How to list the files on a tape with tar?

Question

On a HP-UX OS I have a backup on a magnetic tape created from the SAM. Everywhere I read the instructions to list-verify the contents of the tape is to use the TAR program:

#tar tvf /dev/rmt/[tapefile]

I've created a new directory /tape with 777 permissions, but when I execute the above command it gives me an error message:

#pwd
/tape
#tar tvf /dev/rmt/0mn >> listtape
Tar: blocksize = 2
directory checksum error

Going after the blocksize error I used another version of the command with the "b" flag:

#tar tvb 2 /dev/rmt/0mn >> listtape
directory checksum error

Anybody have a sugestion? How can I view the contents of the tape? What does this error means?

Solution 1

I did solved this problem and I will post the answer here just in case anyone else have a similar problem.

Since the backup was created using SAM, TAR was NOT used to create the tape. More than likely 'fbackup' was actually used.

In order to see what is on the tape i should use the 'frecover' program.

This command will read the table of contents from the tape (/dev/rmt/0m) and write it out to /tape/tape.idx.

# frecover -I /tape/tape.idx -f /dev/rmt/0m

Solution 2

To see what format a backup is in you can use something like this:

dd if=/dev/rmt/0m of=/tmp/tapehead bs=1024 count=2
file /tmp/tapehead

I.e copy the first 2k from the tape to /tmp/tapehead and then run file on it to see what format it is.

This assumes that your /etc/magic file contains the given format description but even if not so, you might be able to identify the format using more, vi or od combined with Google. Some backup programs (Amanda for example) even includes a text file as the first file on the tape describing how to extract the tape.

Comments

[Zoredache]

Are you sure you have a tar style backup on the tape? Do you know what command was used to make the archive?

[Spirit]

Just "tar tv"? :o

[Philip]

Something ain't right... time to call HP I think.

[Spirit]

Just tried that. There is only one tar on the system that is /usr/bin/tar. I also rewind the tape as you suggested it still gives the same error. :S I even tryed to forward it on the first file using # mt -t /dev/rmt/0mn fsf 1.

[elbarna]

Is a notsense to rewind a non rewind tape? on 0mn n near "norewind"