Lesson 6.1: APT Package Manager

APT (Advanced Package Tool) is Ubuntu's traditional package management system. It's powerful, reliable, and deeply integrated with the operating system, making it perfect for system software and libraries.

Why APT? APT handles complex dependency resolution automatically, provides system-wide updates, and maintains package integrity through cryptographic signatures.

Understanding APT

APT is a front-end to the dpkg package manager:

dpkg: Low-level package manager (handles individual .deb files)
APT: High-level package manager (handles repositories and dependencies)
apt-cache: Query package information
apt-get: Traditional APT interface (still widely used)

Basic APT Commands

Let's start with essential APT commands you'll use daily:

Update Package Lists

Always update before installing new software:

$ sudo apt update Get:1 http://archive.ubuntu.com/ubuntu jammy InRelease [270 kB] Get:2 http://archive.ubuntu.com/ubuntu jammy-updates InRelease [114 kB] Fetched 384 kB in 1s (452 kB/s) Reading package lists... Done

Upgrade Packages

Upgrade all installed packages to latest versions:

$ sudo apt upgrade Reading package lists... Done Building dependency tree... Done Calculating upgrade... Done The following packages will be upgraded: firefox (119.0.1-1build1 -> 120.0-1build1) libssl1.1 (3.0.2-0ubuntu1.7 -> 3.0.2-0ubuntu1.8) Do you want to continue? [Y/n] Y

Install Packages

Install new software with a single command:

$ sudo apt install git Reading package lists... Done Building dependency tree... Done The following NEW packages will be installed: git git-man liberror-perl-perl libgit2-34 libx11-6 Suggested packages: git-daemon-sysvinit git-doc git-el git-email git-gui gitk gitweb Do you want to continue? [Y/n] Y

Remove Packages

Uninstall software you no longer need:

$ sudo apt remove git Reading package lists... Done Building dependency tree... Done The following packages will be REMOVED: git git-man libgit2-34 Do you want to continue? [Y/n] Y

Searching for Packages

Find software using APT's search capabilities:

Basic Search

$ apt search web browser firefox/jammy-updates,jammy-security 120.0-1build1 amd64 Safe and easy web browser from Mozilla chromium-browser/jammy-updates,jammy-security 1:108.0.5359.124-0ubuntu0.1 amd64 Chromium web browser, open-source version of Chrome lynx/jammy 2.8.9rel.1-2build1 amd64 Classic text-based web browser

Detailed Search

Get more information about packages:

$ apt show firefox Package: firefox Version: 120.0-1build1 Priority: optional Section: web Maintainer: Ubuntu Mozilla Team Description-en: Safe and easy web browser from Mozilla Firefox delivers safe, easy web browsing.

Package Information

Get detailed information about installed packages:

List Installed Packages

$ apt list --installed Listing... Done adduser/jammy,jammy 3.118ubuntu5 all apt/jammy,jammy 2.4.8 amd64 base-files/jammy,jammy 12ubuntu4.5 amd64 bash/jammy,jammy 5.1-6ubuntu1 amd64

Package Details

$ apt policy firefox firefox: Installed: 120.0-1build1 Candidate: 120.0-1build1 Version table: ***120.0-1build1 500 500 http://archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages 119.0.1-1build1 500 500 http://archive.ubuntu.com/ubuntu jammy/main amd64 Packages

Advanced APT Operations

Master these advanced APT commands for better package management:

Full System Upgrade

Upgrade packages and install new dependencies:

$ sudo apt full-upgrade Reading package lists... Done Calculating upgrade... Done The following packages will be upgraded: linux-headers-generic linux-image-generic The following NEW packages will be installed: linux-headers-5.15.0-78-generic linux-image-5.15.0-78-generic

Remove Configuration Files

Completely remove packages including configuration:

$ sudo apt purge git Reading package lists... Done The following packages will be REMOVED: git* git-man* libgit2-34* Purging configuration files for git (120.0-1build1) ...

