[NCLUG] Tape extraction help needed.

[Michael Dwyer]

Erich wrote:
> I have some tapes containing data grouped into header and
> image files.  Using dd, I can get the header file, but it
> then terminates, and the remainder of the data (~130MB) is
> ignored.  Am I doing something worng?
> 
> 
>>dd if=/dev/st0 of=tape2 bs=16k
> 
> 0+1 records in
> 0+1 records out
> 
> Does anyone know of another utility to simply dump data
> from a tape to a file?  (cpio is doing the same as dd right
> now).

If my understanding is correct, the tape can be sort of broken up into 
'files' and 'records' -- at least, as much as one can do that on a tape. 
  vis, the mt(1) man page.  I think you would probably do something like 
this:

   mt /dev/sg0 rewind
   dd if=/dev/st0 of=tape1 bs=16k
   mt /dev/sg0 fsf 1
   dd if=/dev/st0 of=tape2 bs=16k
   mt /dev/sg0 fsf 1
   ...

If 'fsf' (= Forward Space File) doesn't work, maybe 'fsr' (= Forward 
Space Record) would work.  Also, be aware that the mt control device 
might be different than the data device.  eg, turn on the write 
protection on these tapes NOW, in case you do something like I did
(= stupid) and overwrite the tape header...

/usr/src/linux/Documentation/ftape.txt might also have some 
enlightenment for you...