A practical guide to Fedora and Red Hat Enterprise Linux, 7th Edition (2014)

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To define a class, first click the Administration tab at the top of the page and then click Add Class. At a minimum, you must enter a name for the class. You might also enter a description and location. The Members list displays the names of all CUPS printers and classes. Highlight the printers you want to be members of the class you are defining; hold SHIFT and click another printer to highlight more than one printer. To define a class that includes printers that are not adjacent in the list, define the class to have a single printer and then modify the class after you create it to add other printers. To modify existing classes, click Manage Classes in the Administration tab.

CUPS on the Command Line

In addition to using system-config-printer and the CUPS Web interface, you can control CUPS and manage print queues from the command line. This section describes the utilities that enable you to manage printers and print queues and establish printing quotas.

lpinfo: Displays Available Drivers

PPD files

The lpinfo utility provides information about the printer drivers and interfaces available to CUPS. The –m option displays the list of available PostScript Printer Definition (PPD) files/drivers.

$ lpinfo -m | head
foomatic:Alps-MD-1000-md2k.ppd Alps MD-1000 Foomatic/md2k
foomatic:Alps-MD-1000-ppmtomd.ppd Alps MD-1000 Foomatic/ppmtomd
foomatic:Alps-MD-1300-md1xMono.ppd Alps MD-1300 Foomatic/md1xMono
foomatic:Alps-MD-1300-md2k.ppd Alps MD-1300 Foomatic/md2k
foomatic:Alps-MD-1300-ppmtomd.ppd Alps MD-1300 Foomatic/ppmtomd
foomatic:Alps-MD-1500-md1xMono.ppd Alps MD-1500 Foomatic/md1xMono
foomatic:Alps-MD-1500-md2k.ppd Alps MD-1500 Foomatic/md2k
foomatic:Alps-MD-1500-ppmtomd.ppd Alps MD-1500 Foomatic/ppmtomd
foomatic:Alps-MD-2000-md2k.ppd Alps MD-2000 Foomatic/md2k
foomatic:Alps-MD-2000-ppmtomd.ppd Alps MD-2000 Foomatic/ppmtomd

URIs

CUPS uses URIs (page 561) to identify printer ports by type and location, just as a browser identifies documents by protocol and location. A parallel port has a URI with the format parallel:/dev/lp0; a remote LPD printer uses the format lpd://192.168.0.101, and a USB printer uses the format usb://Brother/HL-2140%20series. When run with root privileges, lpinfo with the –v option displays a list of available connections:

# lpinfo -v
network ipps
network ipp
network socket
network https
network http
network lpd
network beh
direct parallel:/dev/lp0
serial serial:/dev/ttyS0?baud=115200
serial serial:/dev/ttyS1?baud=115200
direct hp
network smb
direct hpfax
direct usb://Brother/HL-2140%20series?serial=L7J157453

The –v option to lpinfo does not display every possible network address for the socket, HTTP, IPP, LPD, and SMB protocols because there are more than 4 billion of these addresses in the IPv4 address space.

lpadmin: Configures Printers

You can use the lpadmin utility to add and remove printers from the system, modify printer configurations, and manage printer classes. This utility has three major options: –d (set the default printer), –x (remove a printer), and –p (add or modify a printer). The first two options are simple; examples follow the next subsection. Each of these three options takes the name of a printer as an argument. The name of the printer must start with a letter and cannot contain SPACEs.

Adding or Modifying a Printer

Add a printer or modify an existing printer by giving a command in the following format:

# lpadmin –p printer-name options

where printer-name is the name of the printer and options is a combination of options from the following list:

–c class

Adds the printer to the class class, creating the class if necessary.

–D info

The info is a string that describes the printer for the benefit of users; it has no meaning to the system. Enclose info within quotation marks if it contains SPACEs.

–E

Enables the printer, instructing CUPS to accept jobs into its print queue.

–L loc

The loc is a string that indicates the physical location of the printer (e.g., office, building, floor). It has no meaning to the system. Enclose loc within quotation marks if it contains SPACEs.

