topic Re: Question about to show the content of an DLT-tape? in Operating System - HP-UX

Question about to show the content of an DLT-tape?

ekke2 — Thu, 10 Nov 2005 10:18:08 GMT

Can I check the content of an DLT tape with
tar -t, no matter what kind of backupprogram have done the backup to the DLT-tape in HP-UX?

Re: Question about to show the content of an DLT-tape?

Pete Randall — Thu, 10 Nov 2005 10:23:48 GMT

Sure, you can run tar -t against any type of tape, produced by any type of backup program. However, if you want meaningful results, only expect to get them from tapes produced by tar.

Pete

Re: Question about to show the content of an DLT-tape?

Raj D. — Thu, 10 Nov 2005 10:27:38 GMT

Ignite backup tapes cannot be viewd with tar , unless you do Forward space count files (fsf) to 1 with mt.

hth,
Raj

Re: Question about to show the content of an DLT-tape?

Robert-Jan Goossens — Thu, 10 Nov 2005 10:30:37 GMT

Try dd'ing a part of the file from tape to disk and run the file command.

# dd if=/dev/rmt/Xm of=/tmp/foo =count=10
# file /tmp/foo

Robert-Jan

Re: Question about to show the content of an DLT-tape?

TwoProc — Thu, 10 Nov 2005 10:34:13 GMT

If the goal is to "look" at what is on the tape,

you could "dd" it.

dd if=/dev/rmt/0m
(results would come to the screen which could mess up your terminal)

or

dd if=/dev/rmt/0m of=/somedir/somefilename

You can also:

strings -a /dev/rmt/0m

or

cat /dev/rmt/0m

Re: Question about to show the content of an DLT-tape?

A. Clay Stephenson — Thu, 10 Nov 2005 10:38:24 GMT

No. Tar will only understand tar format tapes or files. In general when trying to determine the type of backup used to create a tape, the best approach is to extract the header or some portion of the header and examine it with a utilitity like od or xd. Often there are "magic numbers" (an actual technical term) that identify the type of backup and often one can simply recogize the type of backup by being familiar with the various formats.

Try something like this:

dd if=/dev/rmt/1m bs=1k count=1 | od -v -Ad -tao

This will print the first 1k chars of your tape in a meaningful format. If you don't recognize anything yourself then redirect the output to a file and post that. Someone will probably recognize what you have.

Re: Question about to show the content of an DLT-tape?

Andrew Rutter — Thu, 10 Nov 2005 10:46:49 GMT

hi,

rewind the tape first with
#mt -f /dev/rmt/xmn rew

the read the contents with tar

#tar tvf /dev/rmt/xmn

dump it to the screen or redirect it to a file as required.

if its an ignite backup tape then move the tape forward first before reading
#mt -f /dev/rmt/xmn rew
#mt -f /dev/rmt/xmn fsf1
#tar tvf /dev/rmt/xmn

Andy

Re: Question about to show the content of an DLT-tape?

ekke2 — Fri, 11 Nov 2005 01:50:16 GMT

With this
# dd if=/dev/rmt/0m bs=1k count=1 | od -v -Ad -tao
I got following result
dd read error: I/O error
0+0 records in
0+0 records out
0000000
#

Can someone tell me what this means?

Re: Question about to show the content of an DLT-tape?

Stephen Keane — Fri, 11 Nov 2005 05:03:38 GMT

It means either (a) the tape is positioned beyond the end of any data (in which case rewind the tape) or (b) there is no data on the tape.

Re: Question about to show the content of an DLT-tape?

Stephen Keane — Fri, 11 Nov 2005 05:04:48 GMT

Just as a matter of interest what does

# mt -f /dev/rmt/0m status

give you?

Re: Question about to show the content of an DLT-tape?

ekke2 — Fri, 11 Nov 2005 05:52:46 GMT

I got the following message.
# mt -f /dev/rmt/0m status
Drive: QUANTUM DLT8000
Format:
Status: [41118985] BOT online compression immediate-report-mode
File: 0
Block: 0
#

Re: Question about to show the content of an DLT-tape?

Stephen Keane — Fri, 11 Nov 2005 08:18:40 GMT

Well the tape is rewound (BOT) so that seems to indicate no data on the tape?

You could try

# dd if=/dev/rmt/0m of=/tmp/ekke count=10

(i.e. no block size)

Re: Question about to show the content of an DLT-tape?

ekke2 — Fri, 11 Nov 2005 08:31:58 GMT

I got the following info
dd read error: I/O error
0+0 records in
0+0 records out

with
dd if=/dev/rmt/0m of=/tmp/ekke count=10

Re: Question about to show the content of an DLT-tape?

Andrew Rutter — Fri, 11 Nov 2005 08:41:36 GMT

hi,

what output do you get if you try and read the tape like i suggested earlier

the read the contents with tar

#tar tvf /dev/rmt/Xmn

where X = your device file number

if you think the drive may have problems then try and do a test in cstm

Andy

Re: Question about to show the content of an DLT-tape?

ekke2 — Fri, 11 Nov 2005 08:52:25 GMT

The drive works fine.

With
tar tvf /dev/rmt/0mn
I get following message
Tar: tape read error

Re: Question about to show the content of an DLT-tape?

A. Clay Stephenson — Fri, 11 Nov 2005 11:18:34 GMT

There seems to be a logical disconnect here:
The drive works fine.

With
tar tvf /dev/rmt/0mn
I get following message
Tar: tape read error

By any chance, are you trying to read a tape that was recorded on an SDLT drive?

Are you able to create and read back a tar image on this drive? The fact that dd can't read from the tape strongly suggests either a hardware problem or bad/blank media.

Re: Question about to show the content of an DLT-tape?

Andrew Rutter — Fri, 11 Nov 2005 11:28:42 GMT

hi,

try a simple tar backup of /etc or something similar
then rewind the tape and try and read it

if this works it looks like bad media, if it fails a bad drive

Andy

Re: Question about to show the content of an DLT-tape?

V. Nyga — Fri, 11 Nov 2005 12:39:23 GMT

Hi,

when tar doesn't work, then you can try to read with SAM. In the backup/recovery area you have the option to list the content of a backup tape (could be the same like fbackup).
Else you can try to boot a client workstation with this tape.

Only some thoughts
Volkmar

Re: Question about to show the content of an DLT-tape?

ekke2 — Sun, 13 Nov 2005 06:34:01 GMT

Ok!
I have another question, does anyone know what Compress and Density Override mean on the DLT-station?

Should some of these leds be on when are
backing files?

Re: Question about to show the content of an DLT-tape?

A. Clay Stephenson — Mon, 14 Nov 2005 00:20:49 GMT

The "Density Override" LED inddicates that you have manually selected a density. It doesn't matter what density you choose for backing up although obviously the higher density will use less media. It does matter that the density used to read the medium matches that used when the medium was written. Normally for reading backups, the density override is not enabled and the drive will automaticaly adjust itself to match the recording density.