9P (protocol)

9P (or the Plan 9 Filesystem Protocol or Styx), is a network protocol developed for the Plan 9 from Bell Labs distributed operating system as the means of connecting the components of a Plan 9 system. Files are key objects in Plan 9. They represent windows, network connections, processes, and almost anything else available in the operating system. 9P encourages caching and also serving of synthetic files (e.g. /proc to represent processes), unlike NFS.

9P was revised for the 4th edition of Plan 9 under the name 9P2000 that contained various fundamental improvements. The latest version of Inferno also uses 9P2000. The Inferno file protocol was originally called Styx, but technically it has always been a variant of 9P.

There is a server implementation of 9P for Unix called u9fs included in the Plan 9 distribution, and a kernel client driver for Linux as part of the v9fs project. 9P (and derivatives) have also found application in embedded environments, such as the Styx on a Brick project.

9P server applications

Many of Plan 9's applications take the form of 9P servers; some particularly noteworthy examples:

• acme: a user interface for programmers
• rio: the Plan 9 window manager.
• plumber: interprocess communication
• wikifs: a wiki

See also

• v9fs - u9fs: 9P implementation for Unix-like operating systems
• IL Protocol - Transport protocol that was designed for 9P in local area networks.
• distributed file system

External links

• 9P Resources page at cat-v.org

Documentation

• 9P Manual
• The Styx Architecture for Distributed Systems by Rob Pike and Dennis Ritchie
• The Organization of Networks in Plan 9 by Dave Presotto and Phil Winterbottom

Implementations

• 9P server and client implementations in Python
• 9P server and client implementations in Java
• Ruby-IXP 9P client implemented in Ruby for wmii
• 9P client implemenations in Tcl
• 9P server and client implementation in C under the BSD license (part of the wmii project)
• 9P client implementation in Common Lisp
• 9pclient library - A 9P library in C (part of the Plan 9 from User Space project)
• Styx server and client implementations in Limbo (part of the Inferno operating system)