# Plan 9 from Bell Labs - 4th Edition Source Tree

This repository contains the final public release of **Plan 9 from Bell Labs**. It
was originally distributed by Bell Labs and is now provided by the Plan 9
Foundation under open source licenses. The distribution preserves the operating
system as it existed in the early 2000s and is mainly of historical and
research interest.

The original release notes for this edition can be found in
`/sys/doc/release4.ms`.

## Directory Overview

- **386**, **amd64**, **arm**, **mips**, **power**, **power64**, **sparc** –
  Architecture-specific kernels, libraries and binaries.
- **acme** – Source for the `acme` editor and its related tools.
- **adm** – System administration utilities and scripts.
- **cfg** – Example configuration files.
- **cron** – Files for the `cron` scheduler service.
- **dist** – Scripts and files used to build distribution images.
- **lib** – Shared data such as fonts, dictionaries and other resources.
- **mail** – The `upas` mail system.
- **rc** – Scripts for the Plan 9 `rc` shell and boot environment.
- **sys** – System documentation, manual pages and the bulk of source code
  including the kernel and userland commands.
- **usr/glenda** – Example user environment with introductory notes.

## Building

Compiling the entire operating system requires a running Plan 9 environment with
its `mk` build tool. On Unix-like hosts one commonly builds the **drawterm**
client, which allows connecting to a Plan 9 CPU server. To build drawterm:

```bash
cd sys/src/cmd/unix/drawterm
make CONF=unix
```

This requires standard development tools and X11 headers.

## Licensing

Plan 9 is released under the Lucent Public License 1.02 along with a collection
of other licenses for specific components (see the `LICENSE*` files and
`NOTICE`). Some assets such as fonts retain copyright to their respective
owners and were included by permission.