Line Printer Daemon protocol
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The Line Printer Daemon protocol/Line Printer Remote protocol (or LPD, LPR) also known as the Berkeley printing system, is a set of programs that provide printer spooling and network print server functionality for Unix-like systems. The most common implementations of LPD are the official BSD UNIX operating system and the LPRng project. The Common Unix Printing System (or CUPS), which is more common on modern Linux distributions, borrows heavily from LPD. Commercial solutions are available that also leverage Berkeley printing protocol components, where more robust functionality and performance is necessary than is available from LPR/LPD (or CUPS) alone (such as might be required in large corporate environments).
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[edit] Commands
The official LPD protocol defines the following commands:
- lpr—Assign a job to a queue.
- lpq—Display the jobs assigned to a queue and their print status.
- lprm—Remove a job from a queue.
- lpc—Control a queue.
The lpd program provides the daemon and queues with which the aforementioned commands interface.
[edit] Usage
In order for a system to provide print functionality using LPD, the lpd program must be configured and started. Based upon its configuration, it will create the necessary queues and address the printers available to users of the system. Once started, it listens for local messages from the lpr, lpq, lprm, and lpc programs, as well as for network messages from remote clients who also implement the LPD protocol.
A printer that supports LPD/LPR is sometimes referred to as a "TCP/IP printer" (TCP/IP is used to establish connections between printers and workstations on a network), although that term seems equally applicable to a printer that supports CUPS.
[edit] References
[edit] See also
- Lp (Unix)
- LPRng
- Common Unix Printing System (CUPS)
- RLPR
- System V printing system
- print (command)
- Spooling
- Print server
- Application layer
- Foomatic
