What is cups in linux

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CUPS is the standards-based, open source printing system currently developed by Apple Inc. for macOS® and other UNIX®-like operating systems.

Installation

Optionally, install the cups-pdf package if you intend to «print» into a PDF document. By default, PDF files are stored in /var/spool/cups-pdf/username/ . The location can be changed in /etc/cups/cups-pdf.conf .

Then enable and start cups.service or alternatively use socket activation to only start CUPS when a program wants to use the service.

Socket activation

cups provides a cups.socket unit. If cups.socket is enabled (and cups.service is disabled), systemd will not start CUPS immediately; it will just listen to the appropriate sockets. Then, whenever a program attempts to connect to one of these CUPS sockets, systemd will start cups.service and transparently hand over control of these ports to the CUPS process.

Print steps

It is important to know how CUPS works if wanting to solve related issues:

An application sends a PDF file to CUPS when ‘print’ has been selected (in case the application sends another format, it is converted to PDF first).
CUPS then looks at the printer’s PPD file (printer description file) and figures out what filters it needs to use to convert the PDF file to a language that the printer understands (like PJL, PCL, bitmap or native PDF).
The filter converts the PDF file to a format understood by the printer.
Then it is sent to the back-end. For example, if the printer is connected to a USB port, it uses the USB back-end.

Connection interfaces

Additional steps for printer detection are listed below for various connection interfaces.

To see if your USB printer is detected, make sure you have the usbutils package installed, then:

Parallel port

To use a parallel port printer, the lp , parport and parport_pc kernel modules are required.

Network

To discover, make use of discovered or share printers using DNS-SD/mDNS, setup .local hostname resolution with Avahi and restart cups.service .

To share printers with Samba, e.g. if the system is to be a print server for Windows clients, the samba package will be required.

Printer drivers

This article or section needs expansion.

The drivers for a printer may come from any of the sources shown below. See CUPS/Printer-specific problems for an incomplete list of drivers that others have managed to get working.

To drive a printer, CUPS needs a PPD file and, for most printers, some filters. For details on how CUPS uses PPDs and filters, see [1].

The OpenPrinting Printer List provides driver recommendations for many printers. It also supplies PPD files for each printer, but most are available through foomatic or the recommended driver package.

When a PPD file is provided to CUPS, the CUPS server will regenerate the PPD files and save them in /etc/cups/ppd/ .

CUPS includes support for AirPrint and IPP Everywhere printers.

OpenPrinting CUPS filters

The Linux Foundation’s OpenPrinting workgroup provides cups-filters. Those are backends, filters, and other binaries that were once part of CUPS but are no longer maintained by Apple. They are available in the cups-filters package that is a dependency of cups .

Non-PDF printers require ghostscript to be installed. For PostScript printers, gsfonts may also be required.

Foomatic

The Linux Foundation’s OpenPrinting workgroup’s foomatic provides PPDs for many printer drivers, both free and non-free. For more information about what foomatic does, see Foomatic from the Developer’s View.

To use foomatic, install foomatic-db-engine and at least one of:

foomatic-db — a collection of XML files used by foomatic-db-engine to generate PPD files.
foomatic-db-ppds — prebuilt PPD files.
foomatic-db-nonfree — a collection of XML files from printer manufacturers under non-free licenses used by foomatic-db-engine to generate PPD files.
foomatic-db-nonfree-ppds — prebuilt PPD files under non-free licenses.

The foomatic PPDs may require additional filters, such as min12xxw AUR .

Gutenprint

The Gutenprint project provides drivers for Canon, Epson, Lexmark, Sony, Olympus, and PCL printers for use with CUPS and GIMP.

Manufacturer-specific drivers

Many printer manufacturers supply their own Linux drivers. These are often available in the official Arch repositories or in the AUR.

Some of those drivers are described in more detail in CUPS/Printer-specific problems.

Printer URI

Listed below are additional steps to manually generate the URI if required. Some printers or drivers may need a special URI as described in CUPS/Printer-specific problems.

CUPS should be able to automatically generate a URI for USB printers, for example usb://HP/DESKJET%20940C?serial=CN16E6C364BH .

If it does not, see CUPS/Troubleshooting#USB printers for troubleshooting steps.

