Debian APT Tutorial 2026: apt, apt-get, aptitude

Global Overview of APT

📖 Preamble

In the Debian ecosystem — Stable, Testing or Sid — APT (Advanced Package Tool) is the central software management tool. It relies on dpkg for individual package manipulation and provides a powerful interface to install, update and remove software, while automatically managing dependencies.

Guide Basis

This guide uses Debian 13 "trixie" as the Stable base, with Testing (forky) and Sid (unstable) as development branches. All commands and examples are verified for trixie.

Goal

Master APT progressively, from beginner to expert, with concrete practical use cases and verified commands.

👥 Target Audience

🌱

Beginner

Get up and running quickly
Sections: Starter Pack

🌿

Intermediate

Comprendre dépôts, priorités, updates
Sections : Concepts & Pratiques

🌳

Expert

Dépannage, migrations, commandes sensibles
Sections : Avancé & Critiques

📚 How to Read This Guide

Level	Content	Recommendation
🟢 Essential	Common commands, examples	Master first
🟠 Intermediate	Concepts, workflows	For deeper understanding
🔴 Expert	Critical cases, advanced operations	For experienced users only

❓ What is APT?

Element	Description
Role	Package manager for Debian and its derivatives
Engine	Based on dpkg
Strengths	Automatic dependency resolution, fine-grained repository management, stability, community
Audience	All Debian users, from beginners to administrators

📝 Basic Syntax

General Structure

APT Syntax

apt [OPTIONS] COMMANDE [ARGUMENTS]

apt-get [OPTIONS] COMMANDE [ARGUMENTS]

apt-cache [OPTIONS] COMMANDE [ARGUMENTS]

aptitude [OPTIONS] COMMANDE [ARGUMENTS]

Breakdown

Element	Role	Example
OPTIONS	Options applied to the command	-y, --simulate, -V
COMMAND	The main action to perform	install, remove, update, upgrade
ARGUMENTS	What the action applies to	Package name, version, .deb file

Annotated Example

Example

# Install htop without recommendations, auto yes mode

$sudo apt -y install --no-install-recommends htop

# -y = global option (auto yes)

# install = command

# --no-install-recommends = command option

# htop = argument

🧩 Distinction entre apt, apt-get, apt-cache et aptitude

Tool	Main Role	Interface	Audience
apt	Common user commands	Concise, colorful	Daily use
apt-get	Legacy package management	Bare, scripts	Automation
apt-cache	Cache querying	Command lines	Advanced searches
aptitude	Interactive text interface + CLI	Cursor/line mode	Complex conflict resolution

Recommendation: apt for interactive use, apt-get for scripts, apt-cache for precise queries, aptitude as a last resort.

🏗️ Internal Architecture: APT + dpkg

┌────────────┐     ┌──────────────────┐     ┌──────────────────┐
│    APT     │ ──▶ │       dpkg       │ ──▶ │  Linux System    │
└────────────┘     └──────────────────┘     └──────────────────┘
       │                    │                        │
       ▼                    ▼                        ▼
CLI Interface       Installation/Removal        File Management
Repository Mgmt     Package database            Maintainer scripts
Dependency            of installed packages
resolution

Component Roles

Component	Role	Importance
APT	User interface, repository management, dependency resolution	Daily interaction
dpkg	Actual installation, local database	System core
Pinning	Repository priority control	Stability / customization

📦 Repositories

Repository Role: The Foundation of Everything

Repositories are defined in /etc/apt/sources.list and /etc/apt/sources.list.d/.

┌─────────────────────┐
│  Debian 13 trixie   │  (main, contrib, non-free, non-free-firmware)
└─────────────────────┘
           │
┌─────────────────────┐
│  Debian Security    │  (security updates)
└─────────────────────┘
           │
┌─────────────────────┐
│  trixie-updates     │  (stable updates)
└─────────────────────┘
           │
┌─────────────────────┐
│  trixie-backports   │  (more recent versions, targeted use)
└─────────────────────┘

Repository Types

Type	Content	Notes
main	Official free packages	Supported by Debian
contrib	Free packages depending on non-free ones
non-free	Non-free packages	Proprietary drivers
non-free-firmware	Proprietary firmware (WiFi, GPU, microcode)	Required for much modern hardware — Debian 13+
security	Security patches	Essential for Stable
backports	Recent versions for Stable	Official, targeted use (not for the whole system)
experimental	Very fresh, unstable packages	For testing only

Repository Lifecycle

Ajouter manuellement
 │
 ▼
Modifier (éditer le fichier)
 │
 ▼
Activer / Désactiver (commenter)
 │
 ▼
Supprimer (effacer la ligne)

DEB822 Format — Recommended for Debian 13

New Recommended Format

Debian 13 trixie favors files in /etc/apt/sources.list.d/*.sources in DEB822 format to declare repositories. The sources.list format remains supported for compatibility.

