Path: utzoo!attcan!uunet!convex!tedmonds
From: tedmonds@convex.com (Tracy Edmonds)
Newsgroups: comp.sys.ncr
Subject: Re: Need help booting dual operating systems
Message-ID: <104178@convex.convex.com>
Date: 22 Jul 90 17:46:57 GMT
References: <467@mtndew.UUCP>
Sender: news@convex.com
Organization: Convex Computer Corporation; Richardson, TX
Lines: 52

In article <467@mtndew.UUCP> friedl@mtndew.UUCP (Stephen J. Friedl) writes:
>Hi folks,
>
>     I don't get this group [yet] so forgive me if I'm jumping in
>the middle of a flamefest or anything.  We are porting our fax
>software to lots of different machines, and NCR has generously
>loaned us a Tower 32/650 to do it on.  We have tapes for System V
>Releases 2 *and* 3, and we have calls for software running on
>both.
>
>     Is it possible to load both versions of the OS onto the hard
>drive and boot one or the other easily?  If we have to reload
>from tape every time we need the other one it will clearly drive
>me crazy.
>
No.  There is only one rootable/bootable file system per disk.  However,
There are some possible other options: 
1) I believe it is possible
to boot the V.3 kernel on a V.2 root file system (this may also require
both versions of /etc/init).

2) If your release specific calls are not related to the kernel then
you can place an alternative root file system in a subdirectory
and simply do a chroot.

>     I suppose we could do it with a pair of drives and just boot
>off the appropriate one, but I'd like to try to do this off of
>one internal drive (a 300MB Maxtor SCSI drive).  I have
>partitioned the drive into a pair of 150MB partitions (numberred
>1 and 2) and loaded Sys V Rel 2 onto the first one.
This would be the best way to do it.  In this case you simply make kernels
for each with the rootdev swapdev etc. set appropriately and then set the
manual auto switch on the top of the unit to manual.  When booting up through
SUS you simply specify "h501 or h502".

>
>     I have hunted around for where the partition tables are located,
>and while I have an idea on this, I don't know how to mark a partition
>as having containing the root filesystem -- perhaps it's always the
>first one.  If I hacked around at this for hours and hours I could
>probably figure it out, but that is a very long road to go down for
>what is not our primary platform.
Just use the dkpart command to browse at the partition tables and/or
change them.  Read the man page first.  Also these functions can be performed
nicely through VA.

-tracy

Tracy Edmonds
Convex Computer Corporation
tedmonds@convex.com
(214) 497-4753