How to Read data from DLT tape

[Leah Chow]

I had a problem mounting a DLT tape to read data from it. Since it is very old tape, we even don't have the veritas machine which created the tape. Does someone give me some idea how to get the data out from the tape? The sever is old too, it is hpux 11.00.

# mount /dev/rmt/0mn /tape
mount: /dev/rmt/0mn is an invalid operand

Below is the ioscan output:

# /usr/sbin/ioscan -funC tape
Class I H/W Path Driver S/W State H/W Type Description
======================================================================
tape 0 10/4/3/0.2.0 stape CLAIMED DEVICE HP C1537A
/dev/rmt/0m /dev/rmt/c5t2d0BESTn
/dev/rmt/0mb /dev/rmt/c5t2d0BESTnb
/dev/rmt/0mn /dev/rmt/c5t2d0DDS
/dev/rmt/0mnb /dev/rmt/c5t2d0DDSb
/dev/rmt/c5t2d0BEST /dev/rmt/c5t2d0DDSn
/dev/rmt/c5t2d0BESTb /dev/rmt/c5t2d0DDSnb


Thanks a lot

[Torsten.]

You cannot mount a tape like this.

Depending on the archive type, you will need a sufficient command to read the data, like

tar
frecover
cpio
dd
...

[A. Clay Stephenson]

Mount only applies to filesystems and HP-UX does not support tape-based filesystems. The tape drive you are displaying via ioscan is a DAT(DDS) drive. If this is an ioscan of the machine you are referring to then no DLT device is displayed. The first thing you will need to do is make the tape drive visible to the box. You may be connection an LVD/SE SCSI drive to an HVD bus in which case it will never work.

Once ioscan sees the device as "CLAIMED" you will also need to run insf to create the device nodes. Having done this, your troubles may just be beginning because if Vertitas software was used for backup then you will need a compatible version of Veritas software to read the data.

[Torsten.]

In fact, your drive is not a DLT drive, this is a DDS3 (connected to a K-Class?).

[Jannik]

Hey,

The commen way of backup types are:
- fbackup/frecover
- cpio
- tar
- dump/restore
- vxdump/vxrestore
- pax

to restore - examples:
# frecover whith a graph file : gfile
frecover -x -v -f /dev/rmt/0m -g gfile
# tar normal
tar -xvf /dev/rmt/0m

Regards,
Jannik

[Leah Chow]

I tried to recover the data to the server, used these two commands to test:

# tar -xvf /dev/rmt/0m
Tar: blocksize = 16
directory checksum error
# ls -rlt
total 0
# frecover -x -v -f /dev/rmt/0m
sh: frecover: not found.
# /usr/sbin/frecover -x -v -f /dev/rmt/0m
frecover(5419): checksum on volume header is incorrect.
frecover(5420): not an fbackup volume; magic value is incorrect
frecover(2105): did not find expected file marker
frecover(5412): Do you wish to try to salvage this volume? (^[yY]/^[nN]) n
frecover(5411): Do you wish to try a different volume? (^[yY]/^[nN]) n
frecover(5414): abort selected

both of them don't work.

[A. Clay Stephenson]

Since your "DLT" tape has magically transformed itself itno a DAT/DDS tape, at least, we know you have a working tape drive. Now we need to find out what kind of backup image is on the tape. Let's read off the first parts of the tape and translate it into human-readable form so that we can possibly see magic numbers or other characteristics that will identify the format (although I suspect Veritas Netbackup based upon your earlier data).

Do this:

dd if=/dev/rmt/0m bs=512 count=2 | od -v -Ad -tco > /var/tmp/f1

Next post the file, /var/tmp/f1, and someone may be able to identify the backup format.

[Leah Chow]

Here is the attachment file of /var/tmp/f1

Thanks

[A. Clay Stephenson · Accepted solution]

You only posted 1 block of output (and this may simply be a 512 byte label) but among other things the word "Seagate" appears. This strongly suggests that this is the label for a NetBackup or BackupExec tape. You should note that NetBackup was later acquired by Veritas and was then, in turn, acquired by Symantec. Perhaps someone with more familiarity with NetBackup and BackupExec can be of further help but this is not going to be a standard UNIX restore using tar, cpio, etc. Your best bet may be to contact Veritas/Symantec support and send them the od output.

Almost certainly, there are additional images beyond this tape label that you can access using dd and the norewind devices. The mt command can also prove useful to skip past filemarks although multiple dd's using norewind (/dev/rmt/0mnb) is perhaps a better approach.

[Doug Burton]

It's been a while but I remember something about Veritas using there own version (?) of tar located at /usr/openv/netbackup/bin/tar. If the files have not been encrypted on the tape you *may* be able to get data off the tapes using this file. However, you said you don't have "the veritas machine" anymore. You may want to get a hold of Veritas and see if they have a "light" version of there software or some other method you can use in order to grab that data.

[Leah Chow]

I tried to find netbackup folder, but i couldn't, so i guess i just need to call Veritas, ask them for help. Thank you for all your help.