See this page as a slide show

Chapter 26: Printing

Colorado State University

Computer Science Department

Original slides from Dr. James Walden at Northern Kentucky University.

Printing

1. Printer Languages
2. Printing Systems
3. CUPS Printing
4. Troubleshooting
5. System V Printing
6. BSD Printing
7. Printer Practicalities

Printer Languages

• PostScript (.ps): Most common page description language on Unix and Linux systems, from Adobe.
• PDF (.pdf): Portable document format from Adobe, not a page description language, usually translated.
• PCL (.pcl): Printer control language from Hewlett-Packard, binary format for laser and inkjet printers.
• XHTML (.xhtml): Markup language for printing based on XML specification.
• XPS (.xps): XML Paper Specification from Microsoft, not currently very widely used.
• PJL (.pjl): Printer Job Language from HP uses metalanguage to describe printer jobs.

PostScript

PostScript is a Page Description Language (PDL) that was invented around the same time as the laser printer.

• Now is the most common PDL on Unix and Linux systems, and many printers can directly interpret.
• Developed by Adobe Systems, but evolved from InterPress, a Xerox proprietary language.
• You can read most PostScript programs with a text editor, not a binary format.
• Interpreted by a PostScript-specificRaster Image Processor (RIP) that produces a bitmap.

PDF

Portable Document Format (PDF) from Adobe systems was designed for the interchange of documents.

• Currently dominates this market, almost every other tool export to PDF (Microsoft Word, PowerPoint, etc.)
• Not a page description language, but many convertors exist between PDF and PS or PCL.
• Adobe Acrobat provides a downloadable reader and proprietary tools for generating PDF content:
  • Adobe Reader 9 (2010), Adobe Reader X (2012)
  • PDF 1.7 (2008), PDF 2.0 (2011)

PCL

Printer Command Language (PCL) was invented by Hewlett-Packard for its laser and inkjet printers.

• PCL is a page description language that tells printers how to print pages.
• PCL jobs are binary, not human readable, so must be manipulated by tools.
• HP has a PCL dialect with custom commands that take advantage of specific printer features:
  • PCL6: Drawing tools, color handling, paper handling, font loading, compresion etc.

XHTML

Extensible HyperText Markup Language (XHTML) is recommended by the World Wide Web consortium.

• Cleaner version of HTML, based on well-formed XML specification that can be parsed in a standard fashion.
• XHTML-Print provides a data stream, e.g., from a Web page to be rendered on low end printers.
  • Example: you can browse the web and print a web page from a Bluetooth printer
  • Mostly used by content management systems based on web pages.

Printing Systems

• Major printing systems: CUPS, BSD, System V are the historical systems used on Unix and Linux.
• Based on a print spooler or queuing system for scheduling print jobs.
• Requires user-level utilities based on CLI or GUI that allows the user to queue, cancel, or query jobs.
• Back end drivers and software to communicate with the actual printing devices (local or network).
• Network protocols that allow print spoolers to communicate and transfer jobs.

CUPS Overview

• Common Unix Printing System (CUPS) is a standards-based open source printing system.
• Original developed by Apple for OS X and other Unix environments.
• A CUPS server is a spooler that maintains print queues for clients, with a client-server architecture.
• The client can use either command line interfaces (lpr, lpq) or a graphical interface (kprinter).
• Also supports a web interface to configure and administer printer jobs.

CUPS Printing

• Client transmits copies of the files to the CUPS server, which reads them and stores them in a queue.
• The CUPS server then will process each file as the printer becomes available.
• The CUPS server examines both the printer’s postscript capabilities and the document to make sure it prints properly on the device.

CUPS Printing

• Preparation for a job requires the CUPS to pass it through a pipeline of filters which perform a variety of functions.
  • Reformat if necessary
  • Transfer a job from one PDL to another
  • Printer initialization
• Then the document finally gets passed to the last stage which is the pipeline that sends the job from the host via the appropriate protocol, e.g. USB port.

CUPS Commands

• Commands allow the user to queue, suspend, cancel, or send jobs from one queue to another.
• lpr: asks the CUPS server to queue a print job

    lpr -P laser01 myfile.ps

• lpq: requests job status from the CUPS server

    lpq -P laser01

• lpstat: summary of CUPS server

    lpstat -t

• lprm: remove a print job from the CUPS server

    lprm <id>

CUPS Web Interface

Multiple Printers

• CUPS will manage multiple queues for multiple printers.
• A simple -p option will specify which printer queue to use.
• You may also set a default printer in two different ways:
  • PRINTER environment variable

    export PRINTER=printer_name

• Telling CUPS via a command

    lpotions -dprinter_name

Printer Instances

• These allow you to set several instances for different printing types, like a draft print, or a normal print.

    lpoptions -p laser02/2up -o number-up=2

• Creates instance laser02 that performs 2-up printing

Network Printing

• All CUPS daemons communicate with each other, which makes it easy with multiple computers.
• To configure CUPS daemon to accept print jobs edit the file /etc/cups/cupsd.conf.
• To allow two printers on two different subnets to communicate, edit the file to set up a slave server.
• The configuration file will also allow you to set up multiple queues for one printer.

