1. CUPS Print Services

2. What is CUPS?
CUPS (formerly an acronym for Common Unix Printing System, but now with no official expansion) is a modular printing system for Unix-like computer operating systems which allows a computer to act as a print server.
A computer running CUPS is a host that can accept print jobs from client computers, process them, and send them to the appropriate printer.

3. Cont..
CUPS uses the Internet Printing Protocol (IPP) as the basis for managing print jobs and queues.
Design Overview

4. Cont..
CUPS is designed around a central print scheduling process that dispatches print jobs, processes administrative commands, provides printer status information to local and remote programs, and informs users as needed
Scheduler
Configuration Files
CUPS API
Berkeley and System V Commands
Filters
CUPS Imaging
Backends

5. Cont.. Scheduler: Handles Http request
Acts as a web server for documentation, status monitoring, and administration.
Manages a list of available printers on the LAN
Dispatches print jobs as needed using the appropriate filters and backends

6. Cont.. Configuration Files: The configuration files consist of:
The HTTP server configuration file.
Printer and class definition files.
MIME type and conversion rule files.
PostScript Printer Description ("PPD") files.
Http Server Configuration File:
defines all of the access control properties for the server.
Printer And Class Definition Files:
list the available printer queues and classes.
(jobs done in round robin fashion).

7. Cont.. MIME type files: list the supported MIME types PPD Files:
describe the capabilities of all printers. There is one PPD file for each printer.
CUPS API:
functions for queuing print jobs, getting printer information, accessing resources via HTTP and IPP, and manipulating PPD files.
Berkeley and System V Commands:
command-line interfaces for submitting jobs and checking the printer status. The lpstat and lpc status commands are used.

8. Cont..
Filters:
A filter program reads from the standard input or from a file if a filename is supplied.
All output is sent to the standard output.
CUPS IMAGING:
The CUPS Imaging library provides functions for managing large images, doing colorspace conversion and color management, scaling images for printing.

9. Installation Command: sudo apt-get install cups
Configuration File in location
/etc/cups/cupsd.conf
Prior to editing the configuration file, you should make a copy of the original file and protect it from writing.
sudo cp /etc/cups/cupsd.conf /etc/cups/cupsd.conf.original
sudo chmod a-w /etc/cups/cupsd.conf.original

10. Cont.. Server Admin: Listen:
configure the address of the designated administrator in config file.
Listen:
In order to instruct the CUPS server to listen on an actual network adapter's IP address, you must specify either a hostname, the IP address
We can assign the systems that which the server to listen using LISTEN command.
Eg.,
Listen : # existing loopback ListenListen Listen /var/run/cups/cups.sock # existing socket Listen
Listen : # Listen on the LAN interface, Port 631 (IPP)