–m model

The model is the name of the PPD file (page 568) that describes the printer. Use lpinfo –m to display a list of installed PPD files. If you have a manufacturer-provided PPD file, copy it to /usr/share/cups/model. Use the –P option to specify the pathname of the file. Specifying –m postscript.ppd.gz, for example, is the same as specifying –P /usr/share/cups/model/postscript.ppd.gz.

–P file

The file is the absolute pathname of the PPD file (page 568) that describes the printer. Use lpinfo –m to display a list of installed PPD files. If you have a manufacturer-provided PPD file, copy it to /usr/share/cups/model. See –m for an alternate way to specify a PPD file.

–r class

Removes the printer from the class class. This option removes the class if, after removing the printer, the class would be empty.

–v URI

The URI is the device to which the printer is attached. Use lpinfo –v to list possible devices.

Example lpadmin Commands

At a minimum, you need to provide a device and a model when you add a printer to the system. The following command adds a Brother HL-2140 printer to the system and enables it for use. This printer is connected locally to a USB port and is named HL2140.

# lpadmin -p HL2140 -E -v usb://Brother/HL-2140%20series -m Brother-HL-2140-hpijs-pcl5e.ppd

The printer information generated by the preceding command is stored in the /etc/cups/printers.conf file:

# cat /etc/cups/printers.conf
# Printer configuration file for CUPS v1.6.3
# Written by cupsd on 2013-07-30 20:07
# DO NOT EDIT THIS FILE WHEN CUPSD IS RUNNING
<DefaultPrinter HL-2140-series>
Info Brother HL-2140 series
Location guava
MakeModel Brother HL-2140 Foomatic/hpijs-pcl5e (recommended)
DeviceURI usb://Brother/HL-2140%20series
State Idle
StateTime 1302648023
Type 8433684
Product (HL-2140 series)
Filter application/vnd.cups-raw 0 -
Filter application/vnd.cups-postscript 100 foomatic-rip
Filter application/vnd.cups-pdf 0 foomatic-rip
Filter application/vnd.cups-command 0 commandtops
Accepting Yes
Shared Yes
JobSheets none none
QuotaPeriod 0
PageLimit 0
KLimit 0
OpPolicy default
ErrorPolicy stop-printer
</Printer>

The lpadmin command decompresses and copies the printer driver information from the /usr/share/cups/model/stcolor.ppd.gz file to /etc/cups/ppd. The resulting file is given the printer’s name: /etc/cups/ppd/HL-2140-series.ppd.

You can modify a printer configuration with lpadmin using the same options that you used to add it. When you specify the name of an existing printer, lpadmin modifies the printer rather than creating a new one.

The next command configures an HP LaserJet–compatible printer with a JetDirect interface that is connected directly to the LAN at 192.168.1.103 and names this printer HPLJ. Specifying socket in the protocol part of the URI instructs CUPS to use the JetDirect protocol, a proprietary protocol developed by HP for printers connected directly to a network.

# lpadmin -p HPLJ -E -v socket://192.168.1.103 -m laserjet.ppd.gz

The lpstat utility with the –d option displays the name of the default printer:

# lpstat -d
system default destination: MainPrinter

CUPS automatically makes the first printer you define the default printer. The following command makes HPLJ the default printer:

#lpstat -d HPLJ

The following command removes the configuration for the HL2140 printer:

#lpstat -x HL2140

Printing Quotas

CUPS provides rudimentary printing quotas. You can define two forms of quotas: page count and file size. File size quotas are almost meaningless because a small PostScript file can take a long time to interpret and can require a lot more ink to print than a large one. Page quotas are more useful, although their implementation is flawed. To determine the number of pages in a document, CUPS examines the PostScript input. If a job is submitted in the printer’s native language, such as PCL, CUPS bypasses this accounting mechanism. Also, if mpage is used to create a PostScript file with multiple pages printed on each sheet, CUPS counts each page in the original document, rather than each sheet of paper it prints on.

Use job-quota-period and either job-page-limit or job-k-limit to establish a quota for each user on a given printer. The job-quota-period option specifies the number of seconds that the quota remains valid. The following command establishes a quota of 20 pages per day per user for the printer named HPLJ:

#lpadmin -p HPLJ -o job-quota-period=86400 -o job-page-limit=20

The job-k-limit option works similarly but defines a file size limit in kilobytes. The limit is the total number of kilobytes that each user can print during the quota period. After a user has exceeded her quota, she will not be allowed to print until the next quota period.

