Linux Package Management: APT and DNF

What is a Package Manager?

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A package manager handles installing, updating, and removing software on your system. Instead of downloading binaries manually, you tell the package manager what you want and it:

1. Finds the software in a repository (a trusted server hosting packages)
2. Resolves dependencies (other packages the software needs)
3. Downloads and installs everything in the right place
4. Tracks what’s installed so it can update or remove it later

Every major Linux distribution ships with a package manager. The two most common are:

Repositories

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Repositories are remote servers that host packages. Your system is configured to trust specific repos and pull software from them.

Viewing configured repositories

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Adding a repository

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apt:

# Add a PPA (Ubuntu)
sudo add-apt-repository ppa:example/repo

# Add a third-party repo manually
echo "deb https://packages.example.com/ubuntu jammy main" | sudo tee /etc/apt/sources.list.d/example.list
sudo apt update

dnf:

# Add a repo from a URL
sudo dnf config-manager --add-repo https://packages.example.com/fedora/example.repo

# Or install a repo package
sudo dnf install https://packages.example.com/example-release.rpm

Core Operations

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Update package lists / metadata

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Before installing software, sync your local package database with the repos:

apt requires this as a separate step. dnf refreshes metadata automatically when needed but you can check manually.

Install a package

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Remove a package

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Upgrade installed packages

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Searching for Packages

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Working with Package Files

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Sometimes you need to install a package file directly (downloaded from a website, for example):

Both will resolve dependencies from your configured repos automatically.

Package Information and History

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What files does a package install?

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Which package owns a file?

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Transaction history

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dnf keeps a log of everything it’s done:

# View history
dnf history

# Undo the last transaction
sudo dnf history undo last

apt logs to /var/log/apt/history.log:

cat /var/log/apt/history.log

Holding / Locking Package Versions

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Prevent a package from being upgraded:

apt:

# Hold a package
sudo apt-mark hold nginx

# Release the hold
sudo apt-mark unhold nginx

# View held packages
apt-mark showhold

dnf:

# Install the versionlock plugin if needed
sudo dnf install dnf-plugins-core

# Lock a package
sudo dnf versionlock add nginx

# Remove the lock
sudo dnf versionlock delete nginx

# List locks
dnf versionlock list

Cleaning Up

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Understanding Dependencies

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When you install a package, the package manager pulls in everything it needs:

# See what a package depends on
apt depends nginx
dnf deplist nginx

# See what depends on a package (reverse dependencies)
apt rdepends nginx
dnf repoquery --whatrequires nginx

Dependency conflicts are rare with standard repos but can happen when mixing third-party repositories. If you hit a conflict:

1. Read the error — it usually names the conflicting packages
2. Check if you have third-party repos that overlap with official ones
3. Prefer the official repo version unless you have a specific reason not to

Key Differences Between apt and dnf

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Other Package Managers

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You’ll encounter these on other distributions:

The concepts are the same across all of them — repos, dependencies, install, remove, update. Only the commands differ.

Best Practices

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• Run apt update before installing anything on Debian/Ubuntu — stale metadata causes “package not found” errors
• Use autoremove periodically to clean up orphaned dependencies
• Prefer official repos over third-party ones — they’re tested against your distribution
• Don’t mix packages from different distribution versions — a package built for Ubuntu 24.04 may break on 22.04
• Use version locks when you need stability on a specific package version (databases, runtimes)
• Check dnf history or /var/log/apt/history.log when troubleshooting — knowing what changed helps isolate problems
• Keep your system updated — sudo apt upgrade or sudo dnf upgrade regularly patches security vulnerabilities