DEB822 Example — /etc/apt/sources.list.d/debian.sources

Types: deb

URIs: http://deb.debian.org/debian

Suites: trixie trixie-updates

Components: main contrib non-free non-free-firmware

Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg

Types: deb

URIs: http://security.debian.org/debian-security

Suites: trixie-security

Components: main contrib non-free non-free-firmware

Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg

Best Practices by Use Case

Distribution	Recommended Repositories	Discouraged Repositories
Stable (trixie)	main, contrib, non-free, non-free-firmware, security, trixie-updates	experimental — backports: official but targeted use only
Testing (forky)	main, contrib, non-free, non-free-firmware	experimental (may desynchronize)
Sid	main, contrib, non-free, non-free-firmware	backports (useless on Sid)
Servers	main, non-free-firmware, security, trixie-updates	contrib, non-free if possible

⚖️ Repository Priorities (Pinning)

The APT priority system lets you control which repository takes precedence.

APT doit installer un paquet :
        │
        ▼
  1. Dépôt avec la priorité la plus élevée
        │
        ▼
  2. Version la plus récente (si priorités égales)
        │
        ▼
  3. Dependency resolution

Priority Meanings (Debian source)

P < 0: never installed
1-99: only if no other version is installed
100: default priority for already installed version
101-499: only if no higher priority source exists
500: standard priority of the target distribution
501-989: only if no newer version in the target
990-1000: unless installed version is more recent
>1000: always installed, even if forced downgrade

🔄 Stable vs Testing vs Sid — In 20 Seconds

🛡️

Stable — trixie

Debian 13, robust distribution

Type: Stable, frozen

Risks: Low

Use: Servers, production, desktop

Routine: apt upgrade

Transition: apt full-upgrade

🚀

Testing — forky

Future Debian, pre-release

Type: Frozen rolling

Risks: Moderate

Use: Desktop, testers

Command: apt full-upgrade

💥

Sid (Unstable)

Permanent rolling

Type: Rolling

Risks: High

Use: Developers, experts

Command: apt full-upgrade

APT Commands

🚀 Starter Pack — The 15 Essential Commands

sudo apt update

Refresh the package list

sudo apt upgrade

Standard update (Stable)

sudo apt full-upgrade

Full upgrade (Testing/Sid)

sudo apt install <pkg>

Install a package

sudo apt remove <pkg>

Remove (keeps config)

sudo apt purge <pkg>

Remove completely

apt search <pattern>

Search for a package (modern, colorful) — apt-cache search <pattern> for scripts

apt show <pkg>

Detailed information

apt list --installed

List installed packages

apt-file search <file>

Which package provides this file?

sudo apt autoremove

Remove unnecessary dependencies

sudo apt clean

Clean the cache

sudo apt autoclean

Clean obsolete packages

apt-mark showhold

Show locked packages

sudo apt --fix-broken install

Fix broken dependencies

📦 Repository Management

Inspect Repositories

Inspect

$apt-cache policy

$cat /etc/apt/sources.list

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

Add, Remove, Modify

Management

# Add a repository (manual)

$echo "deb http://deb.debian.org/debian trixie-backports main" | sudo tee /etc/apt/sources.list.d/backports.list

# Modify

$sudo apt edit-sources

# Remove

$sudo rm /etc/apt/sources.list.d/backports.list

🔍 Advanced apt-cache Commands

Command	Description
apt-cache policy [package]	Priorities and available versions
apt-cache showpkg <package>	Internal info (reverse dependencies)
apt-cache depends <package>	Lists dependencies
apt-cache rdepends <package>	Lists packages that depend on it
apt-cache stats	Cache statistics
apt-cache unmet ^⚠️	Unmet dependencies (deprecated on Debian 13 — prefer apt check)
apt-cache madison <package>	Available versions with origin

📥 Installation / Update / Removal

apt upgrade vs apt full-upgrade vs apt-get dist-upgrade

Criterion	upgrade	full-upgrade / dist-upgrade
Updates packages	✔️ Yes	✔️ Yes
Installs new packages	❌ No	✔️ Yes (if needed)
Removes packages	❌ No	✔️ Yes (if needed)
Recommended use	Stable	Testing, Sid, migration

Advanced Installation

Installation

# Install multiple packages

$sudo apt install git curl vim

# Specific version

$sudo apt install vim=2:9.0.1378-2

# From a specific distribution (e.g.: unstable)

$sudo apt install -t unstable apache2

$sudo apt install apache2/unstable

# Reinstall

$sudo apt install --reinstall bash

# Simulate

$sudo apt install --simulate htop

# Install a local .deb file (with dependency resolution)

$sudo apt install ./package.deb

Removal

$sudo apt remove htop

$sudo apt purge htop

$sudo apt remove --auto-remove htop

# Remove and install in one line (+/- syntax)

$sudo apt install package1 package2-

$sudo apt remove package1+ package2

Locks

$sudo apt-mark hold linux-image-amd64

$apt-mark showhold

$sudo apt-mark unhold linux-image-amd64

Cleanup

$sudo apt clean

$sudo apt autoclean

$sudo apt autoremove --purge

$sudo aptitude purge ~c

🛠️ Maintenance & Diagnostic

Broken Packages

Diagnostics

$sudo apt --fix-broken install

$sudo apt check

$sudo dpkg --configure -a

$dpkg -l | grep ^[a-z][a-z]

