Tape Drives Don't Rewind with mt?

[Jeanine Kone]

I just got new Ultrium tape drives installed on my servers. I am having trouble getting all of my backup commands to work.

If I write to the tape using the /dev/rmt/0mn device and then use mt -f /dev/rmt/0m rewind to rewind the tape, I get error messages when I try to list the contents of the tape (it's like it did not actually rewind).

If I use the /dev/rmt/0m device when writing to the tape (and thus can skip the rewind), I can read the contents just fine. I unfortunately, need to use the no rewind device b/c I am writing new files to the tape every hour.

Any idea why the mt -f device rewind command does not work?

While I am at it, I am having trouble getting fbackup to use the device as well. I get an error that output file /dev/rmt/0m (or 0mn) is not a valid device file for backup. Any ideas?

[Vincenzo Restuccia]

Try mt -t /dev/rmt/0m rewind

[melvyn burnard]

Hmm,. a man mt shows no -f option, only the -t.

SO I guess you should try :
mt -t /dev/rmt/0m rew


as per the man page

[Jeanine Kone]

I am using HP-UNIX 11. My man page says
"mt [-f tapename] command [count]"
It shows the -t option as obsolete.

Jeanine

[James R. Ferguson]

Hi Jeanine:

# mt -t /dev/rmt/0m rew

...should rewind the tape on 10.x or 11.x.

The '-t' flag is considered obsolete as of 11.x. The preferred flag for 11.x is '-f'.

...JRF...

[A. Clay Stephenson]

Hi Jeanine:

I would check the minor device numbers of the device nodes to see if they are correct. Also,
you may have better success using the 'Berkeley' style device 0mnb

e.g. mt -f /dev/rmt/0mnb rew

[Jeanine Kone]

I have eight (four rew, for norew) possible device names for the one tape drive - how do I know which to use and what are the differences?

They are:
/dev/rmt/0m(n)
/dev/rmt/0m(n)b
/dev/rmt/c0t3d0BEST(n)
/dev/rmt/c0t3d0BEST(n)b

Thanks!

[A. Clay Stephenson]

Hi Jeanine,

If you compare the major and minor device numbers of the nodes you mentioned, you will find that they come in pairs, e.g.
/dev/rmt/0mnb
/dev/rmt/c0t3d0BESTnb

These are the Berkley-style (as opposed to the AT&T style tapemark conventions) no rewind devices are you can use either of them interchangably.

The major/minor device numbers are all that are important. The 0mnb is just a shorthand convention to make typing easier, the longer name is more descriptive (e.g. Controller 0, SCSI ID 3, LUN 0, BESTnb refer to the low-order bits of the minor device number and do thing like compression, rewind, tape marks, etc. In any event, you could call the node 'Dopey' and as long as you had the major/minor devive numbers the same, it would work just fine.


The mt(1) man page clearly states that only Berkeley style no-rewind devices should be used. For a good explanation of the device node conventions and minor device number assignments man mt(7).

Regards, Clay