APT" stands for "Advanced Package Tool." APT is a package management system used by Debian and its derivatives, such as Ubuntu, to handle the installation, upgrade, and removal of software packages. It simplifies the process of managing software on Unix-like operating systems by automatically resolving dependencies, retrieving packages from repositories, and configuring the packages.
APT was designed to work with Debian's .deb packages, and it uses repositories where packages are stored, allowing users to search, install, or remove software easily. APT also has a command-line interface (apt-get, apt-cache) and other front-end tools like Synaptic Package Manager, which provides a graphical user interface for package management.
What does APT do?
APT is a set of core tools found inside the Debian operating system. It provides utilities for the installation and removal of software packages and dependencies on a system.
- APT is a powerful tool that can be used to manage software packages on Debian-based systems.
- APT can be used to install, remove, upgrade, and downgrade software packages.
- APT can also be used to manage dependencies between packages.
- APT is a valuable tool for any system administrator who needs to manage software packages on a Debian-based system.
apt-get / high level package handling utility
apt-getis the command-line tool for handling packages and provides functions such as installing, removing, and updating packages on a system with a single operation. We’ll cover the following commands forapt-get:
installand--reinstallremovepurgeor--purgeupgradeupdatecleanandautoclean
apt-cache / high level package query utlity
apt-cacheprovides an interface to perform read-only operations on the APT package cache.apt-cachedoes not change the state of the system, but allows the user to extract useful information from package metadata.
We’ll go over the following commands forapt-cache:
pkgnamessearchshow
dpkg / low level package manager for Debian
dpkgis a tool for installing, removing, and querying individual packages. We’ll investigate some common commands and go over some basic usage ofdpkgin a couple of real-world examples.
--listor-l--install--remove--purge--update--contents
apt-gethigh level package handling utility
Installing a Debian package:
$ sudo apt-get install [package-name]apt-getwants you to pass the[package-name]you wish to install, for example:
$ sudo apt-get install vimRemoving a Debian package:
The following will remove a packagewithoutremoving its configuration files:
$ sudo apt-get remove [package-name]To remove a packageandits configuration files, usepurge:
$ sudo apt-get purge [package-name]or alternatively, use the--purgeflag on the remove command:
$ sudo apt-get --purge remove [package-name]Update package index files from sources.list:
$ sudo apt-get updateWhen this command is run, all available packages are fetched and re-indexed from the locations specified in/etc/apt/sources.listand/etc/apt/sources.list.d/.
Upgrade all Debian system packages:
$ sudo apt-get upgradeThis command installsallof the latest versions of each package installed on the system and is, generally, not recommended to be run on production systems.
Update / Reinstall a single package:
Once you’ve runapt-get updateto update repository metadata, you can update an installed package by runningapt-get install
$ sudo apt-get install [package-name]If you need to force reinstall a package, just pass the--reinstallflag
$ sudo apt-get --reinstall install [package-name]By passing the--reinstallflag, you will effectively force the package to be reinstalled even if it’s already installed and at the latest version. This will completely remove the package from the system* and reinstall it.
*Packages that depend on the[package-name]being reinstalled will not be removed from the system
APT cache files:
APTs cached files are located in:
/var/cache/apt/archives/
Clear the APT cache:
$ sudo apt-get cleanThecleancommand clears out the local repository of downloaded package files. It removes everythingexceptthepartials folderandlock filefrom/var/cache/apt/archives/.
Useapt-get cleanto free up disk space when necessary, or as part of regularly scheduled maintenance.
