How to Use the Apt-Get Command in Linux?

The Advanced Packaging Tool (APT) is a powerful command-line tool used in Debian-based systems like Ubuntu, Linux Mint, and others. The apt-get command is one of the most common ways to interact with APT. It's used to handle packages, allowing you to install, upgrade, and remove software on your Linux system.

In this guide, we'll walk you through the essential apt-get commands with practical examples and their outputs.

Updating Package Lists

The first command you should know is apt-get update. This command retrieves information about the newest versions of packages and their dependencies. It doesn't install or upgrade any packages, but updates the local package database for upgrades and new installations.

sudo apt-get update

Hit:1 http://archive.ubuntu.com/ubuntu bionic InRelease
Get:2 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:3 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Reading package lists... Done

Upgrading Packages

Once you've updated your package lists, you can upgrade your installed packages with apt-get upgrade. This command installs the newest versions of all packages currently installed on the system.

sudo apt-get upgrade

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
  libssl1.1 openssl
2 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,374 kB of archives.
After this operation, 1,024 B of additional disk space will be used.
Do you want to continue? [Y/n]

Installing Packages

To install a new package, use the apt-get install command followed by the package name. APT automatically resolves and installs any required dependencies.

sudo apt-get install firefox

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  firefox-locale-en
Suggested packages:
  fonts-lyx
The following NEW packages will be installed:
  firefox firefox-locale-en
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 49.4 MB of archives.
After this operation, 182 MB of additional disk space will be used.
Do you want to continue? [Y/n]

Removing and Purging Packages

There are two ways to remove packages

Remove (Keep Configuration Files)

sudo apt-get remove firefox

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be removed:
  firefox firefox-locale-en
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 182 MB disk space will be freed.
Do you want to continue? [Y/n]

Purge (Remove Everything Including Configuration)

sudo apt-get purge firefox

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be removed:
  firefox* firefox-locale-en*
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 182 MB disk space will be freed.
Do you want to continue? [Y/n]

System Cleanup Commands

Autoremove Unused Dependencies

When packages are removed, their dependencies might become orphaned. The autoremove command removes these unnecessary packages.

sudo apt-get autoremove

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be REMOVED:
  libfreetype6 libjpeg-turbo8 libjpeg8 libjbig0 libtiff5
0 upgraded, 0 newly installed, 5 to remove and 0 not upgraded.
After this operation, 1,525 kB disk space will be freed.
Do you want to continue? [Y/n]

Clean Package Cache

The clean command removes downloaded .deb files from /var/cache/apt/archives/ to free up disk space.

sudo apt-get clean

Advanced Package Operations

Install Specific Package Version

sudo apt-get install apache2=2.4.29-1ubuntu4.14

Download Package Without Installing

apt-get download apache2

Get:1 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 apache2 amd64 2.4.29-1ubuntu4.14 [95.1 kB]
Fetched 95.1 kB in 1s (67.8 kB/s)

Package Information Commands

Check Installed Packages

dpkg -l | grep apache2

ii  apache2       2.4.29-1ubuntu4.14  amd64  Apache HTTP Server
ii  apache2-bin   2.4.29-1ubuntu4.14  amd64  Apache HTTP Server (modules and other binary files)
ii  apache2-data  2.4.29-1ubuntu4.14  all    Apache HTTP Server (common files)

List All Installed Packages

dpkg --get-selections

adduser                                         install
apache2                                         install
apache2-bin                                     install
apache2-data                                    install
apt                                             install
...

Common Usage Patterns

Conclusion

The apt-get command is an essential tool for managing packages on Debian-based Linux systems. It provides comprehensive package management capabilities from installation and updates to cleanup and maintenance. Always use sudo for system-level operations and be cautious when removing packages to avoid breaking system dependencies.