9P (or the Plan 9 Filesystem Protocol or Styx) is a

network protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroni ...

developed for the

Plan 9 from Bell Labs Plan 9 from Bell Labs is a distributed operating system which originated from the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s and built on UNIX concepts first developed there in the late 1960s. Since 2000, Plan 9 has b ...

distributed operating system A distributed operating system is system software over a collection of independent software, networked, communicating, and physically separate computational nodes. They handle jobs which are serviced by multiple CPUs. Each individual node holds a ...

as the means of connecting the components of a Plan 9 system. Files are key objects in Plan 9. They represent

windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

connections,

processes A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

, and almost anything else available in the operating system. 9P was revised for the 4th edition of Plan 9 under the name 9P2000, containing various improvements. Some of the improvements made are the removal of certain filename restrictions, the addition of a 'last modifier' metadata field for directories, and authentication files. The latest version of the Inferno operating system also uses 9P2000. The Inferno file protocol was originally called Styx, but technically it has always been a variant of 9P. A server implementation of 9P for Unix, called u9fs, is included in the Plan 9 distribution. A 9P

OS X macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...

client

kernel extension In computing, a loadable kernel module (LKM) is an object file that contains code to extend the running kernel, or so-called ''base kernel'', of an operating system. LKMs are typically used to add support for new hardware (as device drivers) and/o ...

is provided by Mac9P. A kernel client driver implementing 9P with some extensions for

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which i ...

is part of the v9fs project. 9P and its derivatives have also found application in embedded environments, such as the Styx on a Brick project.

Server applications

Many of Plan 9's applications take the form of 9P file servers. Examples include: *

acme Acme is Ancient Greek (ακμή; English transliteration: ''akmē'') for "the peak", "zenith" or "prime". It may refer to: Arts and entertainment * ''Acme'' (album), an album by the Jon Spencer Blues Explosion * Acme and Septimius, a fictional ...

: a text editor/development environment * rio: the Plan 9 windowing system *

plumber A plumber is a tradesperson who specializes in installing and maintaining systems used for potable (drinking) water, and for sewage and drainage in plumbing systems.

: interprocess communication * ftpfs: an FTP client that presents the files and directories on a remote FTP server in the local

namespace In computing, a namespace is a set of signs (''names'') that are used to identify and refer to objects of various kinds. A namespace ensures that all of a given set of objects have unique names so that they can be easily identified. Namespaces ...

* wikifs: a

wiki A wiki ( ) is an online hypertext publication collaboratively edited and managed by its own audience, using a web browser. A typical wiki contains multiple pages for the subjects or scope of the project, and could be either open to the pu ...

editing tool that presents a remote wiki as files in the local namespace * webfs: a file server that retrieves data from

URL A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifie ...

s and presents the contents and details of responses as files in the local namespace Outside of Plan 9, the 9P protocol is still used when a lightweight remote filesystem is required: *

NixOS NixOS is a Linux distribution built on top of the Nix package manager. It uses declarative configuration and allows reliable system upgrades. Several official package "channels" are offered, including the current Stable release and the Unstable ...

: a purely functional and declarative Linux distribution can rebuild itself inside a

virtual machine In computing, a virtual machine (VM) is the virtualization/ emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized har ...

, where the client uses 9P to mount the package store directory of the host. *

Windows Subsystem for Linux Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

: since Windows 10 version 1903, the subsystem implements 9P as a server and the host Windows operating system acts as a client. *

Crostini Crostini (meaning "little crusts" in Italian; singular ''crostino'') are an Italian appetizer consisting of small slices of grilled or toasted bread and toppings. The toppings may include a variety of different cheeses, meats, vegetables and ...

: a custom 9P server is used to provide access to files outside of a Linux VM *

QEMU QEMU is a free and open-source emulator (Quick EMUlator). It emulates the machine's processor through dynamic binary translation and provides a set of different hardware and device models for the machine, enabling it to run a variety of g ...

: the VirtFS device allows for filesystem sharing over 9P, which is accelerated with kernel drivers and shared memory
DIOD
Distributed I/O Daemon - a 9P file server

References

External links

9P Resources
page at cat-v.org
9P ManualThe Styx Architecture for Distributed Systems
by

Rob Pike Robert "Rob" Pike (born 1956) is a Canadian programmer and author. He is best known for his work on the Go programming language and at Bell Labs, where he was a member of the Unix team and was involved in the creation of the Plan 9 from Bell Labs ...

and Dennis Ritchie
The Organization of Networks in Plan 9
by Dave Presotto and Phil Winterbottom
Security in Plan 9
{{File systems Application layer protocols Inferno (operating system) Inter-process communication Internet Protocol based network software Network file systems Network file transfer protocols Network protocols Plan 9 from Bell Labs

Server applications

See also

References

External links