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32 .\" @(#)rwhod.8 8.2 (Berkeley) 12/11/93
33 .\" $FreeBSD: src/usr.sbin/rwhod/rwhod.8,v 1.13.2.4 2003/03/11 22:31:33 trhodes Exp $
40 .Nd system status server
50 utility is the server which maintains the database used by the
54 programs. Its operation is predicated on the ability to
58 messages on a network.
62 utility operates as both a producer and consumer of status information,
65 (listen mode) option is specified, in which case
66 it acts as a consumer only.
67 As a producer of information it periodically
68 queries the state of the system and constructs
69 status messages which are broadcasted or multicasted on a network.
70 As a consumer of information, it listens for other
72 servers' status messages, validating them, then recording
73 them in a collection of files located in the directory
78 option enables insecure mode, which causes
80 to ignore the source port on incoming packets.
88 interfaces. This is useful if you do not wish to keep dial on demand
89 interfaces permanently active.
93 option enables listen mode, which causes
95 to not broadcast any information.
96 This allows you to monitor other machines'
98 information, without broadcasting your own.
104 to use IP multicast (instead of
105 broadcast) on all interfaces that have
106 the IFF_MULTICAST flag set in their "ifnet" structs
107 (excluding the loopback interface). The multicast
108 reports are sent with a time-to-live of 1, to prevent
109 forwarding beyond the directly-connected subnet(s).
113 argument is supplied with the
117 will send IP multicast datagrams with a
120 via a SINGLE interface rather
123 must be between 0 and
124 32 (or MAX_MULTICAST_SCOPE). Note that
130 specifies transmission on one interface only.
136 argument, the program accepts multicast
138 reports from all multicast-capable interfaces. If a
140 argument is given, it accepts multicast reports from only one interface, the
141 one on which reports are sent (which may be controlled via the host's routing
142 table). Regardless of the
144 option, the program accepts broadcast or
145 unicast reports from all interfaces. Thus, this program will hear the
146 reports of old, non-multicasting
148 but, if multicasting is used,
151 won't hear the reports generated by this program.
153 The server transmits and receives messages at the port indicated
154 in the ``who'' service specification; see
156 The messages sent and received, are of the form:
157 .Bd -literal -offset indent
159 char out_line[8]; /* tty name */
160 char out_name[8]; /* user id */
161 long out_time; /* time on */
170 char wd_hostname[32];
174 struct outmp we_utmp;
176 } wd_we[1024 / sizeof (struct whoent)];
180 All fields are converted to network byte order prior to
181 transmission. The load averages are as calculated by the
183 program, and represent load averages over the 5, 10, and 15 minute
184 intervals prior to a server's transmission; they are multiplied by 100
185 for representation in an integer. The host name
186 included is that returned by the
188 system call, with any trailing domain name omitted.
189 The array at the end of the message contains information about
190 the users logged in to the sending machine. This information
191 includes the contents of the
193 entry for each non-idle terminal line and a value indicating the
194 time in seconds since a character was last received on the terminal line.
196 Messages received by the
198 server are discarded unless they originated at an
202 option was specified. In addition, if the host's name, as specified
203 in the message, contains any unprintable
206 message is discarded. Valid messages received by
208 are placed in files named
212 These files contain only the most recent message, in the
213 format described above.
215 Status messages are generated approximately once every
222 every 30 minutes to guard against
223 the possibility that this file is not the system
224 image currently operating.
229 Status information should be sent only upon request rather than continuously.
230 People often interpret the server dying
231 or network communication failures
232 as a machine going down.