Developer(s) | The Debian Project |
---|---|
Initial release | 31 March 1998 [1] |
Stable release | |
Repository | |
Written in | C++, [3] shell script, [3] Extensible Markup Language, [3] CMake, [3] C, [3] Perl [3] |
Operating system | Unix-like |
Type | Package manager |
License | GPLv2+ |
Website | wiki |
Advanced package tool, or APT, is a free-software user interface that works with core libraries to handle the installation and removal of software on Debian and Debian-based Linux distributions. [4] APT simplifies the process of managing software on Unix-like computer systems by automating the retrieval, configuration and installation of software packages, either from precompiled files or by compiling source code. [4]
APT is a collection of tools distributed in a package named apt. A significant part of APT is defined in a C++ library of functions; APT also includes command-line programs for dealing with packages, which use the library. Three such programs are apt
, apt-get
and apt-cache
. They are commonly used in examples because they are simple and ubiquitous. The apt package is of "important" priority in all current Debian releases, and is therefore included in a default Debian installation. APT can be considered a front end to dpkg
, friendlier than the older dselect
front end. While dpkg
performs actions on individual packages, APT manages relations (especially dependencies) between them, as well as sourcing and management of higher-level versioning decisions (release tracking and version pinning).
APT is often hailed as one of Debian's best features, [5] [6] [7] [8] which Debian developers attribute to the strict quality controls in Debian's policy. [9] [10]
A major feature of APT is the way it calls dpkg
— it does topological sorting of the list of packages to be installed or removed and calls dpkg
in the best possible sequence. In some cases, it utilizes the --force
options of dpkg
. However, it only does this when it is unable to calculate how to avoid the reason dpkg
requires the action to be forced.
The user indicates one or more packages to be installed. Each package name is phrased as just the name portion of the package, not a fully qualified filename (for instance, in a Debian system, libc6
would be the argument provided, not libc6_1.9.6-2.deb
). Notably, APT automatically gets and installs packages upon which the indicated package depends (if necessary). This was an original distinguishing characteristic of APT-based package management systems, as it avoided installation failure due to missing dependencies, a type of dependency hell.
Another distinction is the retrieval of packages from remote repositories. APT uses a location configuration file (/etc/apt/sources.list
) to locate the desired packages, which might be available on the network or a removable storage medium, for example, and retrieve them, and also obtain information about available (but not installed) packages.
APT provides other command options to override decisions made by apt-get's conflict resolution system. One option is to force a particular version of a package. This can downgrade a package and render dependent software inoperable, so the user must be careful.
Finally, the apt_preferences
mechanism allows the user to create an alternative installation policy for individual packages.
The user can specify packages using a POSIX regular expression.
APT searches its cached list of packages and lists the dependencies that must be installed or updated.
APT retrieves, configures and installs the dependencies automatically.
Triggers are the treatment of deferred actions.
Usage modes of apt
and apt-get
that facilitate updating installed packages include:
update
is used to resynchronize the package index files from their sources. The lists of available packages are fetched from the location(s) specified in /etc/apt/sources.list
. For example, when using a Debian archive, this command retrieves and scans the Packages.gz
files, so that information about new and updated packages is available.upgrade
is used to install the newest versions of all packages currently installed on the system from the sources enumerated in /etc/apt/sources.list
. Packages currently installed with new versions available are retrieved and upgraded; under no circumstances are currently installed packages removed, or packages not already installed retrieved and installed. New versions of currently installed packages that cannot be upgraded without changing the install status of another package will be left at their current version.full-upgrade
(apt
) and dist-upgrade
(apt-get
), in addition to performing the function of upgrade
, also intelligently handles changing dependencies with new versions of packages; apt
and apt-get
have a "smart" conflict resolution system, and will attempt to upgrade the most important packages at the expense of less important ones if necessary. The /etc/apt/sources.list
file contains a list of locations from which to retrieve desired package files. [4] aptitude has a smarter dist-upgrade
feature called full-upgrade
. [11] /etc/apt
contains the APT configuration folders and files.
