Software Upgrade Protocol implementation

 The SUP System is a set of programs developed by Carnegie Mellon
 University that provide for collections of files to be maintained in
 identical versions across a number of machines. These programs are:
 .
 SUP: The "client" program, run by users or system maintainers, which
 initiates the upgrade activity on a machine requesting the
 latest version of a collection of files. SUP will normally be
 run as a daemon, firing up once each night (week, etc.) to
 upgrade the specified file collections.
 .
 SUPFILESRV: The "file server" program, a daemon that is run by the
 system maintainer to service requests for files initiated by client
 SUP programs. The file server runs on every machine used as a
 "repository" of distributable versions of files. It runs continuously
 and listens for network connection requests by individual client
 processes; for each individual client request, a process is forked to
 service that request.
 .
 SUPSCAN: The "file scanner" program, that may optionally be run
 periodically to speed up execution of the file server. It
 pre-compiles a list of files on the file system that match the
 specifications for a given file collection so that the file server
 need not do this during each upgrade of that collection. The file
 scanner is normally used daily for very large file collections that
 are upgraded by many clients each day; it is not so useful for small
 file collections or for those that are upgraded by only a few client
 machines per day.