[TUHS] Unix v7 tape drive question

[Clem Cole]

On Thu, Mar 2, 2023 at 9:28 AM KenUnix <ken.unix.guy at gmail.com> wrote:

> Hi,
>
> I am trying to use the 'dump' program but it references rmt1.
>
> My system only has rmt0. I have been unable to find how to
> create this device. I have looked over the reference material
> but it only references rmt0.
>
> Is there any way to redirect a dump to use rmt0?
>
Some thoughts...

1.) start with the man page: https://man.cat-v.org/unix_7th/1/dump
You note the first key parameter described is f - i.e. dump fu0 /dev/rmtXXX
/dev/rrpY

Remember on traditional research systems like V6/V7you should use rmtX and
rrpY not mtX and rpY as you don't what to use the buffer cache (modern
UNIXs & Linux use the paging HW so things like need for the old I/O buffer
cache are avoided).

2.) next: read: https://man.cat-v.org/unix_7th/4/tm

cd /dev; ls -l *mt*
(if you type: cat makefile that would not hurt)

I suspect you will see three devices: mt0 (a blocked device i.e. thru the
buffer cache and then copied in/out to your program) and two raw devices:
rmt0 and nrmt0 (character devices i.e. direct I/O to your program).    Using
mknod create the next Unit number - i.e. three more device files: mt1 rmt1
and nrmt1   - don't forget chmod them too

Now with simh, you can add:  attach tm1 some_local_file

3.) since you are using simh, you could also use the RH11/RH70 based Tapes
which are the ht devices: https://man.cat-v.org/unix_7th/4/ht
The makefile in dev will create 2 drives for you and make sure you use a
UNIX kernel configured with the ht driver included.
Also in simh, enable TU0 and TU1 instead of TM0 and TM1

I would not recommend recompiling the tape utilities, although as Dan said
you could do that.


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