apt-config
is the APT Configuration Query program. [12] apt-config dump
shows the configuration. [13]
/etc/apt/sources.list
: [14] Locations to fetch packages from./etc/apt/sources.list.d/
: Additional source list fragments./etc/apt/apt.conf
: APT configuration file./etc/apt/apt.conf.d/
: APT configuration file fragments./etc/apt/preferences.d/
: Directory with version preferences files. This is where "pinning" is specified, i.e. a preference to get certain packages from a separate source or from a different version of a distribution./var/cache/apt/archives/
: Storage area for retrieved package files./var/cache/apt/archives/partial/
: Storage area for package files in transit./var/lib/apt/lists/
: Storage area for state information for each package resource specified in sources.list
/var/lib/apt/lists/partial/
: Storage area for state information in transit.APT relies on the concept of repositories in order to find software and resolve dependencies. For APT, a repository is a directory containing packages along with an index file. This can be specified as a networked or CD-ROM location. As of 14 August 2021, [update] the Debian project keeps a central repository of over 50,000 software packages ready for download and installation. [15]
Any number of additional repositories can be added to APT's sources.list configuration file (/etc/apt/sources.list
) and then be queried by APT. Graphical front ends often allow modifying sources.list
more simply (apt-setup
). Once a package repository has been specified (like during the system installation), packages in that repository can be installed without specifying a source and will be kept up-to-date automatically.
In addition to network repositories, compact discs and other storage media (USB keydrive, hard disks...) can be used as well, using apt-cdrom
[16] or adding file:/
URI [17] to the source list file. apt-cdrom
can specify a folder other than a CD-ROM, using the -d
option (i.e. a hard disk or a USB keydrive). The Debian CDs available for download contain Debian repositories. This allows non-networked machines to be upgraded. One can also use apt-zip
.
Problems may appear when several sources offer the same package(s). Systems that have such possibly conflicting sources can use APT pinning to control which sources should be preferred.
The APT pinning feature allows users to force APT to choose particular versions of packages which may be available in different versions from different repositories. This allows administrators to ensure that packages are not upgraded to versions which may conflict with other packages on the system, or that have not been sufficiently tested for unwelcome changes.
In order to do this, the pins in APT's preferences file (/etc/apt/preferences
) must be modified, [18] although graphical front ends often make pinning simpler.
Several other front ends to APT exist, which provide more advanced installation functions and more intuitive interfaces. These include:
APT front ends can:
APT front ends can list the dependencies of packages being installed or upgraded, ask the administrator if packages recommended or suggested by newly installed packages should be installed too, automatically install dependencies and perform other operations on the system such as removing obsolete files and packages.
The original effort that led to the apt-get
program was the dselect
replacement project known by its codename Deity. [24] This project was commissioned in 1997 by Brian White, the Debian release manager at the time. The first functional version of apt-get
was called dpkg-get
and was only intended to be a test program for the core library functions that would underpin the new user interface (UI). [25]
Much of the original development of APT was done on Internet relay chat (IRC), so records have been lost. The 'Deity creation team' mailing list archives include only the major highlights.
The 'Deity' name was abandoned as the official name for the project due to concerns over the religious nature of the name. The APT name was eventually decided after considerable internal and public discussion. Ultimately the name was proposed on IRC, accepted and then finalized on the mailing lists. [26]
APT was introduced in 1998 and original test builds were circulated on IRC. The first Debian version that included it was Debian 2.1, released on 9 March 1999. [27]
In the end the original goal of the Deity project of replacing the dselect
user interface was a failure. Work on the user interface portion of the project was abandoned (the user interface directories were removed from the concurrent versions system) after the first public release of apt-get
. The response to APT as a dselect
method and a command line utility was so great and positive that all development efforts focused on maintaining and improving the tool. It was not until much later that several independent people built user interfaces on top of libapt-pkg
.
Eventually, a new team picked up the project, began to build new features and released version 0.6 of APT which introduced the Secure APT feature, using strong cryptographic signing to authenticate the package repositories. [28]
APT was originally designed as a front end for dpkg to work with Debian's .deb
packages. A version of APT modified to also work with the RPM Package Manager system was released as APT-RPM. [29] The Fink project has ported APT to Mac OS X for some of its own package management tasks, [30] and APT is also available in OpenSolaris.
apt-file is a command, packaged separately from APT, to find which package includes a specific file, or to list all files included in a package on remote repositories. [31]
Debian, also known as Debian GNU/Linux, is a Linux distribution composed of free and open-source software and optionally non-free firmware or software developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993. The first version of Debian (0.01) was released on September 15, 1993, and its first stable version (1.1) was released on June 17, 1996. The Debian Stable branch is the most popular edition for personal computers and servers. Debian is also the basis for many other distributions that have different purposes, like Proxmox for servers, Ubuntu or Linux Mint for desktops, Kali for penetration testing, and Pardus and Astra for government use.
