bmw@aesat.UUCP (Bruce Walker) (01/21/85)
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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!bmwdtynan@cadvax (Dermot Tynan) (02/02/85)
[***** Eat your heart out! *****] /* --->> From bmw@aesat.UUCP (Bruce Walker)... 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. */ Ummm, you seem to be missing the point... Single-User in this sense, does not mean that only one person has access to the system (one "entry" in the passwd file). It means that it cannot process several jobs at once. Granted, the IBM PC has the ability to run several *processes* belonging to the same user, the capability of context switching with regard to several users is a bit trickier. The CPU does not have the capability to block illegal memory accesses (PAGING/VM), nor the speed required for multi-user. In the words of the immortal bard: "One cannot win the INDY500 with a honda civic, but one *can* try". Running a few *dumb* background processes (like printer spooling) and executing several user programs at once is like comparing chalk and cheese. Your best bet is to put UN*X on a crash diet, and bring it down to something that will run efficiently on an 8-bit bus (IBM PC). The first step is to cut out *anything* that resembles multiuser, then start trimming functions. I hope this *bare* account of the problems helps you see the difference. No doubt I will be attacked for my over-simplification. If you have any questions, you know my mail-slot... In summary, the *main* advantage of UN*X on a PC is that ONE person can use it's capabilities. If you REALLY want to save $$$$, and have more than one person use the system, try buying a Charles River Data Systems, 68K system. It runs an operating system *close* to UN*X, called UNOS. I can't comment on how good or bad UNOS is, in relation to UN*X, but I do know the hardware is >>excellent<<!!! - Der (Tynan) cadvax!dtynan "May the blessings of Jeyes Fluid fall upon you"