How does adding repositories work internally in Linux?

In Linux, adding repositories is a way to extend the package management capabilities of your system. Repositories are collections of software packages stored on remote servers. When a user adds a repository, they are essentially informing the package manager where to look for software updates and additional packages that can be installed on the system. Here’s how it works internally:

1. Repository Definition: Each repository is defined in a configuration file. For example, on Debian-based systems, this is typically done in the /etc/apt/sources.list file or in individual files under the /etc/apt/sources.list.d/ directory.
2. Package Metadata: Repositories provide package metadata, which includes information about available packages, their versions, and dependencies. This metadata allows the package manager to resolve dependencies and determine which packages need to be installed or updated.
3. Package Manager Commands: When a user runs commands like apt update or dnf update, the package manager downloads the latest metadata from the defined repositories. This process informs the package manager of newly available software, updates, or removals.
4. Installation Process: When installing a package, the package manager checks the repositories for the required software and its dependencies, downloading them as needed.

Example command to add a repository in a Debian-based system: