rwhod man page on FreeBSD

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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 period‐
     ically 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
	     information, 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 mul‐
	     ticast 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 con‐
	     trolled 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 inte‐
     ger.  The host name included is that returned by the gethostname(3) 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 or the -i option was specified.  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.	The
     rwhod utility performs an nlist(3) on /boot/kernel/kernel every 30 min‐
     utes 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 continu‐
     ously.  People often interpret the server dying or network communication
     failures as a machine going down.

BSD			       December 11, 1993			   BSD
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