Is UNIX(TM) Multi-User?

[Darin Johnson]

> | | is unix REALLY a multi-user operating system?  or does it just act that
> | | way because it is a multi-tasking o/s?  
> | 
> |   Any multitasking o/s can be a multiuser system, provided that the user
> | agent (shell or whatever) is a normal process.
> |   Note that this does not claim that any such o/s will work WELL for
> | multiple users ... 
> 
> Right! For example, OS/2 (ack barf) is a multitasking operating system
> that will never work very well for multiple users, simply because the
> assumption that there is only one user is so pervasive:
> 
>   --there is no concept of file ownership
>   --a single process, the "foreground" process, gets the largest slices
>     of cpu time because that's the one that the single user sees 
>   --the system assumes one keyboard, one mouse, and one monitor, and 
>     probably (I dont know this) assumes that the monitor is mapped
>     into main memory.

Similar problems exist for Amiga.  AmigaDOS is a fairly well built 
multi-TASKing operating system, but when you try to have multiple user's
you run into some problems.

File ownership is a problem, but isn't too severe (considering that you
normally only let good friends on :-).  The biggest problem is that a
requester will pop up on the screen for certain AmigaDOS 'notifications'
(such as 'please insert volume xx:').  There is a program to automatically
deal with these though.

Time slicing isn't a big deal, tasks have a normal concept of priority
(since a single user often sees >1 window there isn't a concept of a
"foreground process").

The most annoying problem though is when the user on the serial port runs
a window oriented program (some versions of Emacs, a game, etc.) causing
that to come up on your monitor.  In my case, the user has dialed in on
a modem using the only telephone line in the house, so it is a pain to
call up and tell him what he's doing wrong :-)  One of these days, I'll
write a talk program...

To summarize, here is a list of things that would make the Amiga a better
multitasking machine.  This probably applies to most multi-tasking machines
also. 

  1) the concept of "owning" the monitor, keyboard, and mouse.
     (don't let user's on serial ports own them easily)
  2) have programs know how to deal with stdin/stdout only.
     (for example, an Emacs program I use automatically pops up
     a new window to use, when it could easily just use ANSI terminal
     sequences)
  3) have enough programs and commands that don't use graphics/etc.
     so that user's can get along.
  4) a concept of "users".  This can be as simple as "login joe" ala
     Lisp machines, or can have passwords, etc.  Home directories, etc.
     would be nice.

There are some other items I could list, but they aren't really that major.

Darin Johnson (...pyramid.arpa!leadsv!laic!darin)
              (...ucbvax!sun!sunncal!leadsv!laic!darin)
	"All aboard the DOOMED express!"