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+.\" Copyright (c) 1983, 1991, 1993
+.\" The Regents of the University of California. All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\" must display the following acknowledgement:
+.\" This product includes software developed by the University of
+.\" California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\" may be used to endorse or promote products derived from this software
+.\" without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" @(#)rwhod.8 8.2 (Berkeley) 12/11/93
+.\"
+.Dd December 11, 1993
+.Dt RWHOD 8
+.Os BSD 4.2
+.Sh NAME
+.Nm rwhod
+.Nd system status server
+.Sh SYNOPSIS
+.Nm rwhod
+.Sh DESCRIPTION
+.Nm Rwhod
+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
+.Nm 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
+.Nm rwhod
+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 ``rwho'' 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 */
+ 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)];
+};
+.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 2
+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
+.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
+server are discarded unless they originated at an
+.Xr 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 rwhod
+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.
+.Nm Rwhod
+performs an
+.Xr nlist 3
+on
+.Pa /vmunix
+every 30 minutes to guard against
+the possibility that this file is not the system
+image currently operating.
+.Sh SEE ALSO
+.Xr rwho 1 ,
+.Xr ruptime 1
+.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.
+.Sh HISTORY
+The
+.Nm
+command appeared in
+.Bx 4.2 .
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