Remove useless files from the APT cache:
$ sudo apt-get autocleanautocleanis another method used to clear out the local repository of downloaded package files, just likeclean. The difference betweencleanandautocleanis that the latter only removes package files that can no longer be downloaded from their sources, and are very likely to be useless.
apt-cachehigh level package query utility
List all available packages:
$ apt-cache pkgnamesThis command will output a list of available package names for your system:
...aspell-bg389-ds-console-doclibreoffice-l10n-galibindicate-doclibreadline-devlibpng12-devSearching for a specific Debian package:
$ apt-cache search [package-name-pattern]This is really useful in case you don’t know the exact[package-name], but rather a description of what that package does; for example “Network Security”:
$ apt-cache search "Network Security"This will return a list of packages containing the string “Network Security” in the package description. Using apt-cache will look in thename,description, andprovidesfields of the available packages by default.
libnss3 - Network Security Service librarieslibnss3-1d - Network Security Service librarieslibnss3-dbg - Debugging symbols for the Network Security Service librarieslibnss3-dev - Development files for the Network Security Service librariescoolkey - Smart Card PKCS #11 cryptographic moduledaemonlogger - simple network packet logger and soft tap daemongrepcidr - Filter IP addresses matching IPv4 CIDR/network specificationhlbrw - assistant to help make new rules to HLBRlibjss-java - Network Security Services for Javalibnss3-tools - Network Security Service toolslibopenvas2 - remote network security auditor - shared librarieslibopenvas2-dev - remote network security auditor - static libraries and headersopenvas-client - Remote network security auditor, the clientopenvas-plugins-base - remote network security auditor - basic pluginsopenvas-plugins-dfsg - remote network security auditor - pluginsopenvas-server - remote network security auditor - serveropenvas-server-dev - remote network security auditor - static libraries and headerspython-nss - Python bindings for Network Security Services (NSS)scute - OpenPGP smartcard plugin for Mozilla Network Security ServicesShow Debian package information:
$ apt-cache show [package-name]This will show apt metadata for the[package-name]given. This is an example using the “screen” package:
$ apt-cache show screenwill output:
Package: screenPriority: optionalSection: miscInstalled-Size: 1052Maintainer: Ubuntu Developers <[email protected]>Original-Maintainer: Jan Christoph Nordholz <[email protected]>Architecture: amd64Version: 4.0.3-14ubuntu8Depends: libc6 (>= 2.4), libncursesw5 (>= 5.6+20070908), libpam0g (>= 0.99.7.1), dpkg (>= 1.15.4) | install-info, upstart-jobSuggests: byobuFilename: pool/main/s/screen/screen_4.0.3-14ubuntu8_amd64.debSize: 611204MD5sum: b5e98bb56fdfc9bf9fd13e6f726c83aaSHA1: 8d3e5c5d858b4a314a66b5bc51b3a557b85ea96cSHA256: 2b6c752fc226ad6e2e32cd93f089bf2a89d51e95f6e5ff1e7ed63b0b57ff592fDescription-en: terminal multiplexor with VT100/ANSI terminal emulation screen is a terminal multiplexor that runs several separate "screens" on a single physical character-based terminal. Each virtual terminal emulates a DEC VT100 plus several ANSI X3.64 and ISO 2022 functions. Screen sessions can be detached and resumed later on a different terminal. . Screen also supports a whole slew of other features. Some of these are: configurable input and output translation, serial port support, configurable logging, multi-user support, and utf8 charset support.Homepage: http://savannah.gnu.org/projects/screenDescription-md5: 031a852784c43a4c757fecf6b610c93eBugs: https://bugs.launchpad.net/ubuntu/+filebugOrigin: UbuntuSupported: 5yTask: cloud-image, ubuntu-usb, server, edubuntu-usb, edubuntu-desktop-kde, edubuntu-desktop-gnomeNOTE: Installed-Size and Size are returned in bytes -link to discussion
dpkglow level package manager for Debian
Install a package:
dpkg -i [/path/to/vim_7.3.429-2ubuntu2_amd64.deb]or alternatively, use the--installflag
dpkg --install [/path/to/vim_7.3.429-2ubuntu2_amd64.deb]Remove a package:
To remove a package usingdpkgwithoutremoving its configuration files:
$ dpkg --remove [package-name]alternatively, use the-rflag:
$ dpkg -r [package-name]To remove a package usingdpkgalong withits corresponding configuration files, use the--purgecommand:
$ dpkg --purge [package-name]List available system packages:
dpkg -lallows you to list a set of packages on the system and the state of those packages:
$ dpkg -l [package-name-pattern]You can use a regular expression to list information about all matching package names. For example:
$ dpkg -l "re*"will return all packages starting with the letters “re”:
||/ Name Version Description+++-==========================-==========================-====================================================================un readahead <none> (no description available)ii readline-common 6.2-8 GNU readline and history libraries, common filesun rebuildd <none> (no description available)un redhat-cluster-modules <none> (no description available)ii redis 2.8.3-1 redisun regina-normal-dev <none> (no description available)ii reprepro 4.8.2-1ubuntu0.1 Debian package repository producerii resolvconf 1.63ubuntu15 name server information handlerThe first column shows the state of the package. You can learn more about package states by reading the dpkg man page:man 1 dpkg.
