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From: hedrick@topaz.RUTGERS.EDU (Charles Hedrick)
Newsgroups: net.unix-wizards
Subject: Pyramid system design
Message-ID: <5446@topaz.RUTGERS.EDU>
Date: Tue, 29-Jul-86 03:07:41 EDT
Article-I.D.: topaz.5446
Posted: Tue Jul 29 03:07:41 1986
Date-Received: Tue, 29-Jul-86 07:36:07 EDT
References: <1759@brl-smoke.ARPA> <976@decuac.DEC.COM> <459@oracle.UUCP> <5431@topaz.RUTGERS.EDU> <5561@sun.uucp>
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 41

Guy Harris expressed disbelief that Pyramid could possibly have
complete 4.2 and System V universes.  I have no idea whether it is
possible or not.  I can only say that they have done it.  Their kernel
has a full set of 4.2 and SV system calls.  This is not a case of an
emulation package being done at the library level.  By and large they
have a full set of 4.2 and SV utilities.  There are a few cases where
this is not true.  E.g. the compilers are usually the same (but the
libraries are not, of course.  So the compilers produce real ATT
programs on the ATT side and real UCB programs on the UCB site.)
Also, you get a real UCB C shell even on the ATT side.  (This is in
some sense a violation of their design philosophy.  Presumably they
decided that supplying a C shell where ^Z is intentionally disabled is
carrying purity too far, particularly since csh isn't really part of
SV anyway.  There are separate Bourne shells.)  But most things come
in both Berkeley and ATT flavors, even things like ps and who.  (They
actually have separate wtmp's and utmp's, both of which contain data
for all of the jobs.)  There are separate line printer spoolers (which
can run at the same time, and I think may even be able to share the
same printer), UUCP's, and mail programs.  Presumably one could have a
site that had two different UUCP site names, going to the two
universes.  My guess is that almost all sites run one or the other
version of UUCP.

I don't know the exact reason for doing all of this, but I can guess.
There are certainly commercial accounts who don't want any of this
Berkeley stuff.  There are Universities who have no interest in ATT.
There are also middle of the road places that would like to be able to
choose a particular mix of UCB and ATT features that is appropriate
for their site, and maybe develop programs for both Berkeley and ATT
Unix with some hope that they will really run on each kind of
implementation.  It is also possible to mix things, so that you can
use Berkeley job control in a program that uses SV locking, etc.

As for init, yes there are two inits.  Of course you don't run them
both at once.  But the system administrator gets to choose which one
he wants.  They each read the set of startup and configuration files
that you would expect for that version.  init and login are the
primary places where you can't have both universes active at once.
However the logins each know how to deal with both universes.  They
can each start jobs in either universe.  (The user can choose which he
wants.)