Plan 9

Glenda, the Plan 9 Mascot

Plan 9 from Bell Labs is a research OS family, created at Bell Labs by many of the same people who created UNIX, like Ken Thompson, Dennis Ritchie and Rob Pike. It's distinguishing features include the use of files with the 9P protocol for most, if not all resources in the operating system (including graphics), and private namespaces, where each process can have a different view of the file system. Interest in Plan 9 stems out of curiosity, admiration and sometimes idealism.

Licensing

The First and Second Editions of Plan 9 were only available to universities and then for an exorbitant fee. The Third Edition of Plan 9 was released under the Plan 9 Licence in 2000, which Richard Stallman considered non-free. The Fourth Edition was released under the Lucent Public Licence in 2002 which the FSF does consider free but not GPL-compatible, along with the distribution becoming openly developed and updated daily. In 2014 Plan 9 was relicenced under GPLv2 for UCB's Akaros operating system (to much dislike).

Distributions

• Plan 9 from Bell Labs, the Fourth Edition, where development is almost dead.

• 9legacy, which is several patches on top of the Bell Labs distribution.

• 9atom is Erik Quanstrom's personal fork of Plan 9. It augments the Plan 9 distribution with the addition of a 386 PAE kernel, an amd64 cpu and terminal kernel, the nupas mail file system, extra PC hardware support, IL and Ken's fs.

• Inferno is a distributed operating system started at Bell Labs, but is now developed and maintained by Vita Nuova Holdings as free software.

• 9front is an active, community-led fork of Plan 9, the life and breath of Plan 9 development, including new advancements such as better hardware support, audio, wireless networking and new programs like NES, SNES, Game Boy, GBA and Genesis emulators and a paint program. If you want to run Plan 9, this is probably the way to go.

Programs

It should be noted there are few choices of software for Plan 9, maybe owing to lack of users but also to how good the software actually is.

Web browser

Two really feasible options for web browsing exist on Plan 9:

• Mothra - a very fast and simple web browser (or rather, a web document reader). Under the hood it uses the webfs interface. It supports only HTML and images.
• Abaco - a web browser that looks like acme. It does a bit of CSS, but still no JavaScript.

Text editor

• Sam - a minimal text editor that makes use of Standard Regular Expressions.
• Acme - Emacs done right, a programming environment that makes heavy use of the mouse and that can be used as a mail client with upas.
• ed - a venerable text editor.

The rc shell

Plan 9's default shell is the rc shell, designed by Tom Duff. It's constructs are similar to UNIX's Bourne shell but are somewhat syntactically different. The most important thing to get around in your head is how programs in subdirectories of /bin (where many different directories are actually bound) are executed. Acme will most likely be placed in /bin, so a simple

% acme

will do. Now, this is a rather contrived example, but let's assume we have a new disk and we want to run fdisk on it.

% fdisk

won't work, because fdisk is actually in /bin/disk/fdisk (it's probably really in /386/bin/disk/fdisk). So you would need to run

% disk/fdisk

A better example is if you cannot wrap your head around rc, and you really want your curmudgeonlike UNIX shell, you would run

% ape/sh

because sh is in the ape (ANSI POSIX Environment) folder.

Further reading

• Plan 9's Wikipedia page - The history of Plan 9 and a lot of the concepts used.
• 9front's Frequently Questioned Answers - A document that somewhat copies the structure of the OpenBSD FAQ that explains how to do quite a lot of things with 9front and Plan 9. A lot of this page is plagiarised inspired by this document.
• cat-v.org - A museum dedicated to technology, philosophy and politics, formerly curated by Uriel.