# Plan 9

> distributed operating system designed by Bell Labs as an UNIX's intended successor

**Wikidata**: [Q725779](https://www.wikidata.org/wiki/Q725779)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Plan_9_from_Bell_Labs)  
**Source**: https://4ort.xyz/entity/plan-9

## Summary
Plan 9 is a distributed operating system developed by Bell Labs as the intended successor to the Unix operating system. It is designed to operate across multiple systems over a network, organizing all resources into a unified hierarchical namespace.

## Key Facts
- **Developer:** Bell Labs (headquartered in Murray Hill, New Jersey).
- **Initial Release:** 1992 (First Edition).
- **Class:** Distributed operating system and free/open-source software.
- **Key Contributors:** Rob Pike and Dennis M. Ritchie.
- **Mascot:** Glenda.
- **Current License:** MIT License (since March 23, 2021).
- **Stable Version:** Fourth Edition, released in 2002.
- **Hardware Support:** MIPS, DEC Alpha, PowerPC, SPARC, ARM (A32, A64), and x86 architectures.
- **Copyright Holder:** Plan 9 Foundation (as of March 2021).

## FAQs
### Q: What is the primary purpose of Plan 9?
A: Plan 9 was designed by Bell Labs to be a distributed successor to Unix, capable of managing resources across multiple networked computers as if they were a single system.

### Q: Is Plan 9 open source?
A: Yes. While it originally used the Lucent Public License and later the GPL v2, it has been available under the MIT License since March 2021.

### Q: What software or systems were inspired by Plan 9?
A: Plan 9 influenced several projects, including the Inferno operating system, 9front, Harvey OS, and Plan B.

### Q: Who are the notable people associated with its development?
A: The system was developed by a team at Bell Labs that included software engineer Rob Pike and Unix co-inventor Dennis M. Ritchie.

## Why It Matters
Plan 9 represents a major architectural shift in operating system design, moving from the standalone model of Unix to a fully distributed environment. Developed by the same research group at Bell Labs that created Unix and C, it sought to address the limitations of networking by treating all system resources—such as processes, hardware devices, and network connections—as files. 

This "everything is a file" philosophy allows for a seamless interface where local and remote resources are accessed identically. Although it did not achieve the same commercial ubiquity as its predecessor, Plan 9's innovations in distributed computing and its 9P protocol have had a lasting impact on computer science research. Its transition to the Plan 9 Foundation and the MIT License ensures that its source code remains a vital resource for developers and researchers exploring alternative OS architectures.

## Notable For
- **Distributed Architecture:** Built from the ground up to function across a network of multiple machines.
- **Unified Namespace:** Extends the Unix "everything is a file" concept to all system resources across a network.
- **Historical Pedigree:** Created by the inventors of Unix and C at Bell Labs.
- **Naming Origin:** Named after the cult science fiction film *Plan 9 from Outer Space*.
- **Mascot:** Features a distinct mascot named Glenda.

## Body

### Development and Versions
Plan 9 was developed at Bell Labs in Murray Hill, New Jersey, as a research project to succeed Unix. The development team included prominent computer scientists such as Rob Pike and Dennis M. Ritchie.
- **First Edition (1992):** The initial public release.
- **Second Edition (1995):** Follow-up release.
- **Third Edition (2000):** Released at the turn of the millennium.
- **Fourth Edition (2002):** The final major stable release from Bell Labs.

### Technical Architecture
As a distributed operating system, Plan 9 allows users to access resources on different physical machines transparently.
- **Programming Language:** The system is primarily written in C.
- **GUI Frameworks:** It utilizes the 8½ and rio windowing systems.
- **Platforms:** It supports a wide range of architectures, including MIPS, DEC Alpha, PowerPC, SPARC, and ARM.
- **Security:** A known kernel vulnerability is documented as CVE-2007-1189.

### Licensing and Governance
The ownership and licensing of Plan 9 have evolved significantly over three decades:
- **Lucent Public License:** Applied starting April 29, 2002.
- **GNU GPL v2:** Applied starting February 14, 2014.
- **MIT License:** Applied starting March 23, 2021, following the transfer of copyright from Bell Labs to the Plan 9 Foundation.

### Derivative Works and Legacy
Plan 9 served as the foundation for several other operating systems and software projects:
- **Inferno:** A distributed OS based on Plan 9 technology.
- **9front:** A community-maintained distributed operating system.
- **Plan 9 from User Space:** A port of Plan 9 libraries and applications to Unix-like operating systems.
- **Other Derivatives:** Includes Harvey OS, Plan B, and 9base.

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## References

1. [Source](https://p9f.org/about.html)
2. [Source](https://9p.io/plan9/about.html)
3. Freebase Data Dumps. 2013
4. [Source](https://www.bell-labs.com/institute/blog/plan-9-bell-labs-cyberspace/)