History of free and open-source software like Unix, Torvalds' kernel attracted attention from volunteer programmers. Until this point, the GNU project's lack of a kernel meant that no complete free software operating systems existed. The development of Torvalds' kernel closed that last gap. The combination of the almost-finished GNU operating system and the Linux kernel made the first complete free software operating system. Among Linux distributions, Debian GNU/Linux, begun by Ian Murdock in 1993, is noteworthy for being explicitly committed to the GNU and FSF principles of free software. The Debian developers' principles are expressed in the Debian Social Contract. Since its inception, the Debian project
Fedora (operating system) installed using the DNF package manager or GNOME Software. Additionally, extra repositories can be added to the system, so that software not available in Fedora can be installed easily. Software that is not available via official Fedora repositories, either because it doesn't meet Fedora's definition of free software or because its distribution may violate US law, can be installed using third-party repositories. Popular third-party repositories include RPM Fusion free and non-free repositories. Fedora also provides users with an easy-to-use build system for creating their own repositories called Copr. Since the release of Fedora 25, the operating system defaults to the