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Debian DEB Packages

Introduction​

Debian packages (commonly known as DEB packages) are the standard software packaging format used by Debian and Debian-based Linux distributions like Ubuntu, Linux Mint, and many others. These packages contain application files, configuration data, and installation instructions bundled together in a single .deb file.

Understanding DEB packages is fundamental for anyone learning Linux system administration or development on Debian-based systems. In this guide, we'll explore what DEB packages are, how they work, and how to manage them effectively.

What is a DEB Package?​

A DEB package is essentially an archive file with the .deb extension. It contains software in a structured format that the Debian package management system can understand and process.

DEB packages are built according to specific standards that ensure consistency and compatibility across different Debian-based systems.

Anatomy of a DEB Package​

A DEB package consists of three main components:

  1. Debian binary package control file (debian-binary) - Contains the version of the package format
  2. Control archive (control.tar.gz or control.tar.xz) - Contains metadata about the package
  3. Data archive (data.tar.gz, data.tar.xz, etc.) - Contains the actual files to be installed

Control Information​

The control archive contains important metadata about the package, including:

  • Package name and version
  • Dependencies and conflicts with other packages
  • Maintainer information
  • Architecture compatibility
  • Package description
  • Pre and post-installation scripts

Let's look at an example of a control file:

Package: hello
Version: 2.10-2
Architecture: amd64
Maintainer: John Doe <[email protected]>
Installed-Size: 120
Depends: libc6 (>= 2.14)
Section: utils
Priority: optional
Description: The classic greeting program
 The GNU hello program produces a familiar, friendly greeting.
 It allows non-programmers to use a classic computer science tool
 which would otherwise be unavailable to them.

Data Files​

The data archive contains the actual files that will be installed on the system, organized in the same directory structure where they'll be placed. This includes:

  • Executable binaries
  • Libraries and shared files
  • Configuration files
  • Documentation and man pages
  • Desktop icons and application entries

Working with DEB Packages​

Installing DEB Packages​

You can install DEB packages using various tools. The most basic tool is dpkg, the Debian Package Manager:

bash
sudo dpkg -i package-name.deb

However, dpkg doesn't resolve dependencies automatically. For that, you'll want to use higher-level tools like apt:

bash
sudo apt install ./package-name.deb

Example of installing the Firefox browser:

bash
# Using dpkg
sudo dpkg -i firefox_98.0+build2-0ubuntu0.20.04.1_amd64.deb
# If there are dependency problems
sudo apt -f install

# Using apt (automatically handles dependencies)
sudo apt install ./firefox_98.0+build2-0ubuntu0.20.04.1_amd64.deb

Listing Installed Packages​

To see what packages are installed on your system:

bash
# List all installed packages
dpkg -l

# Find specific packages
dpkg -l | grep firefox

Example output:

ii  firefox                               98.0+build2-0ubuntu0.20.04.1   amd64   Safe and easy web browser from Mozilla

The first column shows the package status:

  • ii means the package is installed correctly
  • rc means the package was removed but configuration files remain
  • un means the package is unknown/not installed

Querying Package Information​

To get detailed information about a package:

bash
# For an installed package
dpkg -s firefox

# For a .deb file
dpkg -I firefox_98.0+build2-0ubuntu0.20.04.1_amd64.deb

Example output:

Package: firefox
Status: install ok installed
Priority: optional
Section: web
Installed-Size: 221807
Maintainer: Ubuntu Mozilla Team <[email protected]>
Architecture: amd64
Version: 98.0+build2-0ubuntu0.20.04.1
Depends: lsb-release, libatk1.0-0 (>= 1.12.4), [...]
Description: Safe and easy web browser from Mozilla
 Firefox delivers safe, easy web browsing. A familiar user interface,
 enhanced security features including protection from online identity theft,
 and integrated search let you get the most out of the web.

Listing Package Contents​

To see what files a package contains:

bash
# For an installed package
dpkg -L firefox

# For a .deb file
dpkg -c firefox_98.0+build2-0ubuntu0.20.04.1_amd64.deb

Example output:

/usr/lib/firefox/
/usr/lib/firefox/firefox
/usr/lib/firefox/firefox-bin
/usr/lib/firefox/browser/chrome.manifest
/usr/lib/firefox/browser/omni.ja
[...]

