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.\"     from: @(#)rwhod.8	8.2 (Berkeley) 12/11/93
.\"	$NetBSD: rwhod.8,v 1.16 2005/07/01 16:18:46 peter Exp $
.\"
.Dd July 1, 2005
.Dt RWHOD 8
.Os
.Sh NAME
.Nm rwhod
.Nd system status server
.Sh SYNOPSIS
.Nm
.Op Fl i Ar interval
.Sh DESCRIPTION
.Nm
is the server which maintains the database used by the
.Xr rwho 1
and
.Xr ruptime 1
programs.  Its operation is predicated on the ability to
.Em broadcast
messages on a network.
.Pp
The following option is available:
.Bl -tag -width XXXXXXXXXXX
.It Fl i Ar interval
Allows for the broadcast interval to be changed from the default 3 minutes.
The
.Ar time
argument is the number of seconds to change the interval to, or if the
value is suffixed by
.Dq m
then it is interpreted as minutes.
The maximum allowed value for the broadcast interval is 11 minutes
because higher values will cause
.Xr ruptime 1
to mark the host as being down.
.Pp
.El
.Nm
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
.Nm
servers' status messages, validating them, then recording
them in a collection of files located in the directory
.Pa /var/rwho .
.Pp
The server transmits and receives messages at the port indicated
in the ``who'' service specification; see
.Xr services 5 .
The messages sent and received, are of the form:
.Bd -literal -offset indent
struct	outmp {
	char	out_line[8];		/* tty name */
	char	out_name[8];		/* user id */
	int32_t	out_time;		/* time on */
};

struct	whod {
	char	wd_vers;
	char	wd_type;
	char	wd_fill[2];
	int32_t	wd_sendtime;
	int32_t	wd_recvtime;
	char	wd_hostname[32];
	int32_t	wd_loadav[3];
	int32_t	wd_boottime;
	struct	whoent {
		struct	outmp we_utmp;
		int32_t	we_idle;
	} wd_we[1024 / sizeof (struct whoent)];
};
.Ed
.Pp
All fields are converted to network byte order prior to
transmission.  The load averages are as calculated by the
.Xr 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
.Xr gethostname 3
function 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
.Xr 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.
.Pp
Messages received by the
.Xr rwho 1
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
.Tn ASCII
characters, the
message is discarded.  Valid messages received by
.Nm
are placed in files named
.Pa whod.hostname
in the directory
.Pa /var/rwho .
These files contain only the most recent message, in the
format described above.
.Pp
Status messages are generated approximately once every
3 minutes.
.Sh SEE ALSO
.Xr ruptime 1 ,
.Xr rwho 1
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .
.Sh BUGS
There should be a way to relay status information between networks.
Status information should be sent only upon request rather than continuously.
People often interpret the server dying
or network communication failures
as a machine going down.