Plan 9 Official
Plan 9 from Bell Labs is a distributed operating system, primarily used as a research vehicle. It was developed as the research successor to Unix by the Computing Sciences Research Center at Bell Labs between the mid-1980s and 2002. Plan 9 is most notable for representing all system interfaces, including those required for networking and the user-interface, through the filesystem rather than specialized interfaces. Plan 9 aims to provide users with a workstation-independent working environment through the use of the 9P protocols. Plan 9 continues to be used and developed in some circles as a research operating system and by hobbyists.
The name "Plan 9 from Bell Labs" is a reference to the classic science fiction B-movie Plan 9 from Outer Space.
Plan 9 replaced Unix at Bell Labs as the organization's primary platform for research and explores several changes to the original Unix model that improve the experience of using and programming the system, notably in distributed multi-user environments. Plan 9 was a Bell Labs internal project from its start during the mid 1980s. In 1992, the first public release was made available to universities. In 1995, a commercial second release version was made available to the general public. In the late 1990s, Lucent Technologies, who had inherited Bell Labs, dropped commercial interest in the project. In 2000, a non-commercial third release was made under an open source license. In 2002, a non-commercial fourth release was made under a new free software license.
A user and development community, including current and former Bell Labs and MIT members, continues to produce daily minor releases as ISO images. Bell Labs still hosts development. The development source tree is accessible over the 9P and HTTP protocols and is used to keep an installation up to date.