CUPS Protocol

• The underlying protocol for CUPS is HTTP that uses port 631
• CUPS servers are web servers, clients can be GUI or CLI or a web interface
• Uses Internet Printing Protocol (IPP) based on simple GET and POST commands.

CUPS Administration

• Responsibilities of a CUPS server administrator:
  • Install printers
  • Route network Printers
  • Setup authorization
  • Editing configuration files
  • Specifying paper size
  • Printer maintenance!
• Linux system components of a CUPS server
  • cupsd — daemon process that manage print jobs
  • /etc/cups/cupsd.conf — configuration file

CUPS Administration

• Used on Unix, Linux, and Mac operating systems
• Any printer that can be networked
• Any server that can act as a CUPS server
• Handy browser interface for easy maintenance
• Centralized system for printing and management
  • Standardized
  • Efficient for large printers
  • Printer-specific Information
• Can print multiple printer file formats
  • pdf, dvi, gif, jpeg, tiff, and more

CUPS Implementation

• What you need: Printer, Server, Client
• Connect server to network via config files
• Use the web interface to configure the rest
• It’s in a package:

    # apt-get install cups

Remote CUPSing

• You’d be crazy to configure CUPS on every computer at your site.
• Instead, have one central print server, that is running cupsd.
• On all other machines, just configure /etc/cups/client.conf:

$ cat /etc/cups/client.conf
servername parsons.cs.colostate.edu

CUPS Documentation

• Nemeth, E, Snyder, G, & Hein, T (2011) Unix and Linux Administration Handbook Fourth Edition, Prentice Hall
• Wikipedia: CUPS Common Unix Printing System retrieved Sep. 2012 from https://en.wikipedia.org/wiki/CUPS
• Common UNIX Printing System. Open source project page retrieved on Sep. 2012 from http://www.cups.org/

Troubleshooting

• If you change the cupsd.conf file, be sure to restart the daemon
• Logging
  • Page log: list of pages printed
  • Access log: requests processed by server
  • Error log: printer or server errors
  • All typically kept under /var/log

Troubleshooting

Problem	Where to look
Name resolution, permissions	System log files on sending machine
Permissions	System log files on print server
Missing filters, unknown printers, missing dirs, etc.	CUPS log files on sending machine
Messages about bad device names, bad formats, etc.	CUPS log files on print server

System V Printing

Command	Location	Function
accept	/usr/sbin	make queue accept printing jobs
cancel	/bin	remove print job from queue
disable	/bin	disable printing jobs from a queue
enable	/bin	enable printing jobs from a queue
lp	/bin	queues jobs for printing
lpadmin	/usr/sbin	configure the printing system
lpmove	/usr/sbin	move printing jobs between queues
lpsched	/usr/lib	schedules and prints jobs
lpshut	/usr/sbin	stops printing services
lpstat	/bin	reports status of printing services
reject	/usr/sbin	make queue reject printing jobs

BSD Printing

Command	Location	Function
lpc	/usr/sbin	controls a printer or queue
lpd	/usr/sbin	schedules and prints jobs
lpq	/usr/bin	show print queue and status
lpr	/usr/bin	queues jobs for printing
lprm	/usr/bin	cancels a queued print job
lptest	/usr/bin	prints a test page

Printer Practicalities

• Printer selection
  • Supported well by Linux?
    • https://wiki.linuxfoundation.org/openprinting/start
  • PS, non-PS?
• GDI (Graphics Device Interface) printers
  • WinPrinters
  • Supported better by Windows

Printer Practicalities (cont.)

• Duplexing
  • Do you really need it?
• Accessories
  • Memory
    • Large documents
  • Trays
• Serial or parallel?
• Network printers
  • Network interfaces
    • Faster
    • Better for large networks

Printer Practicalities (cont.)

• Turn off banner pages
  • Waste of toner/paper
• Recycle!
• User print previewers
• Printers are cheap, ink/toner are not
  • Monitor cost/page
  • PaperCut

Printer Practicalities (cont.)

• What’s it going to cost me?
• Depends on the size of the printer
  • Larger, more efficient
  • Smaller, more costly
  • Printers cost $200–$10000
• Total cost of ownership greatly exceeds the original purchase price
• Maintenance costs are high if you have to call a service technician
• Laser printers are generally more cost effective per page of printing