[Simh] Attach tar to tape device and access it from v7 in simh

[Will Senn]

Hi,

I think I may have asked this a couple of years ago, but I am unable to 
find the email conversation, so I'll ask it again from a position of 
experience and greater but still lacking knowledge... here's the 
background - I am running a v7 instance in simh that I am quite pleased 
with. However, I saw somewhere where someone was running some additional 
software on their instance and of course, I just had to have it for my 
own. Unfortunately, it's not clear how they got the software, where it's 
from, or how they got it running. There are hints that the stuff came 
from early bsd. So... I thought I would try getting the bsd source on to 
my v7 instance to see if I could compile it and play around with it. 
There's a 1bsd.tar.gz in the tuhs archive. It being a tar file, I 
figured I could:

gunzip 1bsd.tar.gz

in simh:

att mt0 1bsd.tar

in v7, which defaults to mt1 for some reason, (not a configured device 
on my system and isn't created by make tm in /dev):

tar vxfb /dev/rmt0 1
nboot.ini-13> boot rp0

Invalid magtape record length, PC: 002400 (MOV 177776,R0)

or

tar xv0

nboot.ini-13> boot rp0

Invalid magtape record length, PC: 002400 (MOV 177776,R0)

I don't know why the nboot.ini-13> boot rp0 artifact is appearing 
(prolly some buffer flush when the sim aborts)... but of more concern is 
why I can't access the tar. I'm sure it is a gap in my understanding, so 
I'd appreciate some help.

Thanks,

Will