If the[package-name-pattern]is omitted fromdpkg -lthen all packages in/var/lib/dpkg/statuswill be listed, excluding packages that have been marked not-installed
$ dpkg -lwill output something like:
...ii libxml2 2.7.8.dfsg-5.1ubuntu4.11 GNOME XML libraryii libxml2-dbg 2.7.8.dfsg-5.1ubuntu4.11 Debugging symbols for the GNOME XML libraryii libxml2-dev 2.7.8.dfsg-5.1ubuntu4.11 Development files for the GNOME XML libraryii libxmuu1 2:1.1.0-3 X11 miscellaneous micro-utility libraryii libxrender1 1:0.9.6-2ubuntu0.1 X Rendering Extension client libraryii libxslt1-dev 1.1.26-8ubuntu1.3 XSLT 1.0 processing library - development kitii libxslt1.1 1.1.26-8ubuntu1.3 XSLT 1.0 processing library - runtime libraryii libyaml-0-2 0.1.4-2 Fast YAML 1.1 parser and emitter libraryii libyaml-dev 0.1.4-2 Fast YAML 1.1 parser and emitter library (development)ii linux-firmware 1.79 Firmware for Linux kernel driversii linux-image-3.2.0-29-virtu 3.2.0-29.46 Linux kernel image for version 3.2.0 on 64 bit x86 Virtual Guestsii linux-image-virtual 3.2.0.29.31 Linux kernel image for virtual machinesii linux-libc-dev 3.2.0-37.58 Linux Kernel Headers for development...List files in a package:
dpkg maintains a list of packages that are installed on a system in/var/lib/dpkg.
You can query the files in an installed package usingdpkg -L:
$ dpkg -L [package-name]So, for example:
$ dpkg -L redisreturns the following results:
/./usr/usr/share/usr/share/doc/usr/share/doc/redis/usr/share/doc/redis/copyright/usr/share/doc/redis/changelog.Debian.gz/usr/bin/usr/bin/redis-check-dump/usr/bin/redis-benchmark/usr/bin/redis-server/usr/bin/redis-check-aof/usr/bin/redis-cliIf you’d like to list the files in a debian package that you’ve downloaded (but not installed), you can use the--contentsflag.
For example:
$ dpkg --contents /path/to/redis_2.8.3-1_amd64.debreturns the following results:
drwxr-xr-x root/root 0 2014-07-24 09:52 ./drwxr-xr-x root/root 0 2014-07-24 09:52 ./usr/drwxr-xr-x root/root 0 2014-07-24 09:52 ./usr/share/drwxr-xr-x root/root 0 2014-07-24 09:52 ./usr/share/doc/drwxr-xr-x root/root 0 2014-07-24 09:52 ./usr/share/doc/redis/-rw-r--r-- root/root 0 2014-07-24 09:52 ./usr/share/doc/redis/copyright-rw-r--r-- root/root 139 2014-07-24 09:52 ./usr/share/doc/redis/changelog.Debian.gzdrwxr-xr-x root/root 0 2014-07-24 09:52 ./usr/bin/-rwxr-xr-x root/root 22616 2014-07-24 09:52 ./usr/bin/redis-check-dump-rwxr-xr-x root/root 285712 2014-07-24 09:52 ./usr/bin/redis-benchmark-rwxr-xr-x root/root 844496 2014-07-24 09:52 ./usr/bin/redis-server-rwxr-xr-x root/root 10320 2014-07-24 09:52 ./usr/bin/redis-check-aof-rwxr-xr-x root/root 320432 2014-07-24 09:52 ./usr/bin/redis-cliWhen the--contentsflag is used,dpkgcalls down to an action provided by another tooldpkg-deb, which provides tools to manipulate a debian package archive.
