[cups.general] usb printer assignement

[Johannes Meixner]

Hello,

On Aug 11 20:22 sandy basickes wrote (shortened):
>   We then added the 3 usb printers:
>        ML421 Oki Data (fed with double sheet paper) ( default)
>        ML421 Oki Data (fed with single sheet paper)
>        Toshiba B-SA4T
>   In cups, these were named lp, p1 and tecb respectively.
>   The first two Oki printers are the same make and model.
>
>   When the system is booted with all printers powered, the
>   printers are assigned randomly to /dev/usb/lp0,
>   /dev/usb/lp1 and /dev/usb/lp2.  When we print
>   to lp, cups sends the data to whichever printer was randomly
>   assigned to /dev/usb/lp0 at startup.

I wonder how exactly you added the 3 USB printers.

To set up a print queue in compliance how CUPS works,
you could do the following via CUPS commandline tools:

1.
Retrieve autodetected printers and their correct matching
DeviceURIs from the cupsd: Run as root: "lpinfo -l -v"

2.
Retrieve available printer driver descriptions from the
cupsd: Run as root: "lpinfo -l -m"

3.
Select a printer/DeviceURI from the "lpinfo -l -v" list
and a printer driver from the "lpinfo -l -m" list and
choose an arbitrary queue name.

4.
Set up the queue as root via
"lpadmin -p queue_name -v DeviceURI -m printer_driver -E"


If the CUPS backend "usb" could not distinguish your
two same Oki printers (e.g. because those printers do not
provide a serial number via USB), you would not be able
to set up two queues for them because you would not get
two different DeviceURIs for them.

But you did set up two queues for them and therefore
I wonder how you actualy did it.

Perhaps you (or whatever Debian setup tool) still uses the
meanwhile outdated traditional DeviceURIs for USB printers
like usb:/dev/usb/lp* instead of the new form like
usb://<make>/<model>?serial=<number>

For background information you may have a look at
http://en.opensuse.org/SDB:CUPS_in_a_Nutshell

If your two same Oki USB printers cannot be distinguished
at the USB, you can only connect one of them in a different way,
e.g. buy a printserver-box with ethernet and USB connectors
and access one Oki printer as network printer, in this case see
http://www.cups.org/documentation.php/doc-1.4/network.html


Kind Regards
Johannes Meixner
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