Parallel port

The URI should be of the form parallel:device . For instance, if the printer is connected on /dev/lp0 , use parallel:/dev/lp0 . If you are using a USB to parallel port adapter, use parallel:/dev/usb/lp0 as the printer URI.

Network

If you have set up Avahi as in #Network, CUPS should detect the printer URI. You can also use avahi-discover to find the name of your printer and its address (for instance, BRN30055C6B4C7A.local/10.10.0.155:631 ).

The URI can also be generated manually, without using Avahi. A list of the available URI schemes for networked printers is available in the CUPS documentation. As exact details of the URIs differ between printers, check either the manual of the printer or CUPS/Printer-specific problems.

The URI for printers on SMB shares is described in the smbspool(8) man page.

For example, smb://BEN-DESKTOP/HP Color LaserJet CP1510 series PCL6 becomes smb://BEN-DESKTOP/HP%20Color%20LaserJet%20CP1510%20series%20PCL6 .

This result string can be obtained by running the following command:

Remote CUPS print servers can be accessed through a URI of the form ipp://hostname:631/printers/queue_name . See CUPS/Printer sharing#Printer sharing for details on setting up the remote print server.

See CUPS/Troubleshooting#Networking issues for additional issues and solutions.

Usage

CUPS can be fully controlled using the lp* and cups* CLI tools. Alternatively, the #Web interface or one of several #GUI applications can be used.

The queue name is a short but descriptive name used on the system to identify the queue. This name should not contain spaces or any special characters. For instance, a print queue corresponding to a HP LaserJet 5P could be named «hpljet5p». More than one queue can be associated with each physical printer.
The location is a description of the printer’s physical location (for instance «bedroom», or «kitchen»). This is to aid in maintaining several printers.
The description is a full description of the print queue. A common use is a full printer name (like «HP LaserJet 5P»).

CLI tools

See CUPS local documentation for more tips on the command-line tools.

This article or section needs language, wiki syntax or style improvements. See Help:Style for reference.

The queue_name is up to you. Examples:

Check the status Deactivate a printer Activate a printer Set the printer to accept jobs Remove a printer.

First set it to reject all incoming entries:

Then disable it:

Finally remove it:

Print a test page Print a file Check the queue Clear the queue View ink levels

Add your user to the lp user group:

Log out and log in again.

For usage information, use:

Web interface

The CUPS server can be fully administered through the web interface, available on http://localhost:631/.

To perform administrative tasks from the web interface, authentication is required; see #Permissions.

Go to the Administration page.

Modify existing queues

Go to the Printers page, and select a queue to modify.

Go to the Printers page, and select a queue.

GUI applications

If your user does not have sufficient privileges to administer CUPS, the applications will request the root password when they start. To give users administrative privileges without needing root access, see #Configuration.

Configuration

The CUPS server configuration is located in /etc/cups/cupsd.conf and /etc/cups/cups-files.conf (see cupsd.conf(5) and cups-files.conf(5) ). After editing either file, restart cups.service to apply any changes. The default configuration is sufficient for most users.

Permissions

User groups with printer administration privileges are defined in SystemGroup in the /etc/cups/cups-files.conf . The sys and root and wheel groups are used by default.

CUPS helper programs are run as the cups user and group. This allows the helper programs to access printer devices and read configuration files in /etc/cups/ , which are owned by the cups group.

Default paper size

cups is built with libpaper support and libpaper defaults to the Letter paper size (called PageSize in lpoptions ). To avoid having to change the paper size for each print queue you add, edit /etc/papersize and set your system default paper size. See papersize(5) .

Log files

By default, all logs are sent to files in /var/log/cups/ . By changing the values of the AccessLog , ErrorLog , and PageLog directives in /etc/cups/cups-files.conf to syslog , CUPS can be made to log to the systemd journal instead. See Fedora:Changes/CupsJournalLogging for information on the original proposed change.

cups-browsed

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CUPS can use Avahi browsing to discover unknown shared printers in your network. This can be useful in large setups where the server is unknown. To use this feature, set up .local hostname resolution, and start both avahi-daemon.service and cups-browsed.service . Jobs are sent directly to the printer without any processing so the created queues may not work, however driverless printers such as those supporting IPP Everywhere or AirPrint should work out of the box.

Print servers and remote administration

Allowing admin authentication through PolicyKit

PolicyKit can be configured to allow users to configure printers using a GUI without the admin password.

