Debian

Introduction to Debian Package Management

Ubuntu and all other Debian Linux distributions offer a comprehensive set of package management systems that provides access to an organized database of over 6000 packages. The package management facilitates the task of package installation, configuration, upgrade, and removal. It also resolves the process of dependency-related issues by including the dependency resolution features.

The Debian package management offers several tools including, dpkg, Advanced Packaging Tool (APT), and aptitude utility to perform package management tasks. This tutorial uses each of these Debian Management tools to describe:

  • How to install, remove, reinstall, and upgrade Debian packages?
  • How to find files or libraries of uninstalled packages?
  • How to obtain package metadata or version and content details when the package is uninstalled?

Background

In the earliest Linux systems, packages were installed or added by grabbing the source code from the project built it. The users then compiled the source code into runnable binaries, including manual pages, libraries, and configuration files to create a required program. The user may find the programs already compiled by someone to add to the system in a better scenario.

The compiled program was the tarball: a single file containing multiple files gathered for convenient distribution. In other words, after installation from a tarball, files spread across the Linux system in various appropriate folders and subdirectories such as /etc., /bin, /var, /usr/share/man, etc.

Even though it’s easy to create a tarball, it has some issues such as:

  • Tracking down required dependencies
  • The user is not aware of configuration files and documentation located in the system. It further complicates the process of software removal.
  • Tarballs do not contain software metadata, making it difficult to fix bugs and update to a new version.

To resolve these problems, Linux introduced a complex system for package management dividing all the Linux distributions into incorporating one of the two major packaging formats known as DEB and RPM. The article focuses on the Debian-based-package management system used by Debian and derivatives of Debian distribution such as Ubuntu, Linux Mint, etc.

Before moving onwards with the demonstration of various package management tasks, let’s first explain what the Debian package file is and how all the above discussed Debian package managers differ from each other.

.deb File

A file with a .deb extension contains the content of a Debian package
software. The Deb file further consists of two Tar files that make up the executables, libraries, and other files.

The general syntax of any Debian package file is as follows:

<package-name>_<version>.<revision>-<debian_codename>_<architecture>.deb

For instance, apache_1.3.31-6_i386.deb tells the base name of software to be apache. 1.3.31-6 is the version number assigned by the packager. Lastly, i386 implies that the package is compiled for Intel x86 architecture.

Besides, any file with the .deb extension is downloadable via the dpkg command and represents a complete file name. At the same time, only the package name apache refers to the first part of the .deb file.

Debian Package Managers

The DPM consists of several layers, as the top layer constitutes commands from the apt family of tools, and the lower layer is of dpkg and associated tools.

dpkg

dpkg is a Debian package manager that installs, removes, and configures packages with the .deb extension. It simply downloads DEB package content to the system and notifies about the required dependencies. But it does not install or configure .deb packages due to missing dependencies as it does not have access to the repositories.

APT

APT is a powerful command-line tool that manages the installation and configuration of deb packages. It further manages and downloads the necessary dependencies to provide the latest software. It works as a front-end for dpkg: after listing all the dependencies and downloading from the repository.

Hence, APT automates the problem in dpkg. It further compares the dependencies and informs the users about the one’s not in use by any package that a user can remove.

Package Location

The package installation from any Debian Software center or command-line utilities (apt/apt-get) happens via downloading packages from one or more repositories. A Debian or APT repository is a server or a local directory containing packages files and their metadata readable by the APT tools.

Hence, on all the Debian-based distributions, the APT Package management system maintains repositories inside the main configuration file /etc/apt/sources.list. So whenever a user executes a command for package installation, the apt/apt-get command looks inside the /etc/apt/sources.list or /etc/apt/sources.list.d for repository URLs.

