rwhod man page on BSDOS

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

NAME
     rwhod - system status server

SYNOPSIS
     rwhod
     rwhod -m
     rwhod -M ttl

DESCRIPTION
     The rwhod server maintains the database used by the rwho(1) and rup-
     time(1) programs.	Its operation is predicated on the ability to
     broadcast or multicast messages on a network.

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

     The -m and -M flags configure rwhod to use multicast rather than broad-
     cast.  Under -m, rwhod sends its multicast message to all multicast-capa-
     ble interfaces (those with IFF_MULTICAST set in their flags; see
     ifconfig(8)).  In this case the time-to-live is fixed at 1, preventing
     the multicast from being forwarded beyond any directly-connected subnets.
     With -M, rwhod sends its multicast message with the given ttl as its time
     to live, but to the ``whod'' group (224.0.1.3) rather than individually
     to each interface.	 This is intended to be used with a multicast router
     which will distribute the message to members of the multicast group.

     In any mode, broadcast or multicast, rwhod will accept all forms of re-
     ports.  This means that if broadcast and multicast rwhod servers are com-
     bined on one network, the multicast-capable systems will see everyone,
     while the broadcast-only machines will see only each other.

     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.

SEE ALSO
     mrouted(8),  rwho(1),  ruptime(1)

BUGS
     Status 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. The multicast additions are from
     Stanford University.

4.2 Berkeley Distribution      December 11, 1993			     2
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