APT Package Management

 

Table of Contents

Introduction. 1

Install a Package. 2

Remove a Package. 2

Finding a Package. 2

Software Updates. 3

Upgrade vs. Update. 3

List Installed Packages. 3

Other Packages to Install 3

Printing. 3

APT Directories and Files. 3

Repositories. 3

Package Database. 4

Package Cache. 4

 

 

Copyright © 2020 by Bruce Blinn

Introduction

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.

Install a Package

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 a Package

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

Finding a Package

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

Software Updates

Upgrade vs. Update

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

List Installed Packages

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

Other Packages to Install

apt-file                          Contains the apt-file command.

Printing

$ sudo apt install cups lpr

$ sudo service cups start

$ sudo service lpd start

 

lpadmin -p printer -E -v device -m ppd Lpadmin

APT Directories and Files

Repositories

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 ...

 

Type

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.

Package Database

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/.

Package Cache

The APT Package Cache is located in the directory /var/cache/apt/archives/.  It contains recently downloaded package files.