Removing Packages​

To remove an installed package:

bash
# Remove the package but keep configuration files
sudo dpkg -r firefox
# or
sudo apt remove firefox

# Remove the package and its configuration files
sudo dpkg --purge firefox
# or
sudo apt purge firefox

Creating a Simple DEB Package​

Let's walk through creating a simple DEB package for a "hello world" program:

1. Create the Program​

First, create a simple C program:

bash
mkdir -p hello-world/src
cd hello-world/src

Create a file named hello.c:

c
#include <stdio.h>

int main() {
    printf("Hello, Debian Package World!
");
    return 0;
}

Compile it:

bash
gcc -o hello hello.c

2. Prepare Package Directory Structure​

bash
mkdir -p ../debian-package/DEBIAN
mkdir -p ../debian-package/usr/local/bin

3. Create Control File​

Create a file named control in the DEBIAN directory:

bash
cat > ../debian-package/DEBIAN/control << EOF
Package: hello-world
Version: 1.0-1
Section: utils
Priority: optional
Architecture: amd64
Depends: libc6 (>= 2.14)
Maintainer: Your Name <[email protected]>
Description: Hello World Package
 This is a simple hello world package to demonstrate
 how to create Debian packages.
EOF

4. Copy Files to Package Structure​

bash
cp hello ../debian-package/usr/local/bin/

5. Build the Package​

bash
cd ..
dpkg-deb --build debian-package

This will create debian-package.deb, which you can install with:

bash
sudo dpkg -i debian-package.deb

After installation, you can run:

bash
hello-world

Output:

Hello, Debian Package World!

Using Higher-Level Tools for Package Creation​

For more complex packages, you might want to use higher-level tools like dh-make and debhelper:

bash
# Install the necessary tools
sudo apt install dh-make devscripts build-essential

# Set up environment variables
export DEBEMAIL="[email protected]"
export DEBFULLNAME="Your Name"

# Create a new package using a template
cd hello-world
dh_make --native --single --yes

This creates a debian/ directory with various template files that you can customize. After editing these files, you can build the package with:

bash
debuild -us -uc

Package Management Best Practices​

  1. Always use package management tools instead of manual installation when possible
  2. Keep your system updated:
    bash
    sudo apt update
    sudo apt upgrade
  3. Check package authenticity before installation
  4. Back up configuration files before significant changes
  5. Use virtual machines or containers for testing packages
  6. Review package contents before installation using dpkg -c

Advanced Package Management​

APT vs DPKG​

While dpkg is the low-level package manager, APT (Advanced Package Tool) provides a higher-level interface that automatically handles dependencies and package sources:

Package Repositories​

APT uses repositories - collections of packages stored on remote servers. These are configured in the /etc/apt/sources.list file and in the /etc/apt/sources.list.d/ directory.

bash
# View your current repositories
cat /etc/apt/sources.list

Example:

deb http://archive.ubuntu.com/ubuntu/ focal main restricted
deb http://archive.ubuntu.com/ubuntu/ focal-updates main restricted

Pinning Packages​

Sometimes you might want to control which version of a package is installed. This can be done with "pinning":

Create a file in /etc/apt/preferences.d/:

Package: firefox
Pin: version 90.*
Pin-Priority: 1001

This will prefer Firefox version 90.x over newer versions.

Summary​

Debian DEB packages provide a powerful and consistent way to distribute and manage software on Debian-based systems. In this guide, we've covered:

  • What DEB packages are and their internal structure
  • How to install, query, and remove packages
  • Creating a simple custom DEB package
  • Advanced package management concepts

Understanding DEB packages gives you greater control over your Debian-based system and is a foundational skill for Linux system administration.

Further Learning​

Exercises​

  1. Find and install a DEB package from the official Debian repositories
  2. Examine the control information of five different packages on your system
  3. Create a custom DEB package that installs a simple shell script
  4. Try building a package from source code using dh-make

Additional Resources​


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