Table of Contents
Copyright © 2020 by Bruce Blinn
This tutorial assumes you are using a Ubuntu Linux system.
APT is an acronym for Advanced Package Tool.
A package is a collection of scripts, programs, files, and directories needed to install and run a program or application. If the package is dependent on another package, that information is also included in the package. A package may contain may contain an application in the form of source code or an executable file.
Packages primarily come in two different formats: RPM and dpkg. RPM was originally an acronym for Red Hat Package Manager, but it is now the recursive acronym for RPM Package Manager. RPM packages are used by Fedora and SUSE. The Debian package manager, dpkg, is used by Debian and Ubuntu.
The apt-get, apt-cache, and apt-config commands are low level commands for package management. They are built on the even lower level dpkg commnds. The apt command provides a more structured, high-level interface for the most commonly used options from these commands. Being a higher level interface, its usage is preferable when it will do the job.
Use the sudo command to run any commands that install or update the packages on the system.
If you want to install a package that is not supported by Ubuntu, you need to add the repository where it is located to the source.list file (see the section “Repositories” later in this document).
Before installing a package, you should update the local package database. Many system administrators use a cron script to update this database nightly, in which case, this step is not necessary.
$ sudo apt update
Install the package:
$ sudo apt install packageName
Remove the package:
$ sudo apt remove packageName
Removing a package does not remove configuration files for the package, which is useful if the package is reinstalled.
If the removed package was dependent upon another package that is no longer used, the output of the command will list that package as no longer needed, but it will not remove it.
If you want to remove a package, including its configuration files, use the apt purge command. You can also use this command after the apt remove command to remove the configuration files at a later time.
$ sudo apt purge packageName
You can use the apt autoremove command to remove packages that were automatically installed to satisfy a dependency but are no longer needed.
$ sudo apt autoremove
You can search for package names that match a pattern using the apt search command.
$ apt search pattern
Or, use the packages.ubuntu.com web page, which allows you to search packages using several criteria. For example, this utility enables you to find the package that contains a file or command.
You can find the package that contains a particular file using the apt-file command.
$ apt-file search filename
The apt update command updates the list of available packages and their versions, but it does not install or upgrade any packages. After running this command, APT has the information locally to determine whether the installed packages are the most recent version.
The apt upgrade command actually installs newer versions of the packages you already have.
To keep Ubuntu up to date, periodically execute the following commands. The –y option instructs the apt command to assume a yes response to most prompts.
$ sudo apt update
$ sudo apt upgrade –y
Run the apt list command to list Ubuntu Linux packages that are available.
$ apt list –-all_versions
To list the packages that are currently installed:
$ apt list –-installed
To list the packages that are currently installed and and the package name matches a pattern:
$ apt list –-installed pattern
apt-file Contains the apt-file command.
$ sudo apt install cups lpr
$ sudo service cups start
$ sudo service lpd start
lpadmin -p printer -E -v device -m ppd Lpadmin
Repositories are collections of packages available for download. They are usually on the installation CDROM or a server accessible via the Internet. Ubuntu maintains repositories for each of its supported releases.
The file /etc/apt/sources.list and the files in /etc/apt/sources.list.d/ contain the location and description of the repositories that are configured for use by the current system. That is, this is the list of repositories that the APT commands will search when you want to find or install a package.
In the sources.list file(s), each repository is listed on a separate line in the following format:
Type URI Repository Category ...
deb Packages contain executable files.
deb-src Packages contain source files.
URI Location of the repository (cdrom or an internet address).
Repository Name of the repository at that location.
Category Identifies the type of packages in the repository.
main Ubuntu supported open source software.
universe Community maintained open source software.
multiverse Software restricted by copyright.
restricted Proprietary device drivers.
extras Third party developed software.
partner Offered by vendors as service to Ubuntu users.
backports Packages from later releases of Ubuntu.
When making changes to the repositories, you should comment or uncomment entries in the sources.list file, or add new entries in files that you create in the sources.list.d directory. You can search for “Ubuntu repositories” on the Internet to find additional repositories.
The Package Database is a local database that contains the list of available packages and their versions. This information is created by reading each of the repositories configured for use on the system and recording information about each package that is available in each repository. The files that make up the package database are stored in the directory /var/lib/apt/lists/.
The APT Package Cache is located in the directory /var/cache/apt/archives/. It contains recently downloaded package files.