It then downloads the desired software for installation. The source.list file further contains additional information about the repositories for the software to install. The user can manually add new repositories in the /etc/apt/sources.list.d directory without editing the main configuration file. However, the names of the new repository files must follow the /etc/apt/source.list format. cat the content of the /etc/apt/sources.list file:

[email protected]:~$ sudo cat /etc/apt/sources.list | less

The general syntax for each included repository is as follows:

deb http://repo.tld/ubuntu distro component
deb-src http://us.archive.ubuntu.com/ubuntu/ saucy-updates universe
  • deb: represents the deb archive. It can either be deb that implies .deb package or deb-src repositories containing package source code.
  • http: //repo.tld/ubuntu: repository URL
  • distro: distribution code name
  • component: it’s the repository categories. For instance, the default Ubuntu repositories have four categories: main, restricted, multiverse, and universe.

The APT and other tools use a local database to determine installed packages. To maintain the local database, synchronize the information with the repositories listed in the sources.list using the apt-get update command. Hence, it’s necessary to perform a local database update before each package installation or update.

Aptitude

Aptitude is a menu-driven, text-based interface for dpkg and Advanced Packaging Tool package management functions. It’s best suited for a non-graphical interface environment that makes user tasks easy to perform. It uses apt-get libraries and provides more perks due to an interactive UI.

Debian Package Installation

Linux installation automatically installs a set of packages that a user can further customize as per the use of the system, i.e., desktop, server, or workstation. A user also sometimes requires to install new packages. Let’s discuss package installation concerning the above-discussed package managers.

Installation via APT-GET

Use the apt-get install command to install the package with a list of extra packages. The below screenshot displays the list of dependencies and prompts for continuation.

[email protected]:~$ sudo apt-get install tmux

As shown below, after download the command-line tool also unpacks the libutempter0_1.1.6-3_amd64.deb package.

Preparing to unpack .../libutempter0_1.1.6-3_amd64.deb ...
Unpacking libutempter0:amd64 (1.1.6-3) ...

Instead of installation, the -s flag only figures out if the package depends on other packages.

[email protected]:~$ sudo apt-get install -s tmux
..<SNIP>...
The following additional packages will be installed:
  libutempter0
..<SNIP>...

Installation via dpkg

In case you get to download a .deb file with all the dependencies, without apt-get. Use the following command to install it via dpkg.

[email protected]u:~$ sudo dpkg -i <packagename>.deb

Installation via Aptitude

Run aptitude via a terminal with sudo privileges.

[email protected]:~$ sudo aptitude

Use the Ctrl+T key combination to enter the main aptitude menu. But before that, use the arrow keys to enter the submenu of aptitude ‘Not Installed Packages‘ section. It shows several sub-menus, choose net and scroll down to its submenu to select main to reveal all applications. Choose your desired application and hit Enter to see all the package details.

Mark the application for installation by pressing the ‘+‘ key and hit the ‘g‘ key to begin the installation. During installation, aptitude will be in console mode; once done, it returns to the user interface with a display of a complete package description.

Debian Package Removal

The section elaborates on the Debian package removal process. Let’s discuss the package removal process via each package manager.

Removing Package via APT

The remove option of an apt-get command only removes all the package data.

[email protected]:~$ sudo apt-get remove tmux

That is, all the configuration files are left behind. Hence, if the command gets executed accidentally, issue an installation command for the removed package to restore its function. To remove all the configuration files, as well use the purge option.

[email protected]:~$ sudo apt-get purge tmux

Besides, the output in the screenshot above depicts that the unrequired dependencies are not removed. For this purpose, the –auto-remove option does the job for us.

[email protected]:~$ sudo apt-get --auto-remove tmux

Combine the purge and –auto-remove options to completely delete all the data and files along with unrequired dependencies.

[email protected]:~$ sudo apt-get purge --auto-remove tmux

Removing Packages via dpkg

The package removal process in dpkg is almost similar. Use dpkg -r to remove the package data and dpkg -P to completely delete the package. First, list the package to ensure if it’s correctly installed in the system.