Clean Up

Remove cached package files to free disk space:

$ sudo apt autoremove Reading package lists... Done The following packages will be REMOVED: liberror-perl-perl libx11-6 $ sudo apt autoclean Reading package lists... Done Del /var/cache/apt/archives/*.deb files

Managing Repositories

APT uses repositories to find packages. Ubuntu includes several by default:

Default Repositories

Main: Officially supported open-source software
Universe: Community-maintained software
Restricted: Proprietary drivers and firmware
Multiverse: Software restricted by copyright/patents

Adding Repositories

Add third-party repositories for additional software:

# Add PPA (Personal Package Archive) $ sudo add-apt-repository ppa:deadsnakes/ppa # Add repository manually $ sudo add-apt-repository "deb [arch=amd64] https://download.virtualbox.org/virtualbox/debian jammy contrib" # After adding repositories, always update $ sudo apt update

Repository Management

# List repositories $ apt policy # Remove repository $ sudo add-apt-repository --remove ppa:deadsnakes/ppa # View repository sources $ cat /etc/apt/sources.list $ ls /etc/apt/sources.list.d/

Package Pinning

Control package versions with pinning:

Hold Packages

Prevent packages from being upgraded:

# Hold a package $ sudo apt-mark hold firefox # Unhold a package $ sudo apt-mark unhold firefox # Show held packages $ sudo apt-mark showhold firefox

APT Configuration

Customize APT behavior with configuration files:

Main Configuration

Primary APT configuration is in /etc/apt/apt.conf:

# Example configuration APT::Get::Assume-Yes "true"; APT::Get::Show-Versions "true"; Acquire::Languages "none";

Repository Sources

Repository definitions are in /etc/apt/sources.list and /etc/apt/sources.list.d/:

# /etc/apt/sources.list example deb http://archive.ubuntu.com/ubuntu/ jammy main restricted deb http://archive.ubuntu.com/ubuntu/ jammy-updates main restricted deb http://archive.ubuntu.com/ubuntu/ jammy universe deb http://archive.ubuntu.com/ubuntu/ jammy-updates universe

APT vs apt-get

Modern APT vs traditional apt-get:

Recommended APT Commands

apt install instead of apt-get install
apt remove instead of apt-get remove
apt upgrade instead of apt-get upgrade
apt full-upgrade instead of apt-get dist-upgrade

Why Use apt?

Better progress reporting
Colored output
More informative package information
Integrated search functionality

Common APT Tasks

Real-world APT usage scenarios:

Installing Development Tools

# Install common development packages $ sudo apt install build-essential git python3 nodejs npm # Install LAMP stack $ sudo apt install apache2 mysql-server php libapache2-mod-php

System Maintenance

# Regular maintenance routine $ sudo apt update $ sudo apt upgrade $ sudo apt autoremove $ sudo apt autoclean

Troubleshooting

# Fix broken packages $ sudo apt --fix-broken install # Reconfigure packages $ sudo dpkg-reconfigure package-name # Check package integrity $ sudo apt check

Security Considerations

Keep your system secure with APT:

Verify Package Signatures

APT automatically verifies package signatures:

# Check repository keys $ apt-key list # Add repository key $ sudo apt-key add keyfile.asc

Security Updates

# Install security updates only $ sudo apt install unattended-upgrades $ sudo dpkg-reconfigure -plow unattended-upgrades # Check for security updates $ sudo apt list --upgradable | grep -i security

Practice Exercises

Exercise 1: Basic Package Management

Update package lists
Search for a text editor
Install the text editor
Check installed version
Remove the text editor

Click for solution

$ sudo apt update $ apt search text editor $ sudo apt install nano $ apt policy nano $ sudo apt remove nano

Exercise 2: System Maintenance

Perform full system upgrade
Remove unnecessary packages
Clean package cache
Add a PPA repository
Install software from the PPA

Click for solution

$ sudo apt update $ sudo apt full-upgrade $ sudo apt autoremove $ sudo apt autoclean $ sudo add-apt-repository ppa:libreoffice/ppa $ sudo apt update $ sudo apt install libreoffice

What's Next?

Now that you understand APT, let's explore Flatpak, which provides universal application deployment across different Linux distributions!

Continue to Flatpak Applications

Key Takeaways

APT is Ubuntu's traditional package management system
Always run apt update before installing software
Use apt upgrade for regular system updates
APT handles dependencies automatically
Repositories provide trusted, signed packages
Modern apt is preferred over apt-get