Gentoo Linux

Gentoo's Portage package manager compiles software from source at install time rather than fetching a pre-built binary, letting a user enable or disable specific compile-time features ('USE flags') per package -- strip out unwanted dependencies, enable hardware-specific optimizations, or build with support for exactly the features actually needed and nothing else. This gives Gentoo installations a level of customization no binary-package distribution can match, at the direct cost of significantly longer install and update times, since packages need to actually compile rather than just download. It's a rolling-release distribution at heart, and its documentation and configuration philosophy have influenced several other source-based or highly-customizable projects, including Pentoo (its security-focused derivative) and Funtoo (an independent fork).