LWM-Linux/08 - Advanced Linux Administration/Advanced Package Management (APT).md

Advanced Package Management with apt

1. Understanding apt

APT (Advanced Package Tool) is a powerful package management system used in Debian, Ubuntu, and other Debian-based Linux distributions. It simplifies the process of installing, upgrading, configuring, and removing software packages.

2. Key components

• apt: The command-line tool for package management
• apt-get: The older command-line tool (still widely used)
• apt-cache: Used for querying package information
• /etc/apt/sources.list: The main configuration file for package repositories

3. Basic apt commands

• Update package lists: sudo apt update
• Upgrade installed packages: sudo apt upgrade
• Install a package: sudo apt install package_name
• Remove a package: sudo apt remove package_name
• Search for a package: apt search keyword
• Show package information: apt show package_name

4. Advanced apt commands

a. Install specific version:

sudo apt install package_name=version_number

b. Downgrade a package:

sudo apt install package_name=older_version_number

c. Hold a package at its current version:

sudo apt-mark hold package_name

d. Remove a package and its configuration files:

sudo apt purge package_name

e. Remove unused dependencies:

sudo apt autoremove

f. Clean up the local repository:

sudo apt clean

g. Download a package without installing:

sudo apt download package_name

5. Working with repositories

a. Add a repository:

sudo add-apt-repository ppa:user/ppa-name

b. Remove a repository:

sudo add-apt-repository --remove ppa:user/ppa-name

c. Update package lists after adding/removing repositories:

sudo apt update

6. Managing package priorities

APT uses priorities to determine which version of a package to install when multiple versions are available. You can modify priorities using the /etc/apt/preferences file.

Example:

Package: firefox
Pin: release o=Ubuntu
Pin-Priority: 1001

This gives Firefox from the Ubuntu repositories a higher priority than other sources.

7. Apt configuration

The main configuration file is /etc/apt/apt.conf. You can create custom configuration files in /etc/apt/apt.conf.d/.

Example configuration options:

APT::Get::Show-Versions "true";
APT::Get::Show-Upgraded "true";

8. Troubleshooting

a. Fix broken dependencies:

sudo apt --fix-broken install

b. Reconfigure a package:

sudo dpkg-reconfigure package_name

c. Verify package integrity:

sudo apt-get check

9. Advanced features

a. Simulate installations:

sudo apt install -s package_name

b. Download source code:

sudo apt source package_name

c. Build a package from source:

sudo apt build-dep package_name
sudo apt source --compile package_name

d. Create a package download script:

sudo apt-get --print-uris --yes install package_name > download_script.sh

10. Best practices

• Regularly update and upgrade your system
• Use apt instead of apt-get for interactive use
• Be cautious when adding third-party repositories
• Always verify package names and versions before installation
• Use apt-mark to manage package states (hold, unhold, etc.)
• Regularly clean up unused packages and local repository cache