Debian Packages
1. DEB Packaging Basics
Debian-based systems use the Debian Package Manager (DPKG) to handle software distribution, ensuring consistency, ease of installation, and maintenance.
Key Components of a DEB Package
1. Metadata:
Information about the package (e.g., name, version, architecture, dependencies).
2. Compiled Binaries:
Executables and libraries required for the software to function.
3. Configuration Files:
Default settings, typically stored in /etc.
4. Scripts:
Pre- and post-install/uninstall scripts for setup and cleanup tasks (preinst, postinst, prerm, postrm).
2. The Control File
The control file, located in DEBIAN/control, defines metadata and dependencies for the package. It is a crucial component of a DEB package.
Key Fields of a Control File
1. Package:
Specifies the name of the package.
2. Version:
Defines the version number of the package.
3. Architecture:
Indicates the target architecture (e.g., amd64, i386, all).
4. Description:
Provides a brief and detailed description of the package.
5. Maintainer:
Lists the package maintainer's name and email.
6. Dependencies:
Specifies required packages using Depends, Recommends, or Suggests.
3. Basic DPKG Commands
Managing DEB Packages
Install a Package
sudo dpkg -i package.deb
Remove a Package
sudo dpkg -r package-name
Query Installed Packages
dpkg -l | grep package-name
Verify Package Integrity
debsums -c package-name
Reconfigure a Package
sudo dpkg-reconfigure package-name
4. APT Package Manager
APT (Advanced Package Tool) is a higher-level interface for DPKG, providing dependency resolution and easier package management.
Install a Package
sudo apt install package-name
Remove a Package
sudo apt remove package-name
Update Package Index
sudo apt update
Upgrade All Packages
sudo apt upgrade
Search for a Package
apt search package-name
List Installed Packages
apt list --installed
5. Building DEB Packages
1. Create the Directory Structure
Organize files in the directory structure matching the target filesystem (e.g., /usr/bin, /etc, etc.).
2. Create the Control File
Define metadata in DEBIAN/control.
3. Build the Package
Use dpkg-deb to create the package:
dpkg-deb --build package-directory
4. Verify the Package
Inspect the contents of the package:
dpkg -c package.deb
6. Patching DEB Packages
Patching involves modifying a package to fix vulnerabilities or add customizations.
1. Extract the DEB Package
dpkg-deb -R package.deb extracted-package
2. Apply Changes
Modify files or scripts as needed in the extracted directory.
3. Rebuild the Package
dpkg-deb --build extracted-package
4. Test the Patched Package
Install and verify the functionality:
sudo dpkg -i package.deb
7. Golden Images
A golden image is a pre-configured template system image used for deploying systems quickly and consistently.
Golden Image Best Practices
- Start with a Minimal Base.
- Apply Customizations.
- Include Patches.
- Regular Updates.
- Validation.