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32 .\" @(#)rwhod.8 8.2 (Berkeley) 12/11/93
39 .Nd system status server
47 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.
58 operates as both a producer and consumer of status information,
61 (listen mode) option is specified, in which case
62 it acts as a consumer only.
63 As a producer of information it periodically
64 queries the state of the system and constructs
65 status messages which are broadcasted or multicasted on a network.
66 As a consumer of information, it listens for other
68 servers' status messages, validating them, then recording
69 them in a collection of files located in the directory
74 option enables insecure mode, which causes
76 to ignore the source port on incoming packets.
80 option enables listen mode, which causes
82 to not broadcast any information.
83 This allows you to monitor other machines'
85 information, without broadcasting your own.
91 to use IP multicast (instead of
92 broadcast) on all interfaces that have
93 the IFF_MULTICAST flag set in their "ifnet" structs
94 (excluding the loopback interface). The multicast
95 reports are sent with a time-to-live of 1, to prevent
96 forwarding beyond the directly-connected subnet(s).
100 argument is supplied with the
104 will send IP multicast datagrams with a
107 via a SINGLE interface rather
110 must be between 0 and
111 32 (or MAX_MULTICAST_SCOPE). Note that
117 specifies transmission on one interface only.
123 argument, the program accepts multicast
125 reports from all multicast-capable interfaces. If a
127 argument is given, it accepts multicast reports from only one interface, the
128 one on which reports are sent (which may be controlled via the host's routing
129 table). Regardless of the
131 option, the program accepts broadcast or
132 unicast reports from all interfaces. Thus, this program will hear the
133 reports of old, non-multicasting
135 but, if multicasting is used,
138 won't hear the reports generated by this program.
140 The server transmits and receives messages at the port indicated
141 in the ``who'' service specification; see
143 The messages sent and received, are of the form:
144 .Bd -literal -offset indent
146 char out_line[8]; /* tty name */
147 char out_name[8]; /* user id */
148 long out_time; /* time on */
157 char wd_hostname[32];
161 struct outmp we_utmp;
163 } wd_we[1024 / sizeof (struct whoent)];
167 All fields are converted to network byte order prior to
168 transmission. The load averages are as calculated by the
170 program, and represent load averages over the 5, 10, and 15 minute
171 intervals prior to a server's transmission; they are multiplied by 100
172 for representation in an integer. The host name
173 included is that returned by the
175 system call, with any trailing domain name omitted.
176 The array at the end of the message contains information about
177 the users logged in to the sending machine. This information
178 includes the contents of the
180 entry for each non-idle terminal line and a value indicating the
181 time in seconds since a character was last received on the terminal line.
183 Messages received by the
185 server are discarded unless they originated at an
189 option was specified. In addition, if the host's name, as specified
190 in the message, contains any unprintable
193 message is discarded. Valid messages received by
195 are placed in files named
199 These files contain only the most recent message, in the
200 format described above.
202 Status messages are generated approximately once every
209 every 30 minutes to guard against
210 the possibility that this file is not the system
211 image currently operating.
216 Status information should be sent only upon request rather than continuously.
217 People often interpret the server dying
218 or network communication failures
219 as a machine going down.