Tape Duplication Procedure Needed

[t patterson]

Reply-to: tp at decwrl.UUCP (t patterson)


In article <85740 at felix.UUCP> stern at imagen.UUCP (Martin Stern) writes:
>Hi Everyone,
>	I have a question concerning tape duplication of an Ultrix 
>installation tape. I want to back up my Ultrix distribution tape
>(it turns out that it wasn't bad at all !!) just in case of disaster
>so i tried the following command
>
>	%dd if=/dev/nrmt9 bs=5120 of=ddfile
>
>and received
   [errors]
>My question is: How do I make a backup copy of this tape ?

as this may be of general interest, am posting this reply also.

Ultrix 3.0 actually has documentation which helps describe the format of
its installation tape ("Guide to Preparing for Software Distribution on
Ultrix Systems"). however, the /etc/setld script is _still_ the
easiest way to figure this out (plus entertaining and educational).

(I figured out all of the following at Intel using "dd" and reading
"/etc/setld"; insert standard disclaimers here.)

your main problem is that the tape consists of multiple files. so, some
succession of dd commands (or something) is needed to read it.

what I usually do is:
	dd if=/dev/nrmt0h of=file.0 bs=512
	for i in 1 2 3 4 5 6 7 8 9 ... [lots of numbers here]
	do
		dd if=/dev/nrmt0h of=file.$i bs=10k
	done

there is also an ordering to the files on the tape:
	file 0:  used to be boot block, 512 bytes; seems like they usually
		 give out a separate standalone tape nowadays, so this is
		 probably obsolete (it had nothing interesting on it when
		 I looked at the Ultrix 3.0 tape).
	file 1:  my memory may be fooling me, but I think this used to be
		 the standalone kernel; again, a space was left here on the
		 3.0 tape
	file 2:  mini-root filesystem in dump format
	file 3:  all the control files for the rest of the distribution in
		 one big tar file
	file 4:  all the rest are compressed tar files (think they first  
	   .     started compressing them in 3.0); you can figure out how
	   .     many there are by reading file 3, but I'm usually lazy and
	file n:  just keep dd'ing until there's nothing left to read.

anyway, the first two files don't seem real important anymore, so you could
probably get away with a big loop which just dd'd files off the tape until
it bombed. you can also use the /etc/ris program to get stuff off the
tape. (using ris is a decent idea if you want to keep the tape contents
on-line and do installs to other systems over your network.)

and, of course, after you've dd'd the data to disk, you can dd it back to 
a tape at your leisure ... or dd from tape to tape if you can. once you
know the tape is arranged you can handle it any way you want.
--
t. patterson		domain:	tp at decwrl.dec.com    path: decwrl!tp
			icbm:	122 9 41 W / 37 26 35 N
% opinions herein are mine alone and certainly not those of DEC