Here is an example that allows members of the wheel user group to administer printers without a password:

Without a local CUPS server

CUPS can be configured to directly connect to remote printer servers instead of running a local print server. This requires installation of the libcups package. Some applications will still require the cups package for printing.

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Сервер печати CUPS

Содержание

Сервер печати CUPS

Первичный (основной) механизм для печати и сервисов печати в Ubuntu — это Общая система печати UNIX (Common UNIX Printing System — CUPS). Данная система печати — это свободный, доступный и переносимый слой, который стал новым стандартом печати для большинства дистрибутивов Linux.

CUPS управляет заданиями печати и обеспечивает сетевую печать с использованием стандарта IPP (интернет протокол печати), поддерживая огромный список принтеров от матричных до лазерных и любых других. CUPS также поддерживает PostScript описание принтеров (PPD) и автоопределение сетевых принтеров, а также простую настройку и администрирование через web интерфейс.

Установка

Для установки CUPS на ваш Ubuntu компьютер просто используйте sudo для выполнения команды apt-get, передав ей названия пакетов в качестве параметра. Полная установка CUPS содержит много зависимостей, но они все могут быть определены в одной команде. Введите следующее в терминале для установки CUPS:

После аутентификации вас по паролю, пакеты должны загрузиться и установиться без ошибок. В заключении установки сервер CUPS будет запущен автоматически.

При необходимости решения проблем, вы можете получить доступ к ошибкам сервера CUPS через файл журнала /var/log/cups/error_log. Если журнал ошибок не дает достаточно информации для решения какой-либо проблемы, уровень журналирования CUPS можно повысить изменением директивы LogLevel в файле настроек (описывается ниже) до debug или даже debug2 со стандартного info, что будет сохранять в журнал абсолютно все. Если вы проведете такое изменение, не забудьте вернуть все обратно после решения проблемы, чтобы избежать излишнего разрастания файла журнала.

Настройка

Прежде чем редактировать файл настроек, вам стоит сделать копию оригинального файла и защитить ее от записи, чтобы у вас были оригинальные настройки в качестве руководства, которые можно восстановить при необходимости.

Скопируйте и защитите от записи файл /etc/cups/cupsd.conf.original с помощью следующих команд в терминале:

1. ServerAdmin: Для настройки email адреса назначенного администратора CUPS сервера, просто откройте на редактирование файл /etc/cups/cupsd.conf с помощью своего любимого текстового редактора, и добавьте или измените строку ServerAdmin соответствующим образом. Например, если вы администратор CUPS сервера и ваш email адрес ‘bjoy@somebigco.com’, вам следует изменить строку ServerAdmin следующим образом:

2. Listen: В Ubuntu по умолчанию установленный CUPS сервер слушает только интерфейс обратной петли по адресу 127.0.0.1. Чтобы заставить CUPS сервер прослушивать актуальный IP адрес сетевого адаптера, вы должны указать сетевое имя или пару IP адрес/порт добавочной директивой Listen. Например, если ваш сервер находится в локальной сети с IP адресом 192.168.10.250 и вы хотите сделать его доступным для других систем в этой подсети, отредактируйте /etc/cups/cupsd.conf, добавив директиву Listen, как показано ниже:

В приведенном примере вы можете закомментировать или удалить ссылки на адрес обратной петли (127.0.0.1), если вы не хотите, чтобы cupsd прослушивал этот интерфейс, а только Ethernet интерфейсы локальной сети. Чтобы разрешить прослушивать все сетевые интерфейсы, назначенные определенному сетевому имении, включая обратную петлю, вы можете создать такую запись Listen для имени (например) socrates:

или опустить директиву Listen и использовать вместо нее Port:

Для дополнительных примеров по директивам в файле настройки CUPS, смотрите ассоциированную страницу системного руководства, введя в терминале следующую команду:

Web интерфейс

Чтобы выполнить административную задачу через web интерфейс, вы должны либо разрешить учетную запись root на своем сервере, либо авторизоваться как пользователь из группы lpadmin. По соображениям безопасности CUPS не авторизует пользователей с пустыми паролями.

Чтобы добавить пользователя в группу lpadmin, выполните в терминале следующую команду:

Дальнейшая документация доступна через закладку Documentation/Help web интерфейса.

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What is cups in linux