How to use apt

apt is a package manager for Debian-based systems. It is used to install, update, and remove software packages.

Use for C\C++

By defualt, your C program #include will import files under /usr/include. And your C++ program #include will import files under /usr/include/c++/version.

For example, if I want to build a program which should call curl, I need to install libcurl4-openssl-dev.

sudo apt install libcurl4-openssl-dev

Then I can build a new C file check_website.c:

#include <stdio.h>
#include <curl/curl.h>

int main(void) {
    CURL *curl;
    CURLcode res;
    long http_code = 0;

    curl_global_init(CURL_GLOBAL_DEFAULT);
    curl = curl_easy_init();

    if(curl) {
        curl_easy_setopt(curl, CURLOPT_URL, "https://www.google.com");
        curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);

        res = curl_easy_perform(curl);

        if(res != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        } else {
            curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_code);
            printf("Response code: %ld\n", http_code);
        }

        curl_easy_cleanup(curl);
    }

    curl_global_cleanup();
    return 0;
}

After installing libcurl4-openssl-dev gcc build-essential, I can build the program with:

gcc ./check_website.c -o check_website -lcurl

Then I can run the program with:

./check_website
200

As you can see, the program will print 200 which means the website is OK.

C\C++ program is very happy to use apt to install the dependencies.

Basic usages

Right here covers basic daily usages of apt. Including:

  • Install a package
  • Uninstall a package
  • Upgrade all installed packages
  • Search new packages
  • List all installed packages

Install

To install a new package, use the install command followed by the package name.

sudo apt install package-name

Example:

sudo apt install git

Remove

apt remove will only remove one package. It will not remove any packages that were installed as dependencies.

For example, some packages were automatically installed and are no longer required. apt remove will not remove them.

anduin@host $ sudo apt remove git
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages were automatically installed and are no longer required:
  bup-doc git-man liberror-perl python3-distupgrade python3-fuse python3-pylibacl python3-pyxattr python3-update-manager ubuntu-release-upgrader-core
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  git
0 upgraded, 0 newly installed, 1 to remove and 22 not upgraded.
After this operation, 19.6 MB disk space will be freed.

Usually it's not suggested to use apt remove because it will not remove the packages that were installed as dependencies. apt autoremove is suggested to remove the packages that are no longer needed.

Autoremove

Autoremove will remove the package and all packages that were installed as dependencies but are no longer needed.

sudo apt autoremove git

This command will remove the git package and all packages that were installed as dependencies but are no longer needed.

anduin@u-real:~$ sudo apt autoremove git
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages will be REMOVED:
  bup bup-doc git git-man liberror-perl python3-distupgrade python3-fuse python3-pylibacl python3-pyxattr python3-update-manager ubuntu-release-upgrader-core
0 upgraded, 0 newly installed, 11 to remove and 22 not upgraded.
After this operation, 23.4 MB disk space will be freed.
Do you want to continue? [Y/n]

apt autoremove can also be used without a package name. It will remove all packages that are no longer needed.

Inside apt, there is a reference-counting mechanism to track the number of packages that depend on a package. When a package is removed, the reference count is decreased. When the reference count reaches zero, the package is no longer needed and can be autoremoved.

anduin@host:~$ sudo apt autoremove
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages will be REMOVED:
  python3-distupgrade python3-update-manager ubuntu-release-upgrader-core
0 upgraded, 0 newly installed, 3 to remove and 22 not upgraded.
After this operation, 1,270 kB disk space will be freed.
Do you want to continue? [Y/n] 
(Reading database ... 338310 files and directories currently installed.)
Removing ubuntu-release-upgrader-core (1:22.04.19) ...
Removing python3-distupgrade (1:22.04.19) ...
Removing python3-update-manager (1:22.04.20) ...
Processing triggers for man-db (2.10.2-1) ...

Remove\Autoremove with --purge

--purge is an argument that can be used with apt remove and apt autoremove. It will remove the package and all configuration files.

sudo apt     remove --purge git
sudo apt autoremove --purge git

If you don't want to keep the configuration files, use --purge.

apt purge is actually the same as apt remove --purge. Here purge is just a shorthand for remove --purge.

Unlike autoremoving can run without a package name, purging must have a package name.

Update

apt update is used to update the package list. It will download the latest package list from the repositories.

sudo apt update

It is required to run apt update before running other commands because only apt update will download the latest package list from the repositories.

apt update will read the sources at /etc/apt/sources.list and /etc/apt/sources.list.d/ and download the latest package list from the repositories.

anduin@host:~$ cat /etc/apt/sources.list
deb http://mirror.aiursoft.cn/ubuntu/ jammy main restricted universe multiverse
deb http://mirror.aiursoft.cn/ubuntu/ jammy-updates main restricted universe multiverse
deb http://mirror.aiursoft.cn/ubuntu/ jammy-backports main restricted universe multiverse
deb http://mirror.aiursoft.cn/ubuntu/ jammy-security main restricted universe multiverse

anduin@host:$ cat /etc/apt/sources.list.d/google-earth-pro.list
deb [arch=amd64] http://dl.google.com/linux/earth/deb/ stable main

You can add thrird-party repositories to /etc/apt/sources.list.d/ and run apt update to download the latest package list from the third-party repositories.

apt update takes no arguments.

