U9fs is a program that serves Unix files to Plan 9 machines using the
9P protocol.  It is typically invoked on a Unix machine by inetd with
its standard input and output connected to a network connection,
typically TCP on an Ethernet.  It typically runs as user root and
multiplexes access to multiple Plan 9 clients over the single wire.
It assumes Plan 9 uids match Unix login names, and changes to the
corresponding Unix effective uid when processing requests.  U9fs
serves both 9P1 (the 9P protocol as used by the second and third
editions of Plan 9) and 9P2000.