[email protected]:~$ dpkg -l | grep tmux
[email protected]:~$ sudo dpkg -r tmux
[email protected]:~$ sudo dpkg -P tmux

dpkg further allows forcefully deleting the files in a scenario of distribution upgrade that requires the user to delete or remove a package. But sometimes, the remove option doesn’t work due to the package’s unmet dependencies or incomplete installation. For that, dpkg offers forced package removal:

[email protected]:~$ sudo dpkg --force-all --remove tmux

Removing Packages via Aptitude

Uninstallation via aptitude is as simple as the installation. Scroll down and select ‘Installed Packages’ to view all installed programs. Select net->main and choose the program by pressing a ‘’ key. Press ‘g’ to remove the selected package.

Debian Package Update

To update a single package, use the apt-get command with the install option. It also upgrades the extra packages or dependencies. However, it’s necessary to ensure that the local databases reflect the latest updates:

[email protected]:~$ sudo apt-get update
[email protected]:~$ sudo apt-get install vim

Instead of updating the packages individually, it’s better to update all the applications in the system, as follows:

[email protected]:~$ sudo apt-get update
[email protected]:~$ sudo apt-get upgrade

Finding Uninstalled Debian Package Information

All the package management tools are aware of the available packages a user may need to install. The apt-cache is one such command that maintains a repository containing information about packages from the source list. It enables the user to retrieve the information about the packages in apt’s cache.

For instance, to install a package relevant to a chatting program with no knowledge of the package name, a user can use the following command:

[email protected]:~$ sudo apt-cache search chat

The above command will return a list of packages available for a chat application.

Similarly, a lot of tools are available to find packages from an already available list of packages. Users can find a lot of detail about the installed package with them but not for an uninstalled one, for instance, files inside an uninstalled package. For this purpose, use the -d option with an apt-get command, as it only downloads the package.

[email protected]:~$ sudo apt-get install -d python3

The downloaded package file is located inside /var/cache/apt/archives/ directory. Now use the dpkg command with the –info option to display package details or the –contents option to display package files.

[email protected]:~$ dpkg --info /var/cache/apt/archives/nmap_7.60-1ubuntu5_amd64.deb|less
[email protected]:~$ dpkg --contents /var/cache/apt/archives/nmap_7.60-1ubuntu5_amd64.deb|less

Finding Installed Debian Packages Information

The dpkg tool makes use of many files available in the /var/lib/dpkg directory. One of them is the /var/lib/dpkg/status file that contains package status information. The use of a dpkg command with the -s option displays the status of the packages on the system.

[email protected]:~$ sudo dpkg -s vim

dpkg also enables Linux users to find details of a particular package and a file belonging to a specific package. The dpkg tool -L option lists all the files and directories of the package of interest. All dpkg requires is a package name, but when multiple versions of an application are available, it requires a more detailed name containing version details.

[email protected]:~$ dpkg -L vim

To find a package containing a specific file, use the -S flag. For instance, use the following command to figure out which package contains the file /usr/bin/apt-get.

[email protected]:~$ dpkg -S /usr/bin/apt-get

Lastly, we can find details or purpose of a particular package as follows:

[email protected]:~$ dpkg -p vim

Conclusion

The article provides a detailed description of Debian’s package management. It discusses various ways to install, remove, update or upgrade packages. We also learned how to find package status and many other details about uninstalled Debian packages. The article is a one-stop guide covering every aspect of package management in Ubuntu or any Debian Distribution. Thank you for coming this far; you can place your queries in the comment section below. For details on package management in RHEL distributions, read Introduction to RPM/YUM package management.

About the author

Usama Azad

A security enthusiast who loves Terminal and Open Source. My area of expertise is Python, Linux (Debian), Bash, Penetration testing, and Firewalls. I’m born and raised in Wazirabad, Pakistan and currently doing Undergraduation from National University of Science and Technology (NUST). On Twitter i go by @UsamaAzad14