Upgrade

apt upgrade is used to upgrade the installed packages to the latest version.

sudo apt upgrade

Search

apt search is used to search for packages.

sudo apt search dotnet

This will output a list of packages that match the search term.

List

apt list is used to list all packages. apt list is similar to apt search, but it will list all packages matches the search term. Like dotnet* will list all packages that start with dotnet.

anduin@host:/etc/apt/sources.list.d$ sudo apt list dotnet*
Listing... Done
dotnet-apphost-pack-6.0/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet-apphost-pack-7.0/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet-apphost-pack-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-host-7.0/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet-host-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-host/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet-hostfxr-6.0/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet-hostfxr-7.0/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet-hostfxr-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-runtime-6.0/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet-runtime-7.0/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet-runtime-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-runtime-dbg-8.0/jammy-updates,jammy-security 8.0.7-0ubuntu1~22.04.1 amd64
dotnet-sdk-6.0-source-built-artifacts/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet-sdk-6.0/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet-sdk-7.0-source-built-artifacts/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet-sdk-7.0/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet-sdk-8.0-source-built-artifacts/jammy-updates,jammy-security 8.0.107-0ubuntu1~22.04.1 amd64
dotnet-sdk-8.0/jammy-updates,jammy-security,now 8.0.107-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-sdk-dbg-8.0/jammy-updates,jammy-security 8.0.107-0ubuntu1~22.04.1 amd64
dotnet-targeting-pack-6.0/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet-targeting-pack-7.0/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet-targeting-pack-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-templates-6.0/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet-templates-7.0/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet-templates-8.0/jammy-updates,jammy-security,now 8.0.107-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet6/jammy-updates,jammy-security 6.0.132-0ubuntu1~22.04.1 amd64
dotnet7/jammy-updates,jammy-security 7.0.119-0ubuntu1~22.04.1 amd64
dotnet8/jammy-updates,jammy-security,now 8.0.107-8.0.7-0ubuntu1~22.04.1 amd64 [installed]

apt list can also be used without a package name. It will list all packages.

More commonly, apt list is used to list all packages installed on the system.

sudo apt list --installed

For example, if I want to list all dotnet* on my system, I can use apt list --installed dotnet*.

anduin@u-real:/etc/apt/sources.list.d$ sudo apt list dotnet* --installed
Listing... Done
dotnet-apphost-pack-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-host-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-hostfxr-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-runtime-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-sdk-8.0/jammy-updates,jammy-security,now 8.0.107-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-targeting-pack-8.0/jammy-updates,jammy-security,now 8.0.7-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet-templates-8.0/jammy-updates,jammy-security,now 8.0.107-0ubuntu1~22.04.1 amd64 [installed,automatic]
dotnet8/jammy-updates,jammy-security,now 8.0.107-8.0.7-0ubuntu1~22.04.1 amd64 [installed]

Show

In some cases, I need to know the details of a package. apt show is used to show the details of a package.

anduin@host:/etc/apt/sources.list.d$ sudo apt show git
Package: git
Version: 1:2.34.1-1ubuntu1.11
Priority: optional
Section: vcs
Origin: Ubuntu
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: Jonathan Nieder <jrnieder@gmail.com>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 18.9 MB
Provides: git-completion, git-core
Depends: libc6 (>= 2.34), libcurl3-gnutls (>= 7.56.1), libexpat1 (>= 2.0.1), libpcre2-8-0 (>= 10.34), zlib1g (>= 1:1.2.0), perl, liberror-perl, git-man (>> 1:2.34.1), git-man (<< 1:2.34.1-.)
Recommends: ca-certificates, patch, less, ssh-client
Suggests: gettext-base, git-daemon-run | git-daemon-sysvinit, git-doc, git-email, git-gui, gitk, gitweb, git-cvs, git-mediawiki, git-svn
Breaks: bash-completion (<< 1:1.90-1), cogito (<= 0.18.2+), dgit (<< 5.1~), git-buildpackage (<< 0.6.5), git-el (<< 1:2.32.0~rc2-1~), gitosis (<< 0.2+20090917-7), gitpkg (<< 0.15), guilt (<< 0.33), openssh-client (<< 1:6.8), stgit (<< 0.15), stgit-contrib (<< 0.15)
Homepage: https://git-scm.com/
Task: cloud-image, ubuntu-wsl, server, ubuntu-server-raspi, kubuntu-desktop, lubuntu-desktop, ubuntustudio-desktop-core, ubuntustudio-desktop
Download-Size: 3,165 kB
APT-Manual-Installed: yes
APT-Sources: http://mirror.aiursoft.cn/ubuntu jammy-updates/main amd64 Packages
Description: fast, scalable, distributed revision control system
 Git is popular version control system designed to handle very large
 projects with speed and efficiency; it is used for many high profile
 open source projects, most notably the Linux kernel.
 .
 Git falls in the category of distributed source code management tools.
 Every Git working directory is a full-fledged repository with full
 revision tracking capabilities, not dependent on network access or a
 central server.
 .
 This package provides the git main components with minimal dependencies.
 Additional functionality, e.g. a graphical user interface and revision
 tree visualizer, tools for interoperating with other VCS's, or a web
 interface, is provided as separate git* packages.

