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

     rwhod -- system status server

     rwhod [-bpa] [-u user]

     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 lo-
     cated in the directory /var/spool/rwho.

     The server	transmits and receives messages	at the port indicated in the
     ``rwho'' service specification; see services(5).

     If	the -b flag is supplied, only broadcast	interfaces, such as ethernets,
     will be used.  If the -p flag is supplied,	only point-to-point interfaces
     will be used. If the -a flag is supplied, or no flags are supplied, all
     interfaces	will be	used.

     If	the -u flag is supplied, rwhod will run	as the specified user instead
     of	as root.

     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/spool/rwho.  These files contain only
     the most recent message, in the format described above.

     Status messages are generated approximately once every 3 minutes.	Rwhod
     recomputes	the system boot	time every 30 minutes because on some (non-
     Linux) systems it is not a	totally	reliable process.

     rwho(1), ruptime(1)

     There should be a way to relay status information between networks.  Peo-
     ple often interpret the server dying or network communtication failures
     as	a machine going	down.

     The rwhod command appeared	in 4.2BSD.

Linux NetKit (0.17)		 May 13, 1997		   Linux NetKit	(0.17)


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