RWHOD(8)		  BSD System Manager's Manual		      RWHOD(8)

NAME
     rwhod — system status server

SYNOPSIS
     rwhod

DESCRIPTION
     Rwhod is the server which maintains the database used by the rwho(1) and
     ruptime(1) programs.  Its operation is predicated on the ability to
     broadcast messages on a network.

     Rwhod operates as both a producer and consumer of status information.  As
     a producer of information it periodically queries the state of the system
     and constructs status messages which are broadcast on a network.  As a
     consumer of information, it listens for other rwhod servers' status mes‐
     sages, validating them, then recording them in a collection of files
     located in the directory /var/rwho.

     The server transmits and receives messages at the port indicated in the
     ``rwho'' service specification; see services(5).  The messages sent and
     received, are of the form:

	   struct  outmp {
		   char	   out_line[8];		   /* tty name */
		   char	   out_name[8];		   /* user id */
		   long	   out_time;		   /* time on */
	   };

	   struct  whod {
		   char	   wd_vers;
		   char	   wd_type;
		   char	   wd_fill[2];
		   int	   wd_sendtime;
		   int	   wd_recvtime;
		   char	   wd_hostname[32];
		   int	   wd_loadav[3];
		   int	   wd_boottime;
		   struct  whoent {
			   struct  outmp we_utmp;
			   int	   we_idle;
		   } wd_we[1024 / sizeof (struct whoent)];
	   };

     All fields are converted to network byte order prior to transmission.
     The load averages are as calculated by the w(1) program, and represent
     load averages over the 5, 10, and 15 minute intervals prior to a server's
     transmission; they are multiplied by 100 for representation in an inte‐
     ger.  The host name included is that returned by the gethostname(2) sys‐
     tem call, with any trailing domain name omitted.  The array at the end of
     the message contains information about the users logged in to the sending
     machine.  This information includes the contents of the utmp(5) entry for
     each non-idle terminal line and a value indicating the time in seconds
     since a character was last received on the terminal line.

     Messages received by the rwho server are discarded unless they originated
     at an rwho server's port.	In addition, if the host's name, as specified
     in the message, contains any unprintable ASCII characters, the message is
     discarded.	 Valid messages received by rwhod are placed in files named
     whod.hostname in the directory /var/rwho.	These files contain only the
     most recent message, in the format described above.

     Status messages are generated approximately once every 3 minutes.	Rwhod
     performs an nlist(3) on /vmunix every 30 minutes to guard against the
     possibility that this file is not the system image currently operating.

SEE ALSO
     rwho(1), ruptime(1)

BUGS
     There should be a way to relay status information between networks.  Sta‐
     tus information should be sent only upon request rather than continu‐
     ously.  People often interpret the server dying or network communication
     failures as a machine going down.

HISTORY
     The rwhod command appeared in 4.2BSD.

4.2 Berkeley Distribution      December 11, 1993     4.2 Berkeley Distribution

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