A Linux distribution is an operating system made from a software collection that includes the Linux kernel and often a package management system. They are often obtained from the website of each distribution, which are available for a wide variety of systems ranging from embedded devices and personal computers to servers and powerful supercomputers.
A package manager or package-management system is a collection of software tools that automates the process of installing, upgrading, configuring, and removing computer programs for a computer in a consistent manner.
dpkg is the software at the base of the package management system in the free operating system Debian and its numerous derivatives. dpkg
is used to install, remove, and provide information about .deb packages.
The Yellowdog Updater Modified (YUM) is a free and open-source command-line package-management utility for computers running the Linux operating system using the RPM Package Manager. Though YUM has a command-line interface, several other tools provide graphical user interfaces to YUM functionality.
deb is the format, as well as filename extension of the software package format for the Debian Linux distribution and its derivatives.
Synaptic is a GTK-based graphical user interface designed for the APT package manager used by the Debian Linux distribution and its derivatives. Synaptic is usually used on systems based on deb packages but can also be used on systems based on RPM packages. It can be used to install, remove and upgrade software packages and to add repositories.
Dependency hell is a colloquial term for the frustration of some software users who have installed software packages which have dependencies on specific versions of other software packages.
VectorLinux, abbreviated VL, was a Linux distribution for the x86 platform based on the Slackware Linux distribution, originally developed by Canadian developers Robert S. Lange and Darell Stavem. Since version 7 the Standard Edition is also available for the x86-64 platform, known as VLocity64 7.
debconf is a software utility for performing system-wide configuration tasks on Unix-like operating systems. It is developed for the Debian Linux distribution, and is closely integrated with Debian's package management system, dpkg.
dselect is a computer program used to manage software packages in the Debian operating system.
CNR, or One-Click & Run, was a free one-click software delivery service that was created to make finding and installing Linux software easier. It assisted the user in finding and installing software on their computer, and sat dormant in the system tray when not in use.
The Environment Modules system is a tool to help users manage their Unix or Linux shell environment, by allowing groups of related environment-variable settings to be made or removed dynamically.
Hildon is an application framework originally developed for mobile devices running the Linux operating system as well as the Symbian operating system. The Symbian variant of Hildon was discontinued with the cancellation of Series 90. It was developed by Nokia for the Maemo operating system. It focuses on providing a finger-friendly interface. It is primarily a set of GTK extensions that provide mobile-device–oriented functionality, but also provides a desktop environment that includes a task navigator for opening and switching between programs, a control panel for user settings, and status bar, task bar and home applets. It is standard on the Maemo platform used by the Nokia Internet Tablets and the Nokia N900 smartphone.
Ubiquity is the default installer for Ubuntu and its derivatives. It is run from the Live CD or USB and can be triggered to run from the options on the device or on the desktop of the Live mode. It was first introduced in Ubuntu 6.06 LTS "Dapper Drake". At program start, it allows the user to change the language to a local language if they prefer. It is designed to be easy to use.
Tiny Core Linux (TCL) is a minimal Linux kernel based operating system focusing on providing a base system using BusyBox and FLTK. It was developed by Robert Shingledecker, who was previously the lead developer of Damn Small Linux. The distribution is notable for its small size and minimalism; additional functions are provided by extensions. Tiny Core Linux is free and open-source software licensed under the GNU General Public License version 2.
Ubuntu Software Center, or simply Software Center, is a discontinued high-level graphical front end for the APT/dpkg package management system. It is free software written in Python, PyGTK/PyGObject based on GTK.
DebWrt is a discontinued, niche Linux distribution mainly installed on embedded systems. It was built on top of an OpenWrt base which was used to load a fully functional version of Debian from the RootFS stored on the attached USB storage device. For easy installation and deinstallation of packages it relied on the dpkg Package management system. DebWrt used the command-line interface of Bash. There was no web-based GUI interface.
Leafpad is a free and open-source graphical text editor for Linux, Berkeley Software Distribution (BSD), and Maemo that is similar to the Microsoft Windows program Notepad. Created with the focus of being a lightweight text editor with minimal dependencies, it is designed to be simple-to-use and easy-to-compile.
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: CS1 maint: postscript (link)gnome-apt was written by Havoc Pennington