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28 .\" @(#)rwhod.8 8.2 (Berkeley) 12/11/93
29 .\" $FreeBSD: src/usr.sbin/rwhod/rwhod.8,v 1.13.2.4 2003/03/11 22:31:33 trhodes Exp $
31 .Dd September 11, 2019
36 .Nd system status server
47 utility is the server which maintains the database used by the
51 programs. Its operation is predicated on the ability to
55 messages on a network.
59 utility operates as both a producer and consumer of status information,
62 (listen mode) option is specified, in which case
63 it acts as a consumer only.
64 As a producer of information it periodically
65 queries the state of the system and constructs
66 status messages which are broadcasted or multicasted on a network.
67 As a consumer of information, it listens for other
69 servers' status messages, validating them, then recording
70 them in a collection of files located in the directory
75 option enables insecure mode, which causes
77 to ignore the source port on incoming packets.
81 option allows for the broadcast
85 to be reduced below 3 minutes. This enables for more 'real' time statistics
89 operand can be given as 30 (30 seconds) or 1m (1 minute), for example.
97 interfaces. This is useful if you do not wish to keep dial on demand
98 interfaces permanently active.
102 option enables listen mode, which causes
104 to not broadcast any information.
105 This allows you to monitor other machines'
107 information, without broadcasting your own.
113 to use IP multicast (instead of
114 broadcast) on all interfaces that have
115 the IFF_MULTICAST flag set in their "ifnet" structs
116 (excluding the loopback interface). The multicast
117 reports are sent with a time-to-live of 1, to prevent
118 forwarding beyond the directly-connected subnet(s).
122 argument is supplied with the
126 will send IP multicast datagrams with a
129 via a SINGLE interface rather
132 must be between 0 and
133 32 (or MAX_MULTICAST_SCOPE). Note that
139 specifies transmission on one interface only.
145 argument, the program accepts multicast
147 reports from all multicast-capable interfaces. If a
149 argument is given, it accepts multicast reports from only one interface, the
150 one on which reports are sent (which may be controlled via the host's routing
151 table). Regardless of the
153 option, the program accepts broadcast or
154 unicast reports from all interfaces. Thus, this program will hear the
155 reports of old, non-multicasting
157 but, if multicasting is used,
160 won't hear the reports generated by this program.
162 The server transmits and receives messages at the port indicated
163 in the ``who'' service specification; see
165 The messages sent and received, are of the form:
166 .Bd -literal -offset indent
168 char out_line[8]; /* tty name */
169 char out_name[8]; /* user id */
170 long out_time; /* time on */
179 char wd_hostname[32];
183 struct outmp we_utmp;
185 } wd_we[1024 / sizeof (struct whoent)];
189 All fields are converted to network byte order prior to
190 transmission. The load averages are as calculated by the
192 program, and represent load averages over the 5, 10, and 15 minute
193 intervals prior to a server's transmission; they are multiplied by 100
194 for representation in an integer. The host name
195 included is that returned by the
197 system call, with any trailing domain name omitted.
198 The array at the end of the message contains information about
199 the users logged in to the sending machine. This information
200 includes the contents of the
202 entry for each non-idle terminal line and a value indicating the
203 time in seconds since a character was last received on the terminal line.
205 Messages received by the
207 server are discarded unless they originated at an
211 option was specified. In addition, if the host's name, as specified
212 in the message, contains any unprintable
215 message is discarded. Valid messages received by
217 are placed in files named
221 These files contain only the most recent message, in the
222 format described above.
224 Status messages are generated by default approximately once every
231 every 30 minutes to guard against
232 the possibility that this file is not the system
233 image currently operating.
243 Status information should be sent only upon request rather than continuously.
244 People often interpret the server dying
245 or network communication failures
246 as a machine going down.