topic Re: Problem tarring to a device on a remote system in Operating System - Linux

Problem tarring to a device on a remote system

Andrew Kaplan — Tue, 14 Dec 2010 22:16:54 GMT

Hi there --

I am trying to tar a directory on one system, to an LTO-4 device attached on a remote system but am unable to do so. The command syntax that I am using on the first system is the following:

tar -cvf :/dev/rmt/6mn . --rsh-command=/usr/bin/ssh

The error message that I am getting is the following:

Cannot open /dev/rmt/6mn input/output error /usr/bin/rmt not found.

I checked the remote system, and the rmt file is located in the /usr/local/bin and /usr/sbin directories. At first I thought that was the problem, but then I tried the same command on the first computer to tar to an attached device on another system similar to the latter one, and the tar went by without a hitch. When I checked for the location of rmt on that system, it too was located in the /usr/sbin/ directory.

The system running tar is a Fedora Core 2 system, while that with the attached tape device is an HP-UX 11.11 server. I confirmed the hardware file for the tape device, and due to the configuration of the server, it is necessary to use the 6mn as opposed to the 6m hardware file.

What is causing this issue to occur, and how can it be corrected?

Re: Problem tarring to a device on a remote system

Steven Schweda — Wed, 15 Dec 2010 04:26:40 GMT

> What is causing this issue [...]

Is that anything like a _problem_?

I know nothing, but ...

Have you read the GNU "tar" instructions
related to "Choosing and Naming Archive
Files" and using a "Remote Tape Server"?

http://www.gnu.org/software/tar/manual/

> [...] another system similar [...]

Define "similar". As usual, actual output
from actual commands, like, say, "uname -a"
can be more helpful than vague descriptions
or interpretations.

As I understand this stuff, when you tell GNU
"tar" to talk to a remote device, you're
really telling it to use "rsh"/"remsh" (or,
if requested, "ssh") to open a session on the
remote system, and to run a remote-tape
server ("rmt") program there, which will do
the actual I/O with the remote tape device.

> [...] /usr/bin/rmt not found.

Apparently, it's not finding this "rmt"
program where it's looking for it. If GNU
"tar" doesn't have a convenient option to let
you specify some other path to the remote
"rmt" program, then you may need to create a
link to (or a copy of) the right file in the
expected place.

> I confirmed the hardware file for the tape
> device, [...]

Nice, but without an appropriate "rmt" where
it's expected, all the hardware support in
the world won't get GNU "tar" in touch with a
remote tape drive.

Note that I haven't looked to see if HP-UX
11.11 comes with an appropriate "rmt"
program, or if you should be using the one
which is supplied with GNU "tar", and, of
course, with my weak psychic powers, I also
have no idea if you have GNU "tar" (with its
"rmt" program) installed on the HP-UX system
(and, if so, where).

Re: Problem tarring to a device on a remote system

Andrew Kaplan — Wed, 15 Dec 2010 22:00:17 GMT

I decided to solve the problem using a different strategy:

The system that has the LTO-4 drive attached to it was configured to mount the directory subject to the tar backup as an NFS mount. Once that was done, the tar command was run with the data going to the locally attached drive.

Re: Problem tarring to a device on a remote system

Steven Schweda — Wed, 15 Dec 2010 23:43:08 GMT

> I decided to solve the problem using a
> different strategy:
> [...]

If you had asked how to get a "tar" back-up
of a GNU/Linux file system onto a tape drive
which was connected to an HP-UX system, then
you might have gotten advice like, "Use
NFS?". But that's not what you asked.

Note that an old HP-UX "tar" program and/or
old HP-UX NFS client software may impose
limits (file size, file path name length,
...) which would not be encountered using GNU
"tar" (somewhere).

Re: Problem tarring to a device on a remote system

Andrew Kaplan — Thu, 16 Dec 2010 00:53:24 GMT

...

Re: Problem tarring to a device on a remote system

Steven Schweda — Thu, 16 Dec 2010 02:52:20 GMT

You're welcome.