media changer / mc error message

[Lonny Balderston]

HPUX command "mc", most variations, get error message, example:
# mc -r MIDS
ERROR: No such file or directory
What's up with this? Thanks.

[Ashwani Kashyap · Accepted solution]

You got to specify the device file first whic "mc" has to act upon whith the -p option .

mc is used for controlling the robotics of a tape library . There is a special device file for the robotics usually created in /dev/rac , if you use and schgr driver or you create on of your own using mknod if you are using an sctl driver .

That device file is specified with the mc command with the -p option .

[JDL_2]

As said, mc is used to control the robotic arm in tape libraries. This may mean that you do not have the special device name in the /dev/rac directory. To do this, install it with "insf -C autoch". If not install everything that your system that it doesn't have by "insf -e". Consult the insf man pages for more details.

JDL

[Michael Tully]

Hi,

If you have a piece of equipment that requires a robotic device setup like a tape library, you need to make sure that you have the appropriate driver for your equipment in your kernel. Once this is done a correct device still needs to be created to drive the robot. Without it you cannot use the 'mc' command at all.
Use the attached document as a guide.

HTH
Michael

[Bill Hassell]

Unless you use -p to specify the device file used to address the robotic arm and controller, the valu of the environment variable $LIBRARY is used. NOTE: depending on the driver used, the major number may be dynamic (different) than the examples shown. Dynamic drivers numbers are assigned when the driver is added to the kernel.

[Lonny Balderston]

Yes, the "-p" gets me past the error message.

I stumbled into the "fix", but now I want to know how this works.

At the time of install, my FE created a device file /dev/scsi/3, and told me it was equivalent to /dev/rac/c0t0d0. I was able to use the mc command with no -p argument. On another of our company's machines, this had not been done, and hence the problem (need to specify the passthrough device file). So, what is the tape unit doing with /dev/scsi/3? And, I don't see any environmental variable $LIBRARY on either machine.

Thanks to all for your help!

[Michael Tully]

I agree with Bill. There must be somewhere a variable which defines the robot device (/dev/scsi/3). In my experience this is unusal, however not unheard of.
Once the kernel has been updated, the device to drive the robot can be easily defined using the document that I attached earlier. If your changing from one system to another to drive the robot, you may also need to reboot your tape library and MUX if you have one, particularly if your attached through a fibre switch.

If you cannot get the robot going, post a copy of your ioscan (assuming you already have the kernel drivers loaded,) and we can help with the device creation.

Regards
Michael

[Lonny Balderston]

Michael, great info in the doc, but it's far beyond the scope of my question. The initial problem was only that the passthrough device file needed to be named (mc -p devfile). Now I'm wondering why creating /dev/scsi/3 allows one to leave the -p param off the mc command. Again, thanks for the info!

[Dietmar Konermann]

IMHO the name /dev/scsi/3 does not follow _any_ standard naming convention. Many people use self-made names for their pass-trough devices. But you cannot leave -p option unless the LIBRARY variable is defined.

BTW, the correct naming would be /dev/rscsi/cXtYdZ with X/Y/Z matching ext_bus/target/lun.

Best regards...
Dietmar.