Ubuntu features a comprehensive package management system for installing, upgrading, configuring, and removing software. In addition to providing access to an organized base of over 60,000 software packages for your Ubuntu computer, the package management facilities also feature dependency resolution capabilities and software update checking.
Several tools are available for interacting with Ubuntu’s package management system, from simple command-line utilities that can be easily automated by system administrators, to an easy-to-use graphical interface for those new to Ubuntu.
Introduction
Ubuntu’s package management system is derived from the same system used by the Debian GNU/Linux distribution. The package files contain all of the necessary files, metadata, and instructions to implement a particular functionality or software application on your Ubuntu computer.
Debian package files typically have the extension .deb
, and usually exist in repositories which are collections of packages found online or on physical media, such as CD-ROM discs. Packages are normally in a pre-compiled binary format; thus installation is quick and requires no compiling of software.
Many packages use dependencies. Dependencies are additional packages required by the principal package in order to function properly. For example, the speech synthesis package festival
depends upon the package alsa-utils
, which is a package supplying the Advanced Linux Sound Architecture (ALSA) sound library tools needed for audio playback. In order for festival
to function, it – and all of its dependencies – must be installed. The software management tools in Ubuntu will do this automatically.
Advanced Packaging Tool – APT
The apt
command is a powerful command-line tool, which works with Ubuntu’s Advanced Packaging Tool (APT). The commands contained within apt
provide the means for installing new software packages, upgrading existing software packages, updating the package list index, and even upgrading the entire Ubuntu system.
Some examples of popular uses for the apt
utility include:
Install a Package
Installation of packages usingapt
is quite simple. For example, to install thenmap
network scanner, type the following:sudo apt install nmap
Tip
You can specify multiple packages to be installed or removed, by separating them with spaces.Remove a Package
Removal of a package (or packages) is also straightforward. To remove the package installed in the previous example, simply type:sudo apt remove nmap
Adding the
--purge
option toapt remove
will remove the package configuration files as well. This may or may not be the desired effect, so use with caution.Note:
Whileapt
is a command-line tool, it is intended to be used interactively, and not to be called from non-interactive scripts. Theapt-get
command should be used in scripts (perhaps with the--quiet
flag). For basic commands the syntax of the two tools is identical.Update the package index
The APT package index is essentially a database of available packages from the repositories defined in the/etc/apt/sources.list
file and in the/etc/apt/sources.list.d
directory. To update the local package index with the latest changes made in the repositories, type the following:sudo apt update
Upgrade packages
Installed packages on your computer may periodically have upgrades available from the package repositories (e.g., security updates). To upgrade your system, first, update your package index withsudo apt update
, and then type:sudo apt upgrade
For details on how to upgrade to a new Ubuntu release, see our guide on upgrading.
Actions of the apt
command, such as installation and removal of packages, are logged in the /var/log/dpkg.log
log file.
For further information about the use of APT, read the comprehensive APT User’s Guide, or type apt help
.
Aptitude
Launching Aptitude with no command-line options will give you a menu-driven, text-based frontend to the APT system. Many of the common package management functions, such as installation, removal, and upgrade, can be performed in Aptitude with single-key commands, which are typically lowercase letters.
Aptitude is best suited for use in a non-graphical terminal environment to ensure proper functioning of the command keys. You can start the menu-driven interface of Aptitude as a normal user by typing the following command at a terminal prompt:
sudo aptitude
When Aptitude starts, you will see a menu bar at the top of the screen and two panes below the menu bar. The top pane contains package categories, such as New Packages and Not Installed Packages. The bottom pane contains information related to the packages and package categories.
Using Aptitude for package management is relatively straightforward, and the user interface makes common tasks simple to perform. The following are examples of common package management functions as performed in Aptitude:
Install Packages
To install a package, locate it via the Not Installed Packages package category by using the keyboard arrow keys and the Enter key. Highlight the desired package, then press the + key. The package entry should turn green, indicating it has been marked for installation. Now press g to be presented with a summary of package actions. Press g again, and the package will be downloaded and installed. When finished, press Enter to return to the menu.Remove Packages
To remove a package, locate it in the Installed Packages package category by using the keyboard arrow keys and the Enter key. Highlight the package you want to remove, then press the - key. The package entry should turn pink, indicating it has been marked for removal. Now press g to be presented with a summary of package actions. Press g again, and the package will be removed. When finished, press Enter to return to the menu.Update Package Index
To update the package index, simply press the u key.Upgrade Packages
To upgrade packages, first update the package index as detailed above, and then press the U key to mark all packages with updates. Now press g, which will present you with a summary of package actions. Press g again to begin the download and installation. When finished, press Enter to return to the menu.
