Red Hat Fedora Linux 3 Bible

CUPS has become the standard for printing from Linux and other UNIX-like operating systems. Instead of being based on older, text-based line printing technology, CUPS was designed to meet today's needs for standardized printer definitions and sharing on IP-based networks (as most computer networks are today). Here are some features of CUPS:

• IPP — At its heart, CUPS is based on the Internet Printing Protocol (www.pwg.org/ipp), a standard that was created to simplify how printers can be shared over IP networks. In the IPP model, printer servers and clients who want to print can exchange information about the model and features of a printer using HTTP (that is, Web content) protocol. A server can also broadcast the availability of a printer, so a printing client can easily find a list of locally available printers.

• Drivers — CUPS also standardized how printer drivers are created. The idea was to have a common format that could be used by printer manufacturers that could work across all different types of UNIX systems. That way, a manufacturer only had to create the driver once to work for Linux, Mac OS X, and a variety of UNIX derivatives.

• Printer classes — Using printer classes, you can create multiple print server entries that point to the same printer or one print server entry that points to multiple printers. In the first case, multiple entries could each allow different options (such as pointing to a particular paper tray or printing with certain character sizes or margins). In the second case, you could have a pool of printers so that printing is distributed. This would decrease the occurrence of congested print jobs, caused by a malfunctioning printer or a printer that is dealing with very large documents.

• UNIX print commands — To integrate into Linux and other UNIX environments, CUPS offers versions of standard commands for printing and managing printers that have been traditionally offered with UNIX systems.

The Printer configuration window (system-config-printer command) lets you configure printers that use the CUPS facility. However, CUPS also offers a Web-based interface for adding and managing printers. Configuration files for CUPS are contained in the /etc/cups directory. In particular, you might be interested in the cupsd.conf file (which identifies permission, authentication, and other information for the printer daemon) and printers.conf (which identifies addresses and options for configured printers).