Tape dumping programs for Unix/Linux...

From: Raymond Moyers <rmoyers_at_nop.org>
Date: Thu May 2 22:15:09 2002

On Thursday 02 May 2002 21:23, you wrote:

> No bad, just an honest difference in perspective. I recently went
> through this with a set of VMS-based diagnostics tapes. AFAIK, the
> tapes are undamaged, but dd returns a valid read - of the first file on
> the tape - and stops.

 and if you are using the /dev/nst0 device .. ( the one that dont rewind )

 then you repeat the command for the second file, dumping to a new file

 repeat for all the files on the tape, the last one i did this way, all
 the files spooled off the tape turned out to be Z compressed cpio
 archives that i could then extract the usual way

> I'm not that familiar with non-"streaming" formats, so I just accept
> what is without knowing why....

 Certainly less stressfull to accept and work around than to tilt
 at windmills ;=)

> dd on a disk or raw filesystem ignores files. On a tape archive, even
> using the raw device as the if, dd reads files and stops at the end of
> the first record.

 Yes.

> cat just dumped useless gibberish to a file.

cat dumps byte for byte exactly what comes off the tape, the "gibberish"
could be Z compressed for example

 use the
        file - determine file type
and see if it has a known magic number

> catting the file back to tape "should have" worked, right? Nope.

 No, but ... did you look at the mt command ?

 such as eof, weof Write count EOF marks at current position.

 After closing the write with the mt eof command it will probably work then.

 all with the nst0 non rewinding device that allows you to directly control
 things like tape position, and where at tape stop it will maintain this
 position.

 Raymond
Received on Thu May 02 2002 - 22:15:09 BST