Managing Print Queues

When a printer is operating normally, it accepts jobs into its print queue and prints those jobs in the order in which they are received. You can give the command cupsreject followed by the name of a printer to cause a printer to not accept jobs into its print queue; enter the commandcupsaccept to re-enable it. You can also use system-config-printer to control the print queue; refer to “Settings” on page 559. Two factors determine how a printer handles a job: if the printer is accepting jobs and if it is enabled. Table 13-1 on page 560 describes what happens with the various combinations of the two factors.

The utilities that change these factors are cupsdisable, cupsenable, cupsreject, and cupsaccept. Each utility takes the name of a printer as an argument. The following commands first disable and then enable the printer named HPLJ:

# cupsdisable HPLJ
# cupsenable HPLJ

The next commands cause HPLJ to reject and then accept jobs:

# cupsreject HPLJ
# cupsaccept HPLJ

Sharing CUPS Printers

This section describes how to use textual tools to share local printers. Alternately, you can use system-config-printer (page 558) to share printers: Display the Server Settings window by selecting menubar: ServerSettings and put a tick in the check box labeled Publish shared printers connected to this system. Using this technique allows you to choose whether to share each printer.

IPP facilitates remote printing. The Listen directive in the CUPS configuration file, /etc/cups/cupsd.conf, specifies which IP address and port or which domain socket path CUPS binds to and accepts requests on. The Listen directive has the following format:

Listen IP:port | path

where IP is the IP address that CUPS accepts connections on, port is the port number that CUPS listens on for connections on IP, and path is the pathname of the domain socket CUPS uses to communicate with printers. CUPS typically uses port 631 and by default binds to localhost. Thus it accepts connections from the loopback service of the local system only. CUPS uses /var/run/cups/cups.sock, a local domain socket, to communicate with local printers. It can also use a Port directive to specify the port number it listens to for HTTP requests.

$ grep -i listen /etc/cups/cupsd.conf
# Only listen for connections from the local machine.
Listen localhost:631
Listen /var/run/cups/cups.sock

To allow other systems to connect to the CUPS server on the local system, you must instruct CUPS to bind to an IP address that the other systems can reach. First remove or comment out the Listen localhost:631 directive; leave the other Listen directive in place:

# Listen localhost:631
Listen /var/run/cups/cups.sock

In place of the commented-out Listen directive, use an access control list to permit only selected machines to connect to local printers. An access control list is defined inside a <Location> container (see page 948 for the Apache equivalent). The following example allows only the system at IP address 192.168.1.101 and the local system to print to the specified printer.

<Location />
Order Allow,Deny
# Allow access from the local system and 192.168.1.101
Allow from localhost
Allow from 192.168.1.101
# Uncomment the following to permit access from all local interfaces
# Allow @LOCAL
</Location>

The @LOCAL macro is internal to CUPS and specifies the local system. This macro accepts communication from any address that resolves to the local system. Specify Allow @LOCAL to share the printer with all local interfaces.

When you change cupsd.conf, you must restart the cupsd daemon (page 557).

The Order Allow,Deny directive denies print requests by default and allows requests from specified addresses. An Order Deny,Allow directive would allow access by default and denies access only to clients specified in Deny from directives. You can use domain names, including wildcards, and IP ranges with either wildcards or net-masks in Allow from and Deny from directives. These directives work the same way they do in Apache. For more information refer to “Order” on page 961.

With the Order Deny,Allow directive, Deny from specifies the only IP addresses CUPS does not accept connections from. When you use the Order Allow,Deny directive, Allow from specifies the only IP addresses CUPS accepts connections from.

After you restart cupsd, remote systems can print on the local system’s printers using the IP address and port number specified by the Listen directive. If the server is running a firewall, you need to allow remote systems to connect through it on port 631; see page 557. You might also need to modify the SELinux policy (page 475) depending on the system setup.

Traditional UNIX Printing

Before the advent of GUIs and WYSIWYG (page 1281) word processors, UNIX users would create documents using an editor such as vi and a typesetting markup language such as TeX or nroff/troff, convert the resulting files to PostScript using an interpreter, and send the PostScript files to the printer using lpr (BSD) or lp (System V). Linux implements both BSD and System V command-line printing utilities for compatibility. However, these utilities are now wrappers around the equivalent functionality in CUPS rather than core components of the printing system. The corresponding utilities are functionally equivalent; use whichever you prefer (Table 13-2).

