The Debian package management infrastructure is a simple yet powerful system that has been a distinguishing feature of Debian since the project's early years. At the core of the Debian package management is dpkg [1], a low-level tool used for installing and removing Debian .deb packages. The bigger and more comprehensive Advanced Package Tool (APT) [2] is a higher-level tool that includes dpkg on the back end. APT performs most of the other functions associated with a package management system, including integrating external repositories.

The APT package system supports a number of front-end applications, both command-line and GUI-based, that act as a user-friendly interface for managing Debian packages. In the past, most users who wanted to work at the command line depended on the classic apt-get tool as an interface to the Debian package system. Through the years, apt-get and a constellation of other supporting utilities, such as apt-cache, have provided nearly effortless package management for Debian users, as well as users of Debian-based distros like Ubuntu and Knoppix, who take the time to master the commands.

However, some users were not happy about the complex, and often confusing, system of apt-get commands and options. Since the release of Debian 8 "Jessie" and Ubuntu 16.04 "Xenial Xerus," all users of Debian-based systems can enjoy a new command-line interface to the APT system: apt. The apt utility consolidates features that were once spread among apt-get, apt-cache, and other commands, and it simplifies many of the command options for an easier and friendlier user experience.

The apt utility has been used in the Debian "Unstable" edition since 2014, and it became official with Debian 8. Because apt-get still works in recent releases of Debian and other Debian-based distros, many users have not taken the time to learn about apt. This article introduces the apt package management tool and explores some of the differences between apt and apt-get.

Note: The apt tool discussed in this article is not the same as the apt Python wrapper created by Linux Mint developers a few years ago.

apt vs apt-get

apt does not guarantee downwards-compatibility with apt-get, but many (though not all) command options are interchangeable. For a full comparison, type apt --help and apt-get --help and compare the results.

Table 1 shows some of the important commands side by side. As you can see, many commands are the same if you just exchange apt-get for apt. One exception is the apt upgrade command. The old command: apt-get upgrade installed the latest versions of all packages currently installed on the system from the repository, but it didn't remove existing packages or retroactively add dependencies. The new apt upgrade installs new packages when they are added as dependencies of packages to be updated, although it still doesn't remove previously installed packages.

The new command structure offers subtle improvements that save time and extra steps. For instance, apt-get lets you move a package to /var/cache/apt/archives/ and then install the package using apt-get install package_name, and the software automatically manages the dependencies. apt eliminates the need to push things around; all you need is apt install package_name, specifying the full path if necessary.

Design Error Corrected

apt fixes some errors of the original apt-get implementation. For example, in addition to apt-get for editing Debian packages, the legacy system used the apt-cache command for outputting information about the packages. The new apt command thoroughly cleans up, combining functions from both old commands and structuring them in a better way. apt provides features of the most commonly used apt-get and apt-cache commands, adding useful information that once required additional options.

For example, apt-get update only reports execution at the end (Figure 1), but apt update shows the number of updatable packages and offers an option to display a structured list of possible updates (Figure 2). This list even provides a better overview, adding color to the otherwise drab display (Figure 3).

Figure 1: Use apt-get update to update the lists using the packages provided by the repository, but do not expect to see any additional information.

Figure 2: The apt update command not only updates the package lists, but also shows you if and how many new versions of the packages exist in the repository.

Figure 3: Use apt list --upgradable to provide some color for a better overview of the packages for which the repository provides a more recent version.

The actual package update command has been given a new visual element: Both apt upgrade and apt full-upgrade or apt dist-upgrade now show a progress bar that informs users of the update progress (Figure 4).

Figure 4: apt full-upgrade uses a new element in the form of a progress bar to inform users about the upgrade's progress.

The update bar also appears when removing packages with apt remove or apt purge. apt remove removes the package itself, and apt purge removes the entire associated configuration – if it is located outside the home directory: apt never tampers with configurations in the user directory.

Two New Commands

The apt show command sorts the output alphabetically and suppresses some less important information that you might see with apt-cache show. The dist-upgrade parameter is assigned the more significant name of full-upgrade, although the two commands behave in the same way.

The apt list and apt edit-sources commands are new: apt list in connection with the --installed or --upgradeable options outputs lists of the installed or upgradeable packages; apt edit-sources <List> opens /etc/etc/apt/sources.list.d/ with the specified list in the editor for editing (Figure 5).

Figure 5: The apt tool opens the specified file for manual changes in the standard editor with the command apt edit-sources debian. list.