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

NAME

     rwhod -- system status server

SYNOPSIS

     rwhod [-i] [-p] [-l] [-m [ttl]]

DESCRIPTION

     The rwhod utility 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 or multicast messages on a network.

     The rwhod utility operates as both a producer and consumer of status information, unless the -l (listen mode) option is specified, in which
     case it acts as a consumer only.  As a producer of information it periodically queries the state of the system and constructs status messages
     which are broadcasted or multicasted on a network.  As a consumer of information, it listens for other rwhod servers' status messages, vali-
     dating them, then recording them in a collection of files located in the directory /var/rwho.

     The following options are available:

     -i      Enable insecure mode, which causes rwhod to ignore the source port on incoming packets.

     -p      Ignore all POINTOPOINT interfaces.  This is useful if you do not wish to keep dial on demand interfaces permanently active.

     -l      Enable listen mode, which causes rwhod to not broadcast any information.  This allows you to monitor other machines' rwhod informa-
	     tion, without broadcasting your own.

     -m [ttl]
	     Cause rwhod to use IP multicast (instead of broadcast) on all interfaces that have the IFF_MULTICAST flag set in their "ifnet"
	     structs (excluding the loopback interface).  The multicast reports are sent with a time-to-live of 1, to prevent forwarding beyond
	     the directly-connected subnet(s).

	     If the optional ttl argument is supplied with the -m flag, rwhod will send IP multicast datagrams with a time-to-live of ttl, via a
	     SINGLE interface rather than all interfaces.  ttl must be between 0 and 32 (or MAX_MULTICAST_SCOPE).  Note that -m 1 is different
	     from -m, in that -m 1 specifies transmission on one interface only.

	     When -m is used without a ttl argument, the program accepts multicast rwhod reports from all multicast-capable interfaces.  If a ttl
	     argument is given, it accepts multicast reports from only one interface, the one on which reports are sent (which may be controlled
	     via the host's routing table).  Regardless of the -m option, the program accepts broadcast or unicast reports from all interfaces.
	     Thus, this program will hear the reports of old, non-multicasting rwhods, but, if multicasting is used, those old rwhods will not
	     hear the reports generated by this program.

     The server transmits and receives messages at the port indicated in the ``who'' 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
     integer.  The host name included is that returned by the gethostname(3) system 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
     entry from the user accounting database 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 or the -i option was specified.  In addi-
     tion, 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.	The rwhod utility performs an nlist(3) on /boot/kernel/kernel every 30
     minutes to guard against the possibility that this file is not the system image currently operating.

SEE ALSO

     ruptime(1), rwho(1)

HISTORY

     The rwhod utility appeared in 4.2BSD.

BUGS

     Status information should be sent only upon request rather than continuously.  People often interpret the server dying or network communica-
     tion failures as a machine going down.

BSD
								 January 21, 2010							       BSD