apt: why install older version of a package when newer is available via sources.list?
Question about why the `apt` package manager might install an older version of a package when a newer version is available from external sources. This can happen due to various reasons, and here's an explanation: 1. **Repository Priority**: The behavior of `apt` depends on the priority of repositories. Debian-based systems like Ubuntu use a system of priorities to determine which package versions to install. The distribution's official repositories typically have higher priority, and external or third-party repositories may have lower priority. 2. **Pin Priority**: You can assign pin priorities to specific repositories or packages using `/etc/apt/preferences` or `/etc/apt/preferences.d` files. These pinning preferences can override the default priorities set by `apt`. If you have such preferences set, it can influence which versions of packages are installed. 3. **Package Pinning**: Sometimes, specific package versions may be pinned to avoid conflicts or issues with other packa