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Preface to the Fourth (2002) Edition
Plan 9 continues to grow and adapt. The fourth major release of the system
incorporates a number of changes, but the most central is the conversion
to a new version of the 9P file system protocol. This new version was
motivated by a desire to support files with name elements longer than 27
bytes (the old NAMELEN), but the opportunity was taken to change a number
of other things about the protocol, making it more efficient, more
flexible, and easier to encapsulate. One simple but indispensable new
feature made possible by the protocol change is that the system now
records the user who last modified a file; try ls -m to identify the
Many aspects of system security have been improved. The new security agent
factotum(4) maintains user passwords, while secstore(8) keeps them safe
and enables single sign-on to multiple domains and machines using a
variety of secure protocols and services.
Throughout the system, components have been rewritten and interfaces
modified to eliminate restrictions, improve performance, and clarify
design. The full list is too long to include here, but significant changes
have occurred in a number of system calls (wait(2), stat(2), mount(2), and
errstr(2)), the thread library (thread(2)), formatted printing (print(2)
and fmtinstall(2)), security (many pages in section 2, including auth(2),
authsrv(2)), and many others.
The changes are sweeping and are accompanied by many new programs, tools,
services, and libraries. See the manual pages and the accompanying
documents for more information.
Murray Hill NJ
Copyright (c) 2002
Lucent Technologies Inc.
All rights reserved.