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From: rwhite@nusdecs.uucp (Robert White)
Newsgroups: comp.unix.sysv386,comp.unix.xenix.sco
Subject: Re: booting DOS on ISC+SCO, and DOS filesys handling (long-ish)
Message-ID: <1991Apr30.175653.22682@nusdecs.uucp>
Date: 30 Apr 91 17:56:53 GMT
References: <1991Apr24.074220.17639@jet.uucp> <1991Apr27.053546.1461@rushpc>
Organization: National University, San Diego
Lines: 49

I know that on the SCO system we have here you when you see

boot
:

You can type "dos<cr>" and dos will boot.

For my system at home <jagat> I have use the pfdisk program
that was posted on the net some time ago.  I still have the
source archive (and I have compiled them for ms-dos but I
never did get it to work from the unix side).  The program
works great!  It replaces the harddisk boot sector program
with one of two others.  BOOTAUTO or BOOTMENU.  BOOTMENU
*always* gives you a menu of your partitions and you select
the one from which you want to boot.  BOOTAUTO will boot
from the currently active partition unless you press a
key within about 5 seconds of getting the "boot device h0"
message;  when you press a key you get the menu.

I use AT&T SVR3.2.1(1) and MS-DOS 3.30a and BOOTAUTO.  I have
placed a timeout in the "save the dump space" question in
the boot sequence so that my UNIX system will do a complete
reboot unatended if the power goes out.  When I need DOS
I do a telinit 0, *HARDWARE RESET*(2) and a "<space>3"(3) at
the prompt.  What could be easier.

If you need it (source or source and uuencoded binary for ms-dos)
mail me at crash!jagat!rwhite (or rwhite@jagat cause I'm in the
maps but the path there now just a tad longer than the direct
method) and I'll send them out.  (NO WARENTEES  I didn't write it
but it does work for me.)

(1)  Due to an oddity in the boot program for this release of
UNIX System V the UNIX partition *must* be the active partition
when booting.  the boot program dosn't use dynamic boot information
it gets the stats directly from the partition table.

(2)  Alwasy do a hardware reset when switching between UNIX
and MS-DOS.  There is no standard for software reset in a PC
compatible system so a soft reboot may not properly clear
states from your hardware.  Most notably serial ports and
tape drive software may not completely understand the state
of the device left over from the other OS.

(3)  For some stupid reason the PC allocates partition slot 4,
then 3, then 2, and then 1.  Yep.  They are backwards.  Go
figgure.  8-)

Rob.