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7 .TH IN.RWHOD 1M "Dec 8, 2001"
8 .SH NAME
9 in.rwhod, rwhod \- system status server
10 .SH SYNOPSIS
11 .LP
12 .nf
13 \fB/usr/sbin/in.rwhod\fR [\fB-m\fR [\fIttl\fR]]
14 .fi
15
16 .SH DESCRIPTION
17 .sp
18 .LP
19 \fBin.rwhod\fR is the server which maintains the database used by the
20 \fBrwho\fR(1) and \fBruptime\fR(1) programs. Its operation is predicated on
21 the ability to broadcast or multicast messages on a network.
22 .sp
23 .LP
24 \fBin.rwhod\fR operates as both a producer and consumer of status information.
25 As a producer of information it periodically queries the state of the system
26 and constructs status messages which are broadcast or multicast on a network.
27 As a consumer of information, it listens for other \fBin.rwhod\fR servers'
28 status messages, validating them, then recording them in a collection of files
29 located in the directory \fB/var/spool/rwho\fR.
30 .sp
31 .LP
32 The \fBrwho\fR server transmits and receives messages at the port indicated in
33 the \fBrwho\fR service specification, see \fBservices\fR(4). The messages sent
34 and received are defined in \fB/usr/include/protocols/rwhod.h\fR and are of the
35 form:
36 .sp
37 .in +2
38 .nf
39 struct outmp {
40 char out_line[8]; /* tty name */
41 char out_name[8]; /* user id */
42 long out_time; /* time on */
43 };
44 struct whod {
45 char wd_vers;
46 char wd_type;
47 char wd_fill[2];
48 int wd_sendtime;
49 int wd_recvtime;
50 char wd_hostname[32];
51 int wd_loadav[3];
52 int wd_boottime;
53 struct whoent {
54 struct outmp we_utmp;
55 int we_idle;
56 } wd_we[1024 / sizeof (struct whoent)];
57 };
58 .fi
59 .in -2
60 .sp
61
62 .sp
63 .LP
64 All fields are converted to network byte order prior to transmission. The load
65 averages are as calculated by the \fBw\fR(1) program, and represent load
66 averages over the 1, 5, and 15 minute intervals prior to a server's
67 transmission. The host name included is that returned by the \fBuname\fR(2)
68 system call. The array at the end of the message contains information about the
69 users who are logged in to the sending machine. This information includes the
70 contents of the \fButmpx\fR(4) entry for each non-idle terminal line and a
71 value indicating the time since a character was last received on the terminal
72 line.
73 .sp
74 .LP
75 Messages received by the \fBrwho\fR server are discarded unless they originated
76 at a \fBrwho\fR server's port. In addition, if the host's name, as specified
77 in the message, contains any unprintable \fBASCII\fR characters, the message is
78 discarded. Valid messages received by \fBin.rwhod\fR are placed in files named
79 \fBwhod.\fR\fBhostname\fR in the directory \fB/var/spool/rwho\fR. These files
80 contain only the most recent message, in the format described above.
81 .sp
82 .LP
83 Status messages are generated approximately once every 3 minutes.
84 .SH OPTIONS
85 .sp
86 .LP
87 The following options are supported:
88 .sp
89 .ne 2
90 .na
91 \fB\fB\fR\fB-m\fR\fB \fR[\fI ttl \fR]\fR
92 .ad
93 .RS 14n
94 Use the rwho \fBIP\fR multicast address (224.0.1.3) when transmitting. Receive
95 announcements both on this multicast address and on the \fBIP\fR broadcast
96 address. If \fIttl\fR is not specified \fBin.rwhod\fR multicasts on all
97 interfaces but with the \fBIP\fR TimeToLive set to 1 (that is, packets are not
98 forwarded by multicast routers.) If \fIttl\fR is specified \fBin.rwhod\fR
99 only transmits packets on one interface and setting the \fBIP\fR TimeToLive to
100 the specified \fIttl\fR.
101 .RE
102
103 .SH FILES
104 .sp
105 .ne 2
106 .na
107 \fB\fB/var/spool/rwho/whod.*\fR\fR
108 .ad
109 .RS 26n
110 information about other machines
111 .RE
112
113 .SH SEE ALSO
114 .sp
115 .LP
116 \fBruptime\fR(1), \fBrwho\fR(1), \fBw\fR(1), \fBuname\fR(2), \fBservices\fR(4),
117 \fButmpx\fR(4), \fBattributes\fR(5)
118 .SH WARNINGS
119 .sp
120 .LP
121 This service can cause network performance problems when used by several hosts
122 on the network. It is not run at most sites by default. If used, include the
123 \fB-m\fR multicast option.
124 .SH NOTES
125 .sp
126 .LP
127 This service takes up progressively more network bandwidth as the number of
128 hosts on the local net increases. For large networks, the cost becomes
129 prohibitive.
130 .sp
131 .LP
132 \fBin.rwhod\fR should relay status information between networks. People often
133 interpret the server dying as a machine going down.