[HowTo] Using apt from the command line interface

[Hallvor]

Skill level: Beginner

The apt command-line interface is a powerful tool that enables users to search for packages, install or remove them, and upgrade the system. This how-to guide will explain how to use the apt package manager in Debian without needing GUI package managers like Synaptic or Discover.

Since apt can do system-wide changes, it needs root or sudo privileges. If your system has root or sudo enabled depends if you set a root password during installation. If you set a root password, you can use root. If you didn't set one, you must use sudo.

Open a terminal with Ctrl + Alt + T.

You should then get a command prompt like this:

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hallvor@debian:~$

Using root

You can switch from user to root by typing in the following command and pressing enter. Notice the - after su.

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hallvor@debian:~$ su -

After the successful entry of a root password, you will change from user to root:

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root@debian:~#

In order to use sudo, just type sudo before your command, like this to update the package lists:

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hallvor@debian:~$ sudo apt update

In this scenario, you type in your user's password. Keep in mind that sudo privileges last for 15 minutes after running a sudo command. This means that if you run a command with sudo, you should not be prompted for a password again for the next 15 minutes when running subsequent sudo commands.

In this howto, we'll use root (#) for the examples.

In order to edit your sources.list, you can use the apt edit-sources-command

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# apt edit-sources

Then select the editor, edit the file and save and exit. To exit nano, you can press "Ctrl + X".
To exit and save in Vim:
Press "Esc" to enter command mode. Type ":wq" to write the file out to disk and quit vim. Press "Enter" to execute the command.


Update the package lists

It is always a good idea to update the package lists before installing anything to ensure that you have the latest package information. If you have edited your sources.list

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# apt update

Install upgrades

If there are any updates, you can install them with

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# apt upgrade

Search for an application

We can search for an application with the search command. In order to search for the multimedia player VLC, we can use this command:

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# apt search vlc

Apt will provide a list of plugins and related packages.

Some searches will give too many results, resulting in output that is only partial. One solution is to pipe the output into less:

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# apt search vlc | less

This will display the search results for vlc in a pager, allowing you to view the output one page at a time. You can navigate through the output by using the PgUp and PgDn keys on your keyboard.

To exit less, you can press the q key.


Show information about a package

The show-command will give extensive information about a given package, including its dependencies, installation and download size.

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# apt show vlc

Package: vlc
Version: 3.0.18-0+deb11u1
Priority: optional
Section: video
Maintainer: Debian Multimedia Maintainers <debian-multimedia@lists.debian.org>
Installed-Size: 237 kB
Provides: mp3-decoder
Depends: vlc-bin (= 3.0.18-0+deb11u1), vlc-plugin-base (= 3.0.18-0+deb11u1), vlc-plugin-qt (= 3.0.18-0+deb11u1), vlc-plugin-video-output (= 3.0.18-0+deb11u1)
Recommends: vlc-l10n (= 3.0.18-0+deb11u1), vlc-plugin-access-extra (= 3.0.18-0+deb11u1), vlc-plugin-notify (= 3.0.18-0+deb11u1), vlc-plugin-samba (= 3.0.18-0+deb11u1), vlc-plugin-skins2 (= 3.0.18-0+deb11u1), vlc-plugin-video-splitter (= 3.0.18-0+deb11u1), vlc-plugin-visualization (= 3.0.18-0+deb11u1)
Suggests: vlc-plugin-fluidsynth (= 3.0.18-0+deb11u1), vlc-plugin-jack (= 3.0.18-0+deb11u1), vlc-plugin-svg (= 3.0.18-0+deb11u1)
Homepage: https://www.videolan.org/vlc/
Tag: hardware::storage, hardware::storage:cd, hardware::storage:dvd,
 hardware::video, implemented-in::c, implemented-in::c++,
 interface::commandline, interface::graphical, interface::x11,
 protocol::ipv6, protocol::ssl, role::program, scope::application,
 scope::utility, sound::compression, sound::player, uitoolkit::ncurses,
 uitoolkit::qt, use::converting, use::playing, works-with-format::TODO,
 works-with-format::mp3, works-with-format::oggtheora,
 works-with-format::oggvorbis, works-with-format::wav, works-with::TODO,
 works-with::audio, works-with::video, x11::application
Download-Size: 146 kB
APT-Manual-Installed: yes
APT-Sources: http://deb.debian.org/debian bullseye/main amd64 Packages
Description: multimedia player and streamer
 VLC is the VideoLAN project's media player. It plays MPEG, MPEG-2, MPEG-4,
 DivX, MOV, WMV, QuickTime, WebM, FLAC, MP3, Ogg/Vorbis files, DVDs, VCDs,
 podcasts, and multimedia streams from various network sources.
 .
 VLC can also be used as a streaming server that duplicates the stream it
 reads and multicasts them through the network to other clients, or serves
 them through HTTP.
 .
 VLC has support for on-the-fly transcoding of audio and video formats, either
 for broadcasting purposes or for movie format transformations. Support for
 most output methods is provided by this package, but features can be added by
 installing additional plugins:
  * vlc-plugin-access-extra
  * vlc-plugin-fluidsynth
  * vlc-plugin-jack
  * vlc-plugin-notify
  * vlc-plugin-samba
  * vlc-plugin-skins2
  * vlc-plugin-svg
  * vlc-plugin-video-splitter
  * vlc-plugin-visualization

