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From: jerry@heyman.austin.ibm.com (Jerry Heyman)
Newsgroups: comp.unix.aix
Subject: Re: PCSIM on RS6000
Message-ID: <5131@awdprime.UUCP>
Date: 5 Feb 91 19:20:14 GMT
References: <63457@brunix.UUCP>
Sender: news@awdprime.UUCP
Organization: IBM Austin, TX
Lines: 46

In article <63457@brunix.UUCP> lr@cs.brown.edu (Luigi Rizzo) writes:
[... description of setting up simulated drives in PCSIM ...]
>
>In order to let several users run their DOS application without
>waste of disk space, I would like to use a unique, possibly read-only,
>copy of the C_file, containing all the standard programs and files,
>and let each user have her/his own D_dir with all the specific
>application programs and data files.

It is possible to do so, by changing the mode on the C_disk file to 444 (making
it read-only for all users).  This works fine, unless you have programs that
MUST write to the C_drive - they will fail.

>However, it looks that this approach is not possible, at
>least in a straightforward way, because:

>
>1) the PC simulator creates a lock to signal that a C_file is
>   currently used by a simulator process, and refuses to use it if
>   it is busy.
>
>2) Programs cannot be run from a D_dir.
>
>I cannot really understand why these restrictions are present.
>

1) If the C_drive is read-write, then it will be file-locked to protect the
user from having someone else mangle the files in that simulated hard disk
while they're running.

2) There is a restriction on executing from a directory (see the documentation)
on v3.1 PCSIM.  This is an area that is being corrected for a 'future' release.
There is nothing stopping you (or any other user) to have a second AIX file as
the D_drive and making it read-write so that each user can share there.  The
problem is just the C (boot) drive.

>
>	Luigi Rizzo
>	lr@cs.bronw.edu, luigi@sssup2.sssup.it

jerry
-- 
Jerry Heyman                     IBM T-R: jerry@heyman.austin.ibm.com
AWD Tools Development            VNET   : HEYMAN at AUSVMQ
AWD Austin                       T/L    : 793-3962
*** All opinions expressed are exactly that - my opinions and NOT IBM's