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From: wescott@Columbia.NCR.COM (Mike Wescott)
Newsgroups: comp.sys.ncr
Subject: Re: Need help booting dual operating systems
Message-ID: <2239@sauron.Columbia.NCR.COM>
Date: 23 Jul 90 18:36:14 GMT
References: <467@mtndew.UUCP>
Sender: news@sauron.Columbia.NCR.COM
Reply-To: wescott@micky.Columbia.NCR.COM (Mike Wescott)
Organization: E&M-Columbia, NCR Corp, W Columbia, SC
Lines: 42
X-Local-Date: 23 Jul 90 11:36:14 PDT

In article <467@mtndew.UUCP> friedl@mtndew.UUCP (Stephen J. Friedl) writes:
>      Is it possible to load both versions of the OS onto the hard
> drive and boot one or the other easily?

Yes.

>      I suppose we could do it with a pair of drives and just boot
> off the appropriate one,

The easiest and most obvious way but not necessarily the most efficient
use of resources ...

> 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.

A good start.  What you need to do is make a filesystem on the second
partition and copy everything to it.  Then remake /unix so that the
rootdev is also partition 2, save this on the second partition.

Now install SysVr3 release onto the first partition.  When done
mount the second partition read only and copy the second partition's
unix to /unix.r2 and unmount.  Link /unix to /unix.r3.  Then boot either
/unix.r2 or /unix.r3.  If you remake the r2 kernel remember to copy it down
to the first partition (you may have to boot the r3 kernel to do this).


AN ALTERNATE METHOD:

It possible to tell the boot program the start address of the partition
in which it will find the kernel.  With this in mind we can put the
r2 root filesystem and kernel (with rootdev spec'd as partition 2) on
the second partition and leave the r3 system on partition 1.  You
then boot in manual mode and tell SUS to boot from "/unix" if you want
to use partition 1 and tell SUS "/unix of312200" if you want to use
partition 2 (assuming that partition 2 starts at block offset 312200).
Some older Towers use a different syntax, "/unix;312200" I think.

--
	-Mike Wescott
	 mike.wescott@ncrcae.Columbia.NCR.COM