The first column of information displayed in the package list (in the top pane) lists the current state of the package (when viewing packages). It uses the following key to describe the package state:
i: Installed package
c: Package not installed, but package configuration remains on the system
p: Purged from system
v: Virtual package
B: Broken package
u: Unpacked files, but package not yet configured
C: Half-configured - configuration failed and requires fix
H: Half-installed - removal failed and requires a fix
To exit Aptitude, simply press the q key and confirm you wish to exit. Many other functions are available from the Aptitude menu by pressing the F10 key.
Command Line Aptitude
You can also use Aptitude as a command-line tool, similar to apt
. To install the nmap
package with all necessary dependencies (as in the apt
example), you would use the following command:
sudo aptitude install nmap
To remove the same package, you would use the command:
sudo aptitude remove nmap
Consult the Aptitude manpages for full details of Aptitude’s command-line options.
dpkg
dpkg
is a package manager for Debian-based systems. It can install, remove, and build packages, but unlike other package management systems, it cannot automatically download and install packages – or their dependencies. APT and Aptitude are newer, and layer additional features on top of dpkg
. This section covers using dpkg
to manage locally installed packages:
To list all packages in the system’s package database, installed and uninstalled, from a terminal prompt type:
dpkg -l
Depending on the number of packages on your system, this can generate a large amount of output. Pipe the output through
grep
to see if a specific package is installed:dpkg -l | grep apache2
Replace
apache2
with any package name, part of a package name, or a regular expression.To list the files installed by a package, in this case the
ufw
package, enter:dpkg -L ufw
If you are unsure which package installed a file,
dpkg -S
may be able to tell you. For example:See AlsoGrub - Debian Wikidpkg -S /etc/host.conf base-files: /etc/host.conf
The output shows that the
/etc/host.conf
belongs to the base-files package.Note:
Many files are automatically generated during the package install process, and even though they are on the filesystem,dpkg -S
may not know which package they belong to.You can install a local
.deb
file by entering:sudo dpkg -i zip_3.0-4_amd64.deb
Change
zip_3.0-4_amd64.deb
to the actual file name of the local.deb
file you wish to install.You can uninstall a package by:
sudo dpkg -r zip
Caution:
Uninstalling packages usingdpkg
, is NOT recommended in most cases. It is better to use a package manager that handles dependencies to ensure that the system is in a consistent state. For example, usingdpkg -r zip
will remove thezip
package, but any packages that depend on it will still be installed and may no longer function correctly.
For more dpkg
options see the manpage: man dpkg
.
APT configuration
Configuration of the APT system repositories is stored in the /etc/apt/sources.list
file and the /etc/apt/sources.list.d
directory. An example of this file is referenced here, along with information on adding or removing repository references from the file.
You can edit the file to enable and disable repositories. For example, to disable the requirement of inserting the Ubuntu CD-ROM whenever package operations occur, simply comment out the appropriate line for the CD-ROM, which appears at the top of the file:
# no more prompting for CD-ROM please# deb cdrom:[DISTRO-APT-CD-NAME - Release i386 (20111013.1)]/ DISTRO-SHORT-CODENAME main restricted
Extra repositories
In addition to the officially-supported package repositories available for Ubuntu, there are also community-maintained repositories which add thousands more packages for potential installation. Two of the most popular are the universe and multiverse repositories. These repositories are not officially supported by Ubuntu, but because they are maintained by the community they generally provide packages which are safe for use with your Ubuntu computer.
Note:
Packages in the multiverse repository often have licensing issues that prevent them from being distributed with a free operating system, and they may be illegal in your locality.
Warning:
Be advised that neither universe nor multiverse contain officially-supported packages. In particular, there may not be security updates for these packages.
Many other package sources are available – sometimes even offering only one package, as in the case of packages provided by the developer of a single application. You should always be very careful and cautious when using non-standard package sources/repos, however. Research the packages and their origins carefully before performing any installation, as some packages could render your system unstable or non-functional in some respects.
