topic Re: restore partial overwritten tape in Operating System - Tru64 Unix

restore partial overwritten tape

iliviu — Fri, 18 May 2007 05:46:58 GMT

Hello .
I have a tape containing severeal vdump sessions. Accidentaly I forgot to seek the end of tape before starting a vdump session. So I wrote a new session from the beginning. Since each session is aprox. the same size (I probably lost max 2 sessions), I expect to find a method to recover some sessions, since they were not overwritten. Do you know a simple way ( without using the services of a professional recovery lab) in order to achive this ?

Thank you
Liviu

Re: restore partial overwritten tape

Rob Leadbeater — Fri, 18 May 2007 07:05:10 GMT

Hi,

You should be able to forward through the sessions with mt fsf

So...:

mt -f /dev/tape/tape0 rewind (to get to the start of the tape)
mt -f /dev/ntape/tape0 fsf 1 (to go forward a session)

Then use vrestore to see what's on the tape...

I've assumed your tape device is tape0. If not change it appropriately.

Hope this helps,

Regards,

Rob

Re: restore partial overwritten tape

iliviu — Fri, 18 May 2007 07:22:13 GMT

The problem is the EOM (End of Medium). The drive doesn't pass over this mark. Right now I am trying a trick to write over the EOM mark. Any idea is still much appreciated.
Thank you.

Re: restore partial overwritten tape

Vladimir Fabecic — Fri, 18 May 2007 08:20:04 GMT

There is a hacker "way" how to pass EOM.
1. Forward tape to stop at OEM
2. Create a large "junk" file, about 100MB
3. # tar cvf /dev/ntape/tape0 junk_file
4. Start writing this file to tape, but interrupt the writing an EOM mark by powering off the tape drive (after 15 seconds)

Doing this new EOM will not be written.