パッケージ管理（Debian/Ubuntu）：`apt`、`dpkg`

Welcome to package management! On Linux, software comes in packages. These are archives containing program files, documentation, and metadata.

A package manager is a tool that automates the installation, upgrade, configuration, and removal of software. It handles dependencies, ensuring all necessary components are installed.

On Debian-based systems (like Ubuntu), the fundamental tool for managing packages is dpkg. It's a low-level tool that directly interacts with .deb files (Debian package files).

• dpkg installs, removes, and manages individual .deb packages.
• It does NOT automatically handle dependencies. If a package needs others, you must install them yourself.

To install a .deb file you've downloaded, you use the -i (or --install) option with dpkg.

Remember, if the package has dependencies, dpkg will warn you and the installation might fail or be incomplete until those dependencies are met.

You can query dpkg to see information about installed packages. The -l (or --list) option shows all installed packages.

You can pipe its output to grep to search for specific packages.

While dpkg handles individual .deb files, apt (Advanced Package Tool) is the user-friendly, high-level front-end. It works with repositories (servers holding many packages).

apt automatically handles dependencies, fetches packages from repositories, and simplifies system-wide updates.

Before installing or upgrading, you should always run apt update. This command downloads the latest package information from the configured repositories.

It does NOT install new software or update existing ones, it only updates the list of what's available.

To install new software from the repositories, use apt install followed by the package name. apt will resolve and install all necessary dependencies.

You'll be prompted to confirm the installation before it proceeds.

To upgrade all installed packages to their latest available versions (based on your updated package lists), use apt upgrade.

This is crucial for security updates and new features. It's a good practice to run apt update before apt upgrade.

When you no longer need a package, you can remove it using apt remove or apt purge.

• apt remove package_name: Deletes the package but keeps its configuration files.
• apt purge package_name: Deletes the package AND its configuration files, for a cleaner uninstall.

You've learned about the two main package management tools on Debian-based systems. Let's test your understanding!

Great job! You've learned about Debian's powerful package management system:

• dpkg: The low-level tool for individual .deb files, without dependency resolution.
• apt: The high-level, user-friendly tool for managing packages from repositories, handling dependencies automatically.

Key apt commands include update, install, upgrade, remove, and purge.