Table 13-2 BSD and System V command-line print utilities

From the command line, you can print a text, PostScript, or PDF file using lp:

$ lp memo.txt
request id is MainPrinter-25 (1 file(s))

The preceding command adds memo.txt to the print queue of the default printer and assigns it job number 25. When this printer is available, it prints the file. You can specify a printer using the –d option:

$ lp -d HL2140 graph.ps
request id is HL2140-26 (1 file(s))

The lpr –P option is equivalent to the lp –d option.

Without arguments, lp and lpr send their standard input to the printer:

$ cat memo2.txt | lp
request id is MainPrinter-27 (1 file(s))

The lpq and lpstat commands display information about the print queue:

$ lpstat
MainPrinter-25 zach 13312 Sun Feb 23 18:28:38 2014
HL2140-26 zach 75776 Sun Feb 23 18:28:48 2014
MainPrinter-27 zach 8192 Sun Feb 23 18:28:57 2014

Use cancel or lprm to remove jobs from the print queue. By default, only the owner of a print job or a user working with root privileges can remove a job.

$ cancel 27
$ lpstat
MainPrinter-25 zach 13312 Sun Feb 23 18:28:38 2014
HL2140-26 zach 75776 Sun Feb 23 18:28:48 2014

While working with root privileges, give the command cancel –a or lprm – to remove all jobs from the print queues.

Printing from Windows

This section explains how to use printers on Linux CUPS servers from Windows machines. CUPS is easier to manage and can be made more secure than using Samba to print from Windows.

Printing Using CUPS

Modern versions of Windows (2000 and later) support IPP and as a result can communicate directly with CUPS. To use this feature, you must have CUPS configured on the Linux print server to allow remote IPP printing; you also need to create a new printer on the Windows system that points to the IP address of the Linux print server.

First set up the /etc/cups/cupsd.conf file to allow network printing from a client, as explained in “Sharing CUPS Printers” on page 572. Setting up CUPS to allow printing from a Windows machine is exactly the same as setting it up to allow printing from a Linux client system. If necessary, open the firewall as explained on page 557.

Windows XP

From Windows XP, go to Control PanelPrinters and Faxes and click Add Printer. Click Next in the introductory window and select A network printer or a printer attached to another computer. Click Next. Select Connect to a printer on the Internet or on a home or office network. Continue following the next paragraph at “Enter URL.”

Windows 7

From Windows 7, go to Control PanelDevices and Printers and click Add a printer. Click Add a network, wireless, or Bluetooth printer. Assuming Windows does not find the printer, click The printer that I want isn’t listed. Click the radio button labeled Select a shared printer by name.

Enter URL

Enter the following information in the text box (under Windows XP it is labeled URL):

http://hostname:631/printers/printer-name

where hostname is the name or IP address of the Linux CUPS server system and printer-name is the name of the printer on that system. For example, for the printer named dog88 on the system named dog at IP address 192.168.0.12, you could enter http://dog:631/printers/dog88 orhttp://192.168.0.12:631/printers/dog88. If you use a hostname, it must be defined in the hosts file on the Windows machine. Click Next. Windows requests that you specify the manufacturer and model of the printer or provide a driver for the printer. If you supply a printer driver, use the Windows version of the driver.

After Windows copies some files, the printer appears in the Printers and Faxes/Devices and Printers window. Under Windows 7 you need to click through two more screens. Right-click the printer and select Set as Default Printer to make it the default printer. You can specify comments, a location, and other attributes of the printer by right-clicking the printer and selecting Properties or Printer Properties.

Printing Using Samba

This section assumes that Samba (page 827) is installed and working on the Linux system that controls the printer you want to use from Windows. Samba must be set up so that the Windows user who will be printing is mapped to a Linux user (including mapping the Windows guest user to the Linux user nobody). Make sure these users have Samba passwords. Refer to “Samba Users, User Maps, and Passwords” on page 829.

