Summary: Recovering files from a tar tape whose header got overwritten

Hi,

Summary is that for recovering from this tape you need special hardware that
read past EOM (end of media)
mark in the tape.  For that we need to take help of data recovery companies.
In short, data cannot be
recovered using the Unix tools and standard tape drives we have.

Lesson learnt is, always make sure to write protect the tape when you are
doing restore.

Thanks to 'A Darren Dunham', 'francisco roque' and 'the hatter'.

Regards,
Subin Hameed
---

-----Original Message-----
From: Subin Hameed (HO - IT Dept)
Sent: Monday, May 11, 2009 3:39 PM
To: 'sunmanagers@sunmanagers.org'
Subject: Recovering files from a tar tape whose header got overwritten

Hi,

I was supposed to restore from a tar backup tape with a single tar archive of
8 files on a Solaris 9

server with DAT 72 internal tape drive.

But I accidently used this command "tar cvf /dev/rmt/0 /backup/file2.dmp.Z"
instead of

"tar xvf /dev/rmt/0 /backup/file2.dmp.Z".   The filename I gave as argument
was a non-existent

file and also I immediately did a control C and stopped the write.
Surprisingly, I don't see any contents

on tape though the tar command was wrong (only file argument I gave was a
nonexistent file) and I did

control C almost immediately.

I think tape EOM mark got written to beginning to tape, but rest of data is
intact.  Can someone help me

on how to recover this data.  I need only a single file from the tar archive,
I see from later backup logs

that this file is the 7th file in the tar archive.

Is there any way to make a copy of the entire tape, so that I have  a copy of
this tape if I have to do

some write operation for recovering data.  I mean a different kind of dd,
which will not search for end

of media records so that I can copy entire tape.  Appreciate any help and
thanks in advance.

I am pasting screenshot of what took place:

------------------------------------
# tar cvf /dev/rmt/0 /backup/file2.dmp.Z
tar: /backup/file2.dmp.Z: No such file or directory
^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C#
# tar tvf /dev/rmt/0
# mt status
HP DAT-72 tape drive:
   sense key(0x0)= No Additional Sense   residual= 0   retries= 0
   file no= 0   block no= 0
# mt eom
# mt status
HP DAT-72 tape drive:
   sense key(0x0)= No Additional Sense   residual= 0   retries= 0
   file no= 1   block no= 0
# tar tvf /dev/rmt/0n
tar: blocksize = 0

--------------------------------------

Regards,
Subin Hameed


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