CentOS - Sep 2005 - scsi tape drive problems

I am experimenting with a scsi2 HP SureStore DAT24 attached as an 
external device to an Intel P4 system.  I am attempting to create a 
raw disk image of a dds2 tape made on a non linux system.

My immediate problem is that I am trying to terminate a dd process 
and having no luck.  dd was invoked thus:

dd if=/dev/nst1 of=/tmp/disk.dds2.img bs=512 & pid=$!

a ps reveals this:

ps
  PID TTY          TIME CMD
 1936 pts/0    00:00:00 bash
 2034 pts/0    00:00:15 dd
 2093 pts/0    00:00:00 ps

a call to kill has no apparent effect:

kill -s SIGKILL 2034
ps
  PID TTY          TIME CMD
 1936 pts/0    00:00:00 bash
 2034 pts/0    00:00:18 dd
 2100 pts/0    00:00:00 ps

and calls to mt show this:

mt -f /dev/nst1 status
/dev/nst1: Device or resource busy


Short of a reboot, how do I get control of the tape drive back?  
(once I get the drive back I will have a lot of other questions 
regarding dd.)

Regards,
Jim

--   .
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James B. Byrne                Harte & Lyne Limited
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On Mon, 26 Sep 2005 at 4:17pm, James B. Byrne wrote
> I am experimenting with a scsi2 HP SureStore DAT24 attached as an
> external device to an Intel P4 system.  I am attempting to create a
> raw disk image of a dds2 tape made on a non linux system.
>
> My immediate problem is that I am trying to terminate a dd process
> and having no luck.  dd was invoked thus:
>
> dd if=/dev/nst1 of=/tmp/disk.dds2.img bs=512 & pid=$!
>
> a ps reveals this:
>
> ps
>  PID TTY          TIME CMD
> 1936 pts/0    00:00:00 bash
> 2034 pts/0    00:00:15 dd
> 2093 pts/0    00:00:00 ps
That dd command will continue until it hits an EOF (I believe -- maybe 
EOD).  Until then, it'll be in the 'D' state (waiting for I/O), and 
therefore unkillable.  You'll just have to wait it out (or, as you 
conjectured, reboot).  Is the tape drive reading (and, correspondingly, 
the disk writing)?

-- 
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University

James B. Byrne wrote:
> I am experimenting with a scsi2 HP SureStore DAT24 attached as an 
> external device to an Intel P4 system.  I am attempting to create a 
> raw disk image of a dds2 tape made on a non linux system.
> 
> My immediate problem is that I am trying to terminate a dd process 
> and having no luck.  dd was invoked thus:
> 
> dd if=/dev/nst1 of=/tmp/disk.dds2.img bs=512 & pid=$!
... snip ...
> Short of a reboot, how do I get control of the tape drive back?  
> (once I get the drive back I will have a lot of other questions 
> regarding dd.)
I assume that your reason for an early termination is that you
want to look at some of the data w/o taking time for it all to be
read in.  If that is the case, just use the *count* arg to dd.

Sooner or later, you will need to read it all in so just do it now,

"nice" the "dd" process down and continue to use your
system.

Hope this helps,
Ray