By default, the universe and multiverse repositories are enabled. If you would like to disable them, edit /etc/apt/sources.list
and comment out the following lines:
deb http://archive.ubuntu.com/ubuntu DISTRO-SHORT-CODENAME universe multiversedeb-src http://archive.ubuntu.com/ubuntu DISTRO-SHORT-CODENAME universe multiverse deb http://us.archive.ubuntu.com/ubuntu/ DISTRO-SHORT-CODENAME universedeb-src http://us.archive.ubuntu.com/ubuntu/ DISTRO-SHORT-CODENAME universedeb http://us.archive.ubuntu.com/ubuntu/ DISTRO-SHORT-CODENAME-updates universedeb-src http://us.archive.ubuntu.com/ubuntu/ DISTRO-SHORT-CODENAME-updates universe deb http://us.archive.ubuntu.com/ubuntu/ DISTRO-SHORT-CODENAME multiversedeb-src http://us.archive.ubuntu.com/ubuntu/ DISTRO-SHORT-CODENAME multiversedeb http://us.archive.ubuntu.com/ubuntu/ DISTRO-SHORT-CODENAME-updates multiversedeb-src http://us.archive.ubuntu.com/ubuntu/ DISTRO-SHORT-CODENAME-updates multiverse deb http://security.ubuntu.com/ubuntu DISTRO-SHORT-CODENAME-security universedeb-src http://security.ubuntu.com/ubuntu DISTRO-SHORT-CODENAME-security universedeb http://security.ubuntu.com/ubuntu DISTRO-SHORT-CODENAME-security multiversedeb-src http://security.ubuntu.com/ubuntu DISTRO-SHORT-CODENAME-security multiverse
Automatic updates
The unattended-upgrades
package can be used to automatically install updated packages and can be configured to update all packages or just install security updates. First, install the package by entering the following in a terminal:
sudo apt install unattended-upgrades
To configure unattended-upgrades
, edit /etc/apt/apt.conf.d/50unattended-upgrades
and adjust the following to fit your needs:
Unattended-Upgrade::Allowed-Origins { "${distro_id}:${distro_codename}"; "${distro_id}:${distro_codename}-security";// "${distro_id}:${distro_codename}-updates";// "${distro_id}:${distro_codename}-proposed";// "${distro_id}:${distro_codename}-backports";};
Certain packages can also be excluded and therefore will not be automatically updated. To block a package, add it to the list:
Unattended-Upgrade::Package-Blacklist {// "vim";// "libc6";// "libc6-dev";// "libc6-i686";};
Note:
The double “//” serve as comments, so whatever follows “//” will not be evaluated.
To enable automatic updates, edit /etc/apt/apt.conf.d/20auto-upgrades
and set the appropriate APT configuration options:
APT::Periodic::Update-Package-Lists "1";APT::Periodic::Download-Upgradeable-Packages "1";APT::Periodic::AutocleanInterval "7";APT::Periodic::Unattended-Upgrade "1";
The above configuration updates the package list, downloads, and installs available upgrades every day. These actions are triggered by timer units at a set time but with a random delay: apt-daily.timer
and apt-daily-upgrade.timer
. These timers activate the correspondent services that run the /usr/lib/apt/apt.systemd.daily
script.
However, it may happen that if the server is off at the time the timer unit elapses, the timer will be triggered immediately at the next startup. As a result, they will often run on system startup
and thereby cause immediate activity and hold the apt-lock.
In many cases this is beneficial, but in some cases it might be counter-productive; examples are administrators with many shut-down machines or VM images that are only started for some quick action, which is delayed or even blocked by the unattended upgrades. To adapt this behaviour, we can change/override the configuration of both APT’s timer units [apt-daily-upgrade.timer, apt-daily.timer
]. To do so, use systemctl edit <timer_unit>
and override the Persistent attribute, for example with Persistent=delay
:
[Timer]Persistent=delay
The local download archive is cleaned every week. On servers upgraded to newer versions of Ubuntu, depending on your responses, the file listed above may not be there. In this case, creating a new file of the same name should also work.
Note:
You can read more aboutapt
Periodic configuration options in theapt.conf(5)
manpage and in the/usr/lib/apt/apt.systemd.daily
script header.
The results of unattended-upgrades
will be logged to /var/log/unattended-upgrades
.
Notifications
Configuring Unattended-Upgrade::Mail
in /etc/apt/apt.conf.d/50unattended-upgrades
will enable unattended-upgrades
to email an administrator detailing any packages that need upgrading or have problems.
Another useful package is apticron
. apticron
will configure a cron job to email an administrator information about any packages on the system that have updates available, as well as a summary of changes in each package.
To install the apticron
package, enter the following command in a terminal:
sudo apt install apticron
Once the package is installed, edit /etc/apticron/apticron.conf
, to set the email address and other options:
EMAIL="[email protected]"
References
Most of the material covered in this chapter is available in man pages, many of which are available online.
The Installing Software Ubuntu wiki page has more information.
For more dpkg details see the dpkg man page.
The APT User’s Guide and apt man page contain useful information regarding APT usage.
For more info about systemd timer units (and systemd in general), visit the systemd man page and systemd.timer man page.
See the Aptitude user’s manual for more Aptitude options.
The Adding Repositories HOWTO (Ubuntu Wiki) page contains more details on adding repositories.
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