Show packages containing a filename or filepath:
$ dpkg -S [filename-search-pattern]For example, passing a specific filepath:
$ dpkg -S /usr/share/man/man5will return all the package names that contain that file path.
libc-bin, libarchive-dev, ntp, libpam-modules, libpam-runtime, initscripts, upstart, mount,libx11-data, fontconfig-config, isc-dhcp-client, isc-dhcp-common, rsyslog, sudo, ucf,collectd-core, libwrap0, openssl, openssh-client, rsync, module-init-tools, ncurses-bin,procps, login, nfs-common, cryptsetup, git-man, man-db, cron, libmagic1, libldap-2.4-2,libtirpc1, libnfsidmap2, adduser, resolvconf, dpkg, e2fsprogs, ifupdown, initramfs-tools,locales, kbd, openssh-server, apt, wireless-regdb, util-linux, passwd, mime-support, net-tools,manpages, dpkg-dev: /usr/share/man/man5Show package information:
You can show package metadata of installed packages by usingdpkg -s:
$ dpkg -s [package-name]for example, the following command:
$ dpkg -s screenreturns the package metadata:
Package: screenStatus: install ok installedPriority: optionalSection: miscInstalled-Size: 1052Maintainer: Ubuntu Developers <[email protected]>Architecture: amd64Version: 4.0.3-14ubuntu8Depends: libc6 (>= 2.4), libncursesw5 (>= 5.6+20070908), libpam0g (>= 0.99.7.1), dpkg (>= 1.15.4) | install-info, upstart-jobSuggests: byobuConffiles: /etc/screenrc 12c245238eb8b653625bba27dc81df6a /etc/init/screen-cleanup.conf 441f4a1c5b41d7f23427be5aa6ccbbccDescription: terminal multiplexor with VT100/ANSI terminal emulation screen is a terminal multiplexor that runs several separate "screens" on a single physical character-based terminal. Each virtual terminal emulates a DEC VT100 plus several ANSI X3.64 and ISO 2022 functions. Screen sessions can be detached and resumed later on a different terminal. . Screen also supports a whole slew of other features. Some of these are: configurable input and output translation, serial port support, configurable logging, multi-user support, and utf8 charset support.Homepage: http://savannah.gnu.org/projects/screenOriginal-Maintainer: Jan Christoph Nordholz <[email protected]>Here are some additional tips for using APT and its related tools:
Use the
apt-cache showcommand to view information about a package, such as its version, description, and dependencies.Use the
apt-cache searchcommand to search for packages by name or keyword.Use the
apt-get installcommand to install a package.Use the
apt-get removecommand to remove a package.Use the
apt-get updatecommand to update the list of available packages.Use the
apt-get upgradecommand to upgrade all installed packages to the latest version.Use the
apt-get dist-upgradecommand to upgrade all installed packages, including removing and installing packages as needed.Use the
apt-get autoremovecommand to remove packages that are no longer needed.Use the
apt-get cleancommand to remove downloaded package files.Use the
apt-get autocleancommand to remove downloaded package files that are no longer needed.
Conclusion
Getting more familiar with your package manager’s tools can help you be more productive when finding, installing, and querying packages.apt-get,apt-cache, anddpkg.You can learn more about the tools mentioned in this blog post by reading the man pages as well.