Installing an application

In order to install an application, we can use the apt install command. In order to install vlc and international translations, we can issue the following command:

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# apt install vlc vlc-l10n

Notice that you can install several packages as long as you have space between them.


Removing an application

In order to remove an application, we can use the apt remove command, for instance like this:

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# apt remove vlc vlc-l10n

A word of caution: Please don't blindly confirm removal of packages. A single package can be part of a larger metapackage, so if you remove a package, the system will ask you to remove all the packages within that metapackage. This may give you a broken system.


Purging an application

In Debian, the purge command is used to completely remove an application along with its configuration files. This means that if you reinstall the program at a later time, it will be installed with its default settings.

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# apt purge vlc

Removing the configuration files may be a good idea if the application isn't working as expected.


View the apt log entries

Apt logs are located in /var/log/apt/history.log. We can view them conveniently with less:

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# less /var/log/apt/history.log

Saving a list of all your installed packages

You can use apt to save a list of all your installed packages.

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# apt list --installed > packages.txt

The list is saved to a file called packages.txt, and you can view the content of the package with

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# nano packages.txt

As mentioned, apt is a powerful tool that lets you set up your sources.list, view, install, remove, purge and save lists of your installed packages. I hope this was useful.



Edits:
10.04.23: Edited default directory after changing to root account. Thanks to itmicp for pointing it out. Added info about piping search results into less. Thanks to CynicalDebian.
11.04.23: Added location of apt's log. Thanks to CwF.

[CynicalDebian]

Nice guide! But apt search sometimes gives unusable output because of how long it is, perhaps add a section on piping into less and scrolling up with PG UP and PG DN? New users of apt may not be familiar with terminal pagers.

[Hallvor]

Added. Thanks!

[CwF]

Don't forget 'scrollback'

Pagers lock the user into its way, if using a terminal like xfce4-terminal there is the scrollback setting I've set to 1000 lines, and use it. There is also the 'unlimited' setting!

I thought there is a apt history log also for review, and maybe capture the operation in 'script' piped to file to create your own history.

[itmicp]

Hi

This is not an apt command line
but just a way I use the apt log files.

To see the list of packages I asked to install without listing the ones installed during the system installation,
I run the following command line:

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zgrep -h 'Commandline: apt install' /var/log/apt/history.log{,.[0-9]*.gz} | sed ':a;N;$!ba;s/\n\|Commandline: apt install/ /g; s/\( \)*/\1/g;s/ -y / /;'

But I should also take into account the packages that have been uninstalled…

[kent_dorfman766]

<CTRL><ALT><T>?

What is this witchcraft? I think thee is in league with Lucifer, or at least with his minions: Gnome.

[Hallvor]

<CTRL><ALT><T>?

What is this witchcraft? I think thee is in league with Lucifer, or at least with his minions: Gnome.