N: There is 1 additional record. Please use the '-a' switch to see it

As you can see here, apt show also shows the dependencies, the size of the package, the origin, the maintainer, the homepage, and the description of the package.

If you run apt install git here, it will also install the dependencies, including libc6, libcurl3-gnutls, libexpat1, libpcre2-8-0, zlib1g, perl, liberror-perl, and git-man.

And you can not remove a dependency package without removing the package that depends on it. For example, you can not remove libc6 without removing git.

anduin@host:/etc/apt/sources.list.d$ sudo apt autoremove git-man
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages will be REMOVED:
  bup bup-doc ****git**** git-man liberror-perl python3-fuse python3-pylibacl python3-pyxattr
0 upgraded, 0 newly installed, 8 to remove and 3 not upgraded.
After this operation, 22.2 MB disk space will be freed.
Do you want to continue? [Y/n]

In this case, git-man is a dependency of git. If you remove git-man, git will also be removed.

Clean

apt clean is used to clean the cache. It will remove all downloaded packages from the cache.

sudo apt clean

Advanced usages

Right here covers advanced usages of apt.

Pinning

Pinning is an advanced usage that allows you to control which versions of packages are installed on your system. You can specify preferences for package versions by creating or editing files in /etc/apt/preferences.d/.

To pin a specific package version, create a file in /etc/apt/preferences.d/ with the following format:

Package: package-name
Pin: version x.y.z
Pin-Priority: 1001

Example for pinning git to version 2.34.1:

Package: git
Pin: version 2.34.1
Pin-Priority: 1001

Save this configuration in a file, such as /etc/apt/preferences.d/git.

You can also use this trick to avoid installing a specific package or version. For example, to avoid installing snapd, you can create a file in /etc/apt/preferences.d/ with the following content:

cat << EOF > /etc/apt/preferences.d/no-snap.pref
Package: snapd
Pin: release a=*
Pin-Priority: -10
EOF

Check the files inside a package

apt-file is a tool that can be used to check the files inside a package.

sudo apt install apt-file

After installing apt-file, you need to update the package list.

sudo apt-file update

Then you can use apt-file to check the files inside a package.

anduin@host:~$ apt-file list ubuntu-wallpapers
ubuntu-wallpapers: /usr/share/backgrounds/ubuntu-default-greyscale-wallpaper.png
ubuntu-wallpapers: /usr/share/backgrounds/warty-final-ubuntu.png
ubuntu-wallpapers: /usr/share/doc/ubuntu-wallpapers/changelog.Debian.gz
ubuntu-wallpapers: /usr/share/doc/ubuntu-wallpapers/copyright
ubuntu-wallpapers: /usr/share/gnome-background-properties/ubuntu-wallpapers.xml

As you can see above, ubuntu-wallpapers contains the files for /usr/share/backgrounds and /usr/share/gnome-background-properties.

Query which packages depend on a package

apt-cache is a tool that can be used to query which packages depend on a package.

apt-cache rdepends package-name

For example, to query which packages depend on ubuntu-wallpapers, you can use the following command:

anduin@u-real:~$ apt-cache rdepends ubuntu-wallpapers
ubuntu-wallpapers
Reverse Depends:
  ubuntu-wallpapers-xenial
  ubuntu-desktop-minimal
  ubuntu-desktop
  gnome-shell
  ubuntu-wallpapers-xenial
  ubuntu-wallpapers-focal
  ubuntu-wallpapers-focal
  ubuntu-wallpapers-eoan
  ubuntu-wallpapers-eoan
  ubuntu-wallpapers-cosmic
  ubuntu-wallpapers-disco
  ubuntu-wallpapers-disco
  ubuntu-wallpapers-cosmic
  gnome-shell
  ubuntu-artwork
  ubuntu-desktop-minimal
  ubuntu-desktop

Adding new repositories

Before starting, to have the add-apt-repository command, you need to install software-properties-common.

sudo apt install software-properties-common

For example, if you want to install nextcloud, you may want to:

sudo add-apt-repository -y ppa:nextcloud-devs/client

And then you can install nextcloud-client with:

sudo apt install nextcloud-client

Here are other examples:

sudo add-apt-repository -y ppa:mozillateam/ppa # Firefox
sudo add-apt-repository -y ppa:apandada1/plots # Plots
sudo add-apt-repository -y multiverse -n
sudo add-apt-repository -y universe -n
sudo add-apt-repository -y restricted -n

To query added repositories, you can use:

cd /etc/apt/sources.list.d/
ls

Setting up your own apt mirror

Reference here