This is a re-release of the final version of the 4th Edition of Plan 9
from Bell Labs distributed directly by Bell Labs.
4th Edition was originally released by Lucent Technologies in 2002. It
was released under the terms the Lucent Public License Version 1.02.
4th Edition continues the development of the same ideas, but in many
ways represents the base of what most people think of as "modern" Plan
9 today. The ubiquitous file protocol, 9P, got its first revision, to
9P2000, which caused changes to many parts of the system. It also saw
the debut of venti(8) and fossil(4), which began replacing the
venerable old file server, fs(4). Authentication largely moved to a
separate agent, factotum(4). Updates moved to replica, and the wiki
was created. The original release notes for this edition can be found
While this release is a recognizable ancestor of the latest Plan 9
available, it is still quite old, and this release is mostly for
educational and research purposes. The file protocol and
authentication mechanisms are continued in modern Plan 9, though, so
researchers looking to run this should have an easier time than with
all previous releases. This is a second release of the 4th Edition,
marking the final state of Plan 9 as distributed directly by Bell
The only changes between this release and the original 4th Edition
release are the new NOTICE, LICENSE, and README files, and moving the
old ones. In particular, any copyright notices attributing things to
Lucent Technologies or Bell Labs, or notices on restrictions of their
use, should be read as historical; all such rights have been
transferred to the Plan 9 Foundation and released as open source.
Parts (notably, the fonts) maintain trademark and copyright to their
respective parties (such as Bigelow & Holmes Inc.) and were included
in Plan 9 by permission; those copyrights are unaffected by the
transfer to Plan 9 Foundation and remain in effect per the terms found
in this distribution.