Testing the Printing Class...
Adding the "New Class" in the Unix printing environment means a
capability to create a clustered printers using one single alias name
for the group of the printers. This means that you may create one class
and assign into it many printers and set the class to be your default
printer instead using only one single printer. If you have e.g. two
similar printers in one place at work, you can create a class for those
two printers to be able to load balance your print jobs between those
two printers. This also helps then when the other printer fails, the
printing queue of the class redirects all the new requests to the
remaining printer.
An easy and funny 10-steps-back-and-forth-way to test the printing classes on
the Linux with the "dummy" printers described here below:
Open two different terminal windows and type "tty" on both of them. By default
the values are somewhat: "/dev/pts/0" and "/dev/pts/1" depending on how many
terminal sessions you had open prior. Create couple of dummy printers using the
command line as seen here below. First, if you have the CUPS in use, you have
to add into the /etc/cups/cupsd.conf file the URI directive "FileDevice Yes"
without quotation marks to be able to use the lpadmin command. After adding the
line, you have to restart the CUPS.
1. Add the "FileDevice Yes" directive to the last line of the file
$ sudo vi /etc/cups/cupsd.conf
2. Restart the CUPS service to make the new directive effect
$ sudo /etc/init.d/cups restart
3. Add two dummy printers to the system (remember to check the dummy pseudo
device addresses of the terminals opened earlier to be the
destination dummy printers).
$ sudo lpadmin -p test1 -v /dev/pts/0 -o nobanner -u allow:all
$ sudo lpadmin -p test2 -v /dev/pts/1 -o nobanner -u allow:all
4. Enable and accept the newly created devices and check that the devices are
accepting printing requests and being enabled
$ sudo cupsenable test1 test2
$ sudo accept test1 test2
$ sudo lpstat -t
5. If the dummy devices are being created correctly, you should be able to
print in to their dummy output devices terminal windows from the third terminal
window using the commands seen here below. In the example we are printing the
content of the ascii file /etc/passwd to them.
$ lp -d test1 /etc/passwd
$ lp -d test2 /etc/passwd
6. If you were able to print to the both of the dummy devices, then the
printing class can be created using the following commands (remember to check
what was your initial default printer and mark that information down before
moving on to be able to restore your preferred real printing environment back
later on)
$ sudo lpadmin -p test1 -c class1
$ sudo lpadmin -p test2 -c class1
7. Let's make the "class1" printing class the default printer for the system
that we are able to test the class in action.
$ sudo lpadmin -d class1
8. Now you can print and repeat the printing jobs as many as you like
and as fast as you can from the 3rd terminal window to this class1
printing class. Note, now that we made the class1 to be your default
printer, you don't have to use the -d destination option with the
command lp, to be able to print to the class1 directly.
$ lp /etc/passwd; lp /etc/passwd; lp /etc/passwd; lp
/etc/passwd; lp /etc/passwd
9. and notice that the system is now by default load balancing the print jobs
between these two dummy devices test1 and test2. The following set of commands
is for restoring the initial status of the system and removing these dummy
devices. T
$ sudo lpadmin -x class1
$ sudo lpadmin -x test1 test2
$ sudo lpadmin -d <initial printer>
10. Remove the last line directive entry from the file /etc/cupsd.conf we added
there earlier if it is bothering you and restart the CUPS.
$ sudo vi /etc/cups/cupsd.conf
$ sudo /etc/init.d/cups restart
These instructions are valid for the real case creations just by
replacing the dummy devices with the real ones. These instructions are
valid also for the GUI creation with the GUI program Printing, which by
the way does have an authorization bug on the Ubuntu, so you should
launch the program from the command line with the command: "sudo python
/usr/share/system-config-printer/system-config-printer.py" if you would
like to use x program instead. Due to my nature of CLI lower, I don't
bother to explain how to do the thing in the x environment... :-)
--
printer configuration largely undocumented
https://bugs.launchpad.net/bugs/208240
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