Introduction

LPD and LPR

Traditionally, UNIX had two printing systems: the BSD Line Printer Daemon (LPD) and the System V Line Printer system (LPR). Linux adopted those systems at first, and both UNIX and Linux have seen modifications to and replacements for these systems. Today CUPS is the default printing system under Red Hat Linux.

CUPS

CUPS (Common UNIX Printing System) is a cross-platform print server built around IPP (Internet Printing Protocol), which is itself based on HTTP. CUPS provides a number of printer drivers and can print several different types of files, including PostScript. Because it is built on IPP and written to be portable, CUPS runs under many operating systems, including Linux and Windows. Other UNIX variants, including Mac OS X, use CUPS, and recent versions of Windows include the ability to print to IPP printers, making CUPS an ideal solution for printing in a heterogeneous environment. CUPS provides System V and BSD command line interfaces and, in addition to IPP, supports LPD/LPR, HTTP, SMB, and JetDirect (socket) protocols, among others.

IPP

The IPP project (www.pwg.org/ipp) began in 1996, when Novell and several other companies decided to design a protocol for printing over the Internet. The IPP enables users to

• Determine the capabilities of a printer.

• Submit jobs to a printer.

• Determine the status of a printer.

• Determine the status of a print job.

• Cancel a print job.

IPP is a client/server protocol in which the server side can be a print server or a network-capable stand-alone printer.

Printers and queues

On a modern computing system, when you "send a job to the printer," you actually add the job to the list of jobs waiting their turn to be printed on a printer. The list is called a print queue or simply a queue. The phrase configuring (or setting up) a printer is often used to mean configuring a (print) queue. This chapter uses these phrases interchangeably.

Prerequisites

Install the following packages:

• cups

• system-config-printer (optional)

• kdebase (optional, provides kprinter)

Run chkconfig to cause CUPS (the cupsd daemon) to start when the system goes into multiuser mode:

# /sbin/chkconfig cups on

Start CUPS:

# /etc/rc.d/init.d/cups start

To use the Web interface to CUPS, you need an X server and a Web browser.

More Information

Local

CUPS Documentation With the CUPS Web interface up (page 512), point a local browser at localhost:631/documentation.html.

Web

www.linuxprinting.org Information on printers and printing under Linux; hosts a support database with details about many printers, including notes and driver information; also forums, articles, and a HOWTO document on printing.

CUPS home page www.cups.org

IPP information www.pwg.org/ipp

HOWTO

SMB HOWTO has a section titled "Sharing a Windows Printer with Linux Machines."

Notes

SELinux

When SELinux is set to use a targeted policy, CUPS is protected by SELinux. You can disable this protection if necessary. For more information refer to "Setting the Targeted Policy with system-config-securitylevel" on page 402.