ie super user) mode all the time?  That thought
makes me cringe.  I suspect that, in reality, the only restriction on the
number of users is the license itself.  That, however, is like buying a
living-room couch which can physically seat four persons, but which comes with
a "single-user license" which says that any number of people may sit, but only
one at any given time.

Does anyone have any hard info?  Has anyone modified PC-IX to run multi-user?


Bruce Walker     {allegra,ihnp4,linus,decvax}!utzoo!aesat!bmw