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From: guy@sun.uucp (Guy Harris)
Newsgroups: net.unix-wizards
Subject: Re: Multiple Unix Universes
Message-ID: <5735@sun.uucp>
Date: Fri, 1-Aug-86 14:41:25 EDT
Article-I.D.: sun.5735
Posted: Fri Aug  1 14:41:25 1986
Date-Received: Sat, 2-Aug-86 10:45:16 EDT
References: <2707@brl-smoke.ARPA>
Organization: Sun Microsystems, Inc.
Lines: 30

> There is a 100% solution, though as far as I know no one has actually
> implemented it yet.

It's not clear handling the S5/4.2 differences by running them as guest
operating systems under some hypervisor (whether UNIX or something else)
would be a win.

For one thing, it's kind of gross to go through all that work to get around
differences that are relatively minor.  The user would, again, have to
manage two sets of administrative utilities; why should they learn about
another version of "init" just so that somebody can run a shell script that
requires different behavior from "tr"?

For another, would "open" be treated as a virtual machine instruction (so
that the file system code is part of the hypervisor) or would you provide
minidisks to each of the "guest" operating systems?  In the latter case, it
may be a pain to share file systems; that much partitioning would render
this scheme useless.

Also, you'd have to partition the terminal ports somehow; either a given
terminal port is always assigned to one virtual machine (which loses for
dial-up ports) or you'd have to have a command that the hypervisor's handler
for ports recognizes, so you can connect to the desired one.

The notion of UNIX as a hypervisor is interesting; it's not at all clear
that this is an appropriate use for it, though.
-- 
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com (or guy@sun.arpa)