Tips And Tricks III

Networked printing

In small networks, as they are very common at home or in a small office, there is only one machine, the server, which connects to the Internet, and each client uses this server as the gateway to connect. Often the printer is also connected to this machine. And because this machine has two Ethernet addresses, one for the Ethernet card connecting to the client(s) and one (usually dynamic) for the device connecting to the Internet, there are problems with the automatic broadcasting of printer information to the clients by CUPS. Here are step-by-step instructions to set up such a network so that both printer and Internet access work correctly. I assume that you have already set up Internet access on the server.

Note: All names and IP addresses in this example can be replaced, but be careful that you do not choose any unsuitable IP address. The address for the server should start with "192.168." (local network) and it should not conflict with the IP address of the Internet connection ( at least one of the first three numbers of the IP should differ from the IP of the Internet access).

First make sure that the server has a well-defined host name for the local network.

For this, install server and clients as follows:

On the server (the two steps can be done in any order):

• Start 'linuxconf', choose "Networking" and then "Host name and IP network devices".
  Click on the tab for the network interface of your local network. Fill in the "Primary name + domain" field with "server.localdomain". Do not keep the name "localhost" or "localhost.localdomain" here. Set the IP address to "192.168.0.1"

• Set up "Internet Connection sharing" with the appropriate subprogram of 'DrakConf'. If you access the Internet via a second network card, choose the one for the local network.

Run 'linuxconf' on all clients and set up automatic network configuration via DHCP. For this choose "Networking" and then "Host name and IP network devices".
Click on the tab for the network board and mark the "DHCP" field.

Add an entry for your server name to '/etc/hosts'. For example add the line: 192.168.0.1 server.localdomain server. Make sure that you enter the correct name and IP address of the local network interface of your server.

Reboot the server and the clients to make sure that all network settings are used by the machines.

On the server add the lines

ServerName server
BrowseAddress 192.168.0.255

to '/etc/cups/cupsd.conf' and restart the CUPS daemon with

service cups restart

Now you have an automatic broadcasting for your local network and all the clients see your printers and can print on them.

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For high-demand printing you can set up printer clusters, consisting of several identical printers located in the same room. Jobs are sent to one queue and get distributed among all currently available printers.

To set up such a cluster, define one queue for every printer and unite all these queues in a class of printers. Choose "Printer"/"Add" in the menu of 'Kups' and then "Class of printers" in the "Backend selector" screen. On the next screen click on the first printer of the cluster, then on ">", on the second printer, on ">", and so on. Finally click on "Next", name the class and you are set. Classes can also be defined via the web interface: go to the "Manage Printer Classes" page, choose "Add class", enter the name of the class and then select the printers of your cluster.
On the command line you enter:

lpadmin -p <printer1> -c <class&gt
lpadmin -p <printer2> -c <class&gt
...

Now send the printing jobs to the class and they will be printed on the next free printer of the class.

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Redundant queues for one printer

If you have a very important Ethernet-connected printer, you can make it independent of one individual host by setting up redundant queues on different machines for it.

Enable the "Implicit Classes" facility on every machine in your network. This is a so-called implicit class: several queues with identical names exist on different machines in your network. The class will have the name of these queues and a job sent to this class will be put into the first queue responding. To turn on this feature, put the line

ImplicitClasses On

into your '/etc/cups/cupsd.conf' and restart the CUPS daemon with

service cups restart

Or, if you prefer to use 'kupsdconf', turn on "Implicit Classes" under "Browsing".

Now set up eponymous queues for your Ethernet-connected printer on different machines. The printer will appear with a [printer]@[server] queue for every server and with one additional [printer] queue. This additional queue is the implicit class and when you print to it, the job is forwarded to the first server which answers. It does not matter when some servers are down, when at least one server works, it will print.

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CUPS and LPD on the same machine

Under Linux Mandrake it is even possible to have CUPS and LPD running on the same machine. This can be useful if you want to have the CUPS printers on the network available, but there is also a local printer with a driver for which there is no PPD file (all free drivers should have a PPD available on linuxprinting.org, if you find a free driver which is not mentioned there, please tell me).
If you just want to have one of your CUPS printers available on a machine running only LPD, use the CUPS-LPD mini-daemon.

To get LPD running you should at first turn off the automatic generation of an '/etc/printcap' file by CUPS: comment out the Printcap /etc/printcap line in '/etc/cups/cupsdconf' ('kupsdconf': Mark "Default" for "Printcap file" in "Server"/"Misc") and restart the CUPS daemon with service cups restart.

Now install LPD and its printing filters with

urpmi lpr rhs-printfilters

and start the LPD daemon with

chkconfig --add lpd
service lpd start

The commands lpr, lpq, lprm, and lpc are the same under both printing systems, to access the LPD versions of them use lpr-lpd, lpq-lpd, lprm-lpd, and lpc-lpd. Read the appropriate 'man' pages for more information.

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CUPS on Linux Mandrake 7.1

If you still have a machine with Mandrake 7.1 and you want to use CUPS, you can install the CUPS packages of Linux Mandrake 7.2. Proceed like this:

Stop LPD:

/etc/rc.d/init.d/lpd stop

and backup your '/etc/printcap' file. Remove the "lpr" package and related packages:

rpm -e --nodeps lpr
rpm -e --nodeps rhs-printfilters
...

Download these RPM packages from a download site for Linux Mandrake 7.2 (or copy them from the first CD of Linux Mandrake 7.2):

• cups
• cups-drivers
• ghostscript
• ghostscript-module-X
• ghostscript-module-SVGALIB
• ghostscript-utils
• xpp
• qtcups
• samba
• samba-common
• samba-client

Install the "cups" package:

rpm -Uvh --nodeps cups-1.1.4*.rpm

Set up links for easier access to the CUPS shell commands:

cd /usr/bin
ln -s lpr-cups lpr
ln -s lpq-cups lpq
ln -s lprm-cups lprm
cd /usr/sbin
ln -s lpc-cups lpc

Now install all the other downloaded packages with

rpm -Uvh [package file name]

Start CUPS with

chkconfig --add cups
service cups start

Now you can configure and use CUPS as described in this article. Note that 'PrinterDrake' and 'Kups' are not available. Use the web interface of CUPS instead.

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