Tape Devices

[Shannon Petry]

I have a tape that someone made on a old AIX system, which I can not read. If my memory serves me correctly, the AIX system used byte swapping on the Tape device, and thus the inability to read on a HP-UX system.
How do I create a byte swapping device file so that I can read this tape? I used to do this looong ago, but can not find my notes anywhere.>

Thanks in advance!
Shannon

[A. Clay Stephenson · Accepted solution]

Hi Shannon:

You use your old friend dd.

Something like this:

dd if=/dev/rmt/3m bs=512 conv=swab | tar xvf -

You may want to play with bs a bit or do 1 dd with large input blocking which in turns pipes to another for the conv=swab.

[Michael Tully]

Hi,

You could also use 'pax' if you don't know what format the tape was originally cut in.
'pax' can read both tar and cpio tapes.

-Michael

[Marco Paganini]

Hello,

I'm not absolutely sure at this point, but GNU cpio was able to read pretty much ANYTHING you fed it, including tar files, zip files, etc, etc. I'd say they have an option to byte swap the data. BTW, I'm assuming you used cpio, tar or something like that to make the backup.

Regards,
Paga

[Frank Slootweg]

Building on Clay's response:

If you do not know the tape format, then may be reading one record and inspecting it with file(1), xd(1), etc. might help, i.e.

dd if=/dev/rmt/... of=/tmp/record bs=64k count=1 [conv=swab]

file /tmp/record

xd -bc /tmp/record | more

etc..

[Darrell Allen]

Hi Shannon,

Already mentioned: dd, pax (which covers tar and cpio). What about dump?

Darrell

[harry d brown jr]

Shannon, I don't think AIX is a byte swapped machine, but then again that was eon's ago. What error message did you get trying to use tar or cpio? Also, can you show us the "magic number" by doing this:

dd if= bs=1 count=100 | od -bc

From the "magic number" we can easily determine if it is byte swapped and what kind of tape it is.

live free or die
harry