From: ignatz@chinet.chi.il.us (Dave Ihnat)
Subject: Re: How to get Merge to see DOS partition?
Summary: I went through this dance, too.  It works, with work...
Organization: Chinet - Public Access UNIX
Date: Mon, 14 Dec 1992 21:17:37 GMT

In article <1992Dec9.165909.19109@sbcs.sunysb.edu> shane@cs.sunysb.edu (Shane Bouslough) writes:
>I have Dell UNIX on a disk which also has a bootable DOS
>partition. According to the Merge docs, the DOS partition
>should appear as e:. Unfortunately it doesn't.

Nope.  Not as it comes from the installation scripts.

>I created the DOS partition after I installed UNIX, so I
>can see how this would be a problem. However, I can't seem
>to find a way to get Merge to find it now. dosadmin seems
>to be of no help. Any ideas? Sorry if this is in the Merge
>docs, I couldn't find it.

I went around a couple of times with Dell support, but they don't use this
much, I gather, since I got a couple of answers that turned out to be incorrect.
(Specifically, that /dev/dsk/0s5 is recognized as a special DOS partition
by the disk driver.  Behavior on the (finally) working system belies this
assertion.)  No problems--they tried to help, but I didn't want to keep knocking
on their door on what was, essentially, a solvable problem.

You state that you created the DOS partition after you installed UNIX, so I
assume that you reserved some disk space for it.  (Otherwise...naw, let's not
go into that.)  In my case, I created the DOS partition on installation of
the DELL system; from your behavior, it is likely that the same problem
occurs in either case.  There is never a valid entry in /etc/partitions
for the DOS partition.  That is, for the kernel to interpret /dev/dsk/0s5
properly, there must be an entry in /etc/partitions (or, more appropriately,
the VTOC written from that file) to tell it the starting and ending locations
of this partition on the full physical disk.  You have to calculate these
values and create that entry in the partition table.  Another caveat here--
the disk0 (or disk1) total size doesn't reflect the DOS partition; ONLY the
total of the UNIX-utilized partitions.  Thus, the total space on your disk
will consist of the sum of the UNIX partitions, which should be reflected
in the totals given by the disk[01...] partitions file entry; plus, any
DOS partitions you've reserved.  The implication from this discovery was
that I should be able to support multiple DOS partitions, but I've not
tried this.

Finally, there does seem to be some strangeness in the way MERGE uses
its /etc support files (dosapp.dev,dosenv.dev) Although entries are there
for both the mouse (on COM1) and /dev/dsk/dos--which is just another special
device with the same major,minor numbers as /dev/dsk/0s5--neither are
automatically available when you crank up DOS; to get either (or both), the
command line options must be explicitly given on startup:

	dos +adcom1 +ae:=/dev/dsk/0s5

More, although /dev/dsk/dos and /dev/dsk/0s5 have the same major,minor numbers,
I can't access the partition from /dev/dsk/dos; it has to be the 0s5 special
device.  This latter may well be a configuration problem, however, as none of
the MERGE manuals are available from Dell, and the online manuals are one rev
out of date.  (Any ideas how to get the latest version of the manuals?)

Finally, be careful; there are some internal notes and comments about the
MS-DOS FDISK utility zonking the partition table WRT the format that Dell
expects.  I experimented a bit with this, and didn't encounter any problems,
but caveat utilitor.  In any case, while it takes a little work with a
calculator, the alternate boot partition does work well.  I can boot from
either partition, and access the DOS partition under MERGE with no problems.
Remember to do a 'dd' backup of that partition when you do your normal Unix
system backups, unless you intend to do a DOS-level backup...

Cheers,
--
		Dave Ihnat
		ignatz@homebru.chi.il.us (preferred return address)
		ignatz@chinet.chi.il.us
Newsgroups: comp.unix.sysv386,comp.unix.questions