Andrew Hudson - Fedora™ Unleashed, 2008 edition

► http://f-spot.org— Home page of the F-Spot project.

► http://www.linuxformat.co.uk— Website of Linux Format, home of a long-running GIMP tutorial by Michael J Hammel.

► http://www.exif.org— More information on EXIF and how it is used in digital cameras.

► http://www.sane-project.org— Home page of the SANE (Scanner Access Now Easy) project.

► http://www.imagemagick.org— Home page for ImageMagick.

► http://www.codeweavers.com— Home of the popular crossover office; required if you want to try to run Photoshop under Linux.

► http://gimp.net/tutorials/— Official tutorials for The GIMP.

From the word go , Fedora provides support for a huge range of printers from many different manufacturers. This chapter looks at how to get your printer connected and talking to Fedora, as well as at the software that Fedora uses to manage printers and print jobs.

In keeping with most of the other Linux distributions, Fedora uses CUPS ( Common Unix Printing System ) to handle printers. Other systems are supported, such as LPRng, but you do not have access to some of the graphical management tools from within Fedora.

CUPS supports the Internet Printing Protocol, known as IPP , and offers a number of unique features, such as network printer directory (printer browsing) services, support for encryption, and support for PostScript Printer Description ( .ppd) files.

According to the Internet Engineering Task Force ( IETF ), IPP grew out of a 1996 proposal by Novell to create a printing protocol for use over the Internet. Since then, the system has been developed and has matured into a stable print system for use on a variety of Linux and Unix-like operating platforms.

Fedora's print filter system is the main engine that enables the printing of many types of documents. The heart of that engine is the GNU GPL version of Aladdin's Ghostscript interpreter, the gsclient. The system administrator's printer configuration tool is the system-config-printerclient.

Fedora's print system can be used to print to local (attached) or remote (network) printers. If you use a local printer, it is represented by a printer device, such as /dev/ip0or /dev/usb/ip0(if you have a USB printer). Local and remote printers use print queues defined in your system's printer capabilities database, /etc/printcap. A document being printed is known as a print job, and you can view and control your list, or queue, of current print jobs in the spool directory, which is /var/spool/cups. Note that you may control only your print jobs; only the root operator can control print jobs of any user on the system.

To add a printer to your system, you use the system-config-printer client to create, configure, and save the printer's definition. The client saves the definition as an entry in your system's printer capabilities database, /etc/printcap. Each definition contains a text field with the name of the printer, its host, and name of the print queue. Printed documents are spooled to the /var/spool/cupsdirectory. A sample printcapdefinition might look like the following:

# This file was automatically generated by cupsd(8) from the

# /etc/cups/printers.conf file. All changes to this file

# will be lost.

Officejet|Officejet Pro K5400:rm=teletran.hudson.com:rp=Officejet:

CUPS maintains its own database of defined printers under the /etc/cupsdirectory in a file named printers.conf. For example, an associated printer defined in /etc/printcappreviously might have the following entry in /etc/cups/printers.conf:

# Printer configuration file for CUPS v1.3.3

# Written by cupsd on 2007-10-28 19:30

Info Officejet Pro K5400 Location Office

DeviceURI socket://192.168.0.100:9100

State Idle

StateTime 1193599791

Accepting Yes

Shared Yes

JobSheets none none

QuotaPeriod 0

PageLimit 0

KLimit 0

OpPolicy default ErrorPolicy stop-printer

This example shows the definition for the printer named lp, along with its associated device, description, state, and other information. The various possible fields and entries in this file are documented in the printer.confman page.

CUPS uses a print server (daemon) named cupsd,also called a scheduler in the CUPS documentation. The server can be controlled, like other Fedora services, by the servicecommand or system-config-services client. How the server works on a system is determined by settings in its configuration file, cupsd.conf, found under the /etc/cupsdirectory. CUPS executables are found under the /usr/lib/cupsdirectory.

The cupsd.confman page documents more than 80 different settings for the server, which you can configure to match your system, network, or printing environment. Default CUPS-related files and directories are stored under the /usr/share/cupsdirectory. Logging can be set to seven different levels, with information about access and errors stored in log files under the /var/log/cupsdirectory.

Resource requirements can be tailored through other settings, such as MaxCopiesto set the maximum number of copies of a print job by a user, MaxJobsto set a limit on the number of active print jobs, and MaxJobsPerUserto set a limit on the number of active jobs per user. The RIPCachesetting (8MB by default) controls the amount of memory used for graphics cache during printing.

For example, if you want to limit printing to 20 copies of a document or page at a time and only 10 simultaneous print jobs per user, use settings such as the following:

MaxCopies 20

MaxJobsPerUser 10

Do not forget to restart the CUPS server after making any changes to its configuration file. Changes are activated only when the service is restarted (when the daemon rereads its configuration file). See the "GUI-Based Printer Configuration Quick Start" section later in this chapter.

Because CUPS does not use the traditional Berkeley-style print spooling system, lpd,you can change the name of the printer capabilities database from the default /etc/printcap. Encryption can be used for printing, with secure access behavior determined by settings in /etc/cups/client.conf. Network access settings include port, connection, IP address, domains, and limits to the number and size of client requests.

Your task as a system administrator (or root operator of your workstation) is to properly define local or remote printers and to ensure that printing services are enabled and running properly. Fortunately, Fedora includes a graphical print service configuration tool that makes this job easy. You should use these tools to configure printing, as you learn in this section of the chapter. But first, take a moment to read through a quick overview of the configuration process.

Do not manually edit your /etc/printcap. Any changes will be lost when the printing service is restarted or if your system is rebooted. If you need to create customized printer entries, save the entries in /etc/printcap.localand then restart the printing service.