Windows supports printer sharing via SMB, which allows a printer to be shared transparently between Windows systems using the same mechanism as file sharing.

Samba allows Windows users to use printers connected to Linux systems just as they would use any other shared printers. Because all Linux printers traditionally appear to be PostScript printers, the Linux print server appears to share a PostScript printer. Windows does not include a generic PostScript printer driver. Instead, Windows users must select a printer driver for a PostScript printer. The Apple LaserWriter 12/640ps driver is a good choice.

When you use rpm to install Samba, it creates a directory named /var/spool/samba that is owned by the root account and that anyone can read from and write to. The sticky bit (page 1275) is set for this directory, allowing a Windows user who starts a print job as a Linux user to be able to delete that job, but denying users the ability to delete the print jobs of other users. Make sure this directory is in place and has the proper ownership and permissions:

$ ls -ld /var/spool/samba
drwxrwxrwt. 2 root root 4096 02-03 15:23 /var/spool/samba

Uncomment following two lines in the [global] section of the /etc/samba/smb.conf file.

[global]
...
printing = cups
printcap name = cups

The printer’s share is listed in the [printers] section in smb.conf. In the following example, the path is the path Samba uses as a spool directory and is not a normal share path. The settings allow anyone, including guest, to use the printer. The [printers] section in the default smb.conf file has the following entries, which are appropriate for most setups:

[printers]
comment = All Printers
path = /var/spool/samba
browseable = no
guest ok = no
writable = no
printable = yes

Ideally each user who plans to print should have an account. Otherwise, when multiple users share the same account (e.g., the nobody account), they can delete one another’s print jobs.

Printing to Windows

CUPS views a printer on a Windows machine exactly the same way it views any other printer. The only difference is the URI you need to specify when connecting it. To configure a printer connected to a Windows machine, click the Administration tab in the CUPS Web interface and selectAdd Printer, just as you would for a local printer.

When you are asked to select the device, choose Windows Printer via SAMBA. Enter the URI of the printer in the following format:

smb://windows_system/printer_name

where windows_system can be an IP address or a hostname. After you have added the printer, you can use it as you would any other printer.

Alternately, you can use system-config-printer (page 558) to set up a Windows printer. When you choose to install a Windows printer, you can specify a URL as described previously, or you can click Browse. By default, this setup prompts the user if authentication is required; you can choose Set authentication details now if you prefer.

Chapter Summary

A printing system such as CUPS sets up printers. It also moves print jobs from an application or the command line through the appropriate filters and into a queue for a suitable printer and then prints those jobs.

CUPS is a cross-platform print server built around IPP (Internet Printing Protocol). It handles setting up and sending jobs through print queues. The easiest way to configure printers is using Printers from the Settings window or the Print Settings window (system-config-printer). You can also configure CUPS using the Web interface, which you can access by pointing a Web browser at localhost:631 on the system the printer is connected to. From the Web interface, you can configure print queues and modify print jobs in the queues.

You can use the traditional UNIX commands from a command line to send jobs to a printer (lpr/lp), display a print queue (lpq/lpstat), and remove jobs from a print queue (lprm/cancel). In addition, CUPS provides the lpinfo and lpadmin utilities, which allow you to configure printers from the command line.

CUPS and Samba enable you to print on a Linux printer from a Windows machine and vice versa.

Exercises

1. Which commands can you use from the command line to send a file to the default printer?

2. Which command would you give to cancel all print jobs on the system?

3. Which commands list your outstanding print jobs?

4. What is the purpose of sharing a Linux printer using Samba?

5. Name three printing protocols that CUPS supports. Which is the CUPS native protocol?

Advanced Exercises

6. Which command lists the installed printer drivers available to CUPS?

7. How would you send a text file to a printer connected to the first parallel port without using a print queue? Why is doing so a bad idea?

8. Assume you have a USB printer with a manufacturer-supplied PostScript printer definition file named newprinter.ppd. Which command would you use to add this printer to the system on the first USB port with the name USBPrinter?

9. How would you define a quota that allows each user to print up to 50 pages per week to the printer named LaserJet?

10. Define a set of access control rules for a <Location> container inside /etc/cups/cupsd.conf that would allow anyone to print to all printers as long as they were either on the local system or in the mydomain.com domain.