I have a tar archive which I believe may be corrupted, produced on an HP-UX 10.x box and written to a 4mm DDS-3 tape.

I understand that gnu tar has a -W (--verify) option which will attempt to verify the archive after it has been created. Am I right in saying that this option cannot be used to verify an existing archive?

Secondly, the native shipped HP tar does not include this verify option at all. Does there exist a program for verifying the integrity of tar files (written to a tape), either whilst creating the tar file or after the event?

As a foot note I must point out that this archive has never been gzip'ed.

Thanks for any input...

Take a table reading off the archive

tar -tvf [tarfile]

I have not yet known a tar archive that gives a valid table that does not restore without any problems. Redirect the output to a file if it is a large archive and you need to examine the table more thoroughly.

Regards.

When I attempt this I get an error message:

Tar: blocksize = 2
directory checksum error

Now a few things are leading me to want to verify the archive rather than assume that the media is shagged:

(1) The filesystems backed up onto this tape have very long path and file names

(2) The system has not been patched for an age.

(3) Previous sysadmins for these boxes (I inherited them 3 weeks ago) have apparently performed successful restores in the very recent past

Therefore I just want to make sure that the archive is not crocked before I write it off.

For everyone's info: you _can_ apparently verify an existing archive with gnu's tar: www.gnu.org

Cheers.

If you're not getting a table off the tar file and there is a checksum error it's probably the archive which is corrupt - however it could be the media. Either way you're not going to be able to restore from it, why don't you try creating the archive again? Other than working out if you are going to use this tape again or not, I can't see any other reason for you wanting to find out whether the archive or the tape is messed up.

You could spend a fortune and send the tape to HP's storage recovery labs for them to take a look, but try getting that past your line manager

Regards.

More curiosity than anything - I'd just like to understand _why_ it went wrong - might even learn something