Blocking Processes

Processes

$sudo lsof | grep ' (deleted)'

$sudo needrestart

Dependencies and Consistency

Dependencies

$apt-cache depends <package>

$apt-cache rdepends <package>

$sudo debsums -c

⚡ Advanced Commands (Expert)

Working with Multiple Distributions

Multi-distrib

# Lock trixie as the default distribution (base of this guide)

echo 'APT::Default-Release "trixie";' | sudo tee /etc/apt/apt.conf.d/99default

# Install a package from Sid while keeping trixie as the base

$sudo apt install -t unstable package-name

Fine-grained Pinning

Pinning

# /etc/apt/preferences.d/pin-backports

Package: *

Pin: release a=trixie-backports

Pin-Priority: 100

Complementary Tools

Tool	Description	Example Command
apt-listbugs	Shows bugs before installation	apt-listbugs list apache2
apt-listchanges	Shows recent changes	apt-listchanges --apt
apt-rdepends	Recursive dependencies	apt-rdepends vlc
aptitude why	Why an auto package is installed	aptitude why python3
nala	Modern optional frontend for APT	apt install nala then nala --help

🔧 Tools Requiring Installation

Some advanced commands and tools mentioned in this guide are not installed by default on Debian. To use them, simply install the corresponding packages.

Tool	Role	Installation
apt-file	Find the package providing a file	sudo apt install apt-file
deborphan	List orphaned packages	sudo apt install deborphan
needrestart	Check which services need restarting after update	sudo apt install needrestart
apt-listbugs	Display bugs before installation	sudo apt install apt-listbugs
apt-listchanges	View recent package changes	sudo apt install apt-listchanges
aptitude	Interactive package management interface	sudo apt install aptitude
nala	Modern APT frontend (improved display)	sudo apt install nala

⚠️ Dangerous Commands — Red Zone

Warning

Some commands can break a system if used incorrectly.

Command	Danger
dpkg --force-depends -i package.deb	Ignores dependencies
apt-get -o Dpkg::Options::="--force-confnew" dist-upgrade	Overwrites modified config files
dpkg --purge --force-all <package>	Removes even with dependencies

Best Practices

Always simulate with --simulate
Back up configurations
Use apt-mark hold on critical packages

🏆 Top 12 Advanced APT Commands

sudo apt install -t <release> <pkg>

Install from a specific distribution

sudo apt-get --simulate dist-upgrade

Simulate an upgrade

apt-cache policy <pkg>

View versions and priorities

apt-file search <file>

Find the providing package

sudo apt build-dep <pkg>

Install build dependencies

apt-mark hold <pkg>

Lock a package

apt-cache rdepends <pkg>

View dependents

deborphan | xargs sudo apt purge -y

Purge orphaned packages

dpkg -S <file>

Find which package owns a file

aptitude search '~S'

Advanced search with patterns

sudo needrestart

Restart services after update

apt-cache madison <pkg>

All available versions

🎯 Advanced Practical Cases (GPS format)

Install a package from backports

Problem

Version too old

Command

sudo apt install -t trixie-backports firefox

Recover a system with broken dependencies

Command

sudo apt --fix-broken install

Minimal installation

Command

sudo apt install --no-install-recommends nginx

Clean downgrade

Command

sudo apt install <pkg>=<old-version>

Find the providing package

Command

apt-file search bin/lsmod

Check consistency

Commands

sudo apt check + sudo debsums -c

Simulate a risky removal

Command

apt remove --simulate libssl

Lock the kernel

Command

sudo apt-mark hold linux-image-amd64

See what depends on python3

Command

apt-cache rdepends --installed python3

A10

Build dependencies

Command

sudo apt build-dep vlc

A11

Clean orphaned packages

Command

sudo apt autoremove --purge

A12

Check bugs before installation

Command

apt-listbugs list apache2

🔗 Complete References

Official Debian Documentation

Source	Content
apt	Complete reference for the apt command
aptitude	Complete reference for aptitude
apt-get	Complete reference for apt-get
Aptitude vs. Apt-Get	Comparison and package authentication

Local Help Pages

Help

$apt install --help

$apt-get install --help

$apt search --help

$apt remove --help

$apt-get remove --help

$aptitude --help

📖 Recommended Reads — SafeITExperts

Source	Content
sudo vs su	Complete Guide to Linux Privilege Elevation
Desktop Environment Compatibilities	Linux Desktop Environment Compatibilities in 2025
Enable KDE Unstable Plasma on openSUSE	KDE Plasma on openSUSE Tumbleweed
Linux, Windows or macOS	8 Essential Criteria to Choose Your OS

🎯 Conclusion

APT is a powerful and mature tool that is one of Debian's greatest strengths. Mastering it requires understanding repositories, pinning, and the various commands available.

Key Points