CUPS - The Common Unix Printing System

The CUPS print server is a popular print service that supports LPD, LPR, IPP, Samba and Jetdirect style printers. CUPS is the default print server on most versions of Linux, including Redhat, Centos, Fedora, Debian and Ubuntu. CUPS supports a variety of print filters, in the form of PPD and interface scripts, as well as a number of different backends for different printing protocols. CUPS is developed and supported by Apple Inc, and is also the print server for the Apple OS X operating system.

Howtos, Examples and Observations

CUPS command line examples - Common CUPS Directives

CUPS troubleshooting on the Linux command line - CUPS CLI Troubleshooting

CUPS lpr: Unauthorized Message - lpr: Unauthorized