xref: /dragonfly/usr.sbin/rwhod/rwhod.8 (revision 6e285212) 
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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 $
34.\" $DragonFly: src/usr.sbin/rwhod/rwhod.8,v 1.2 2003/06/17 04:30:03 dillon Exp $
35.\"
36.Dd December 11, 1993
37.Dt RWHOD 8
38.Os
39.Sh NAME
40.Nm rwhod
41.Nd system status server
42.Sh SYNOPSIS
43.Nm
44.Op Fl i
45.Op Fl p
46.Op Fl l
47.Op Fl m Op Ar ttl
48.Sh DESCRIPTION
49The
50.Nm
51utility is the server which maintains the database used by the
52.Xr rwho 1
53and
54.Xr ruptime 1
55programs.  Its operation is predicated on the ability to
56.Em broadcast
57or
58.Em multicast
59messages on a network.
60.Pp
61The
62.Nm
63utility operates as both a producer and consumer of status information,
64unless the
65.Fl l
66(listen mode) option is specified, in which case
67it acts as a consumer only.
68As a producer of information it periodically
69queries the state of the system and constructs
70status messages which are broadcasted or multicasted on a network.
71As a consumer of information, it listens for other
72.Nm
73servers' status messages, validating them, then recording
74them in a collection of files located in the directory
75.Pa /var/rwho .
76.Pp
77The
78.Fl i
79option enables insecure mode, which causes
80.Nm
81to ignore the source port on incoming packets.
82.Pp
83The
84.Fl p
85option tells
86.Nm
87to ignore all
88.Dv POINTOPOINT
89interfaces.  This is useful if you do not wish to keep dial on demand
90interfaces permanently active.
91.Pp
92The
93.Fl l
94option enables listen mode, which causes
95.Nm
96to not broadcast any information.
97This allows you to monitor other machines'
98.Nm
99information, without broadcasting your own.
100.Pp
101The
102.Fl m
103option causes
104.Nm
105to use IP multicast (instead of
106broadcast) on all interfaces that have
107the IFF_MULTICAST flag set in their "ifnet" structs
108(excluding the loopback interface).  The multicast
109reports are sent with a time-to-live of 1, to prevent
110forwarding beyond the directly-connected subnet(s).
111.Pp
112If the optional
113.Ar ttl
114argument is supplied with the
115.Fl m
116flag,
117.Nm
118will send IP multicast datagrams with a
119time-to-live of
120.Ar ttl ,
121via a SINGLE interface rather
122than all interfaces.
123.Ar ttl
124must be between 0 and
12532 (or MAX_MULTICAST_SCOPE).  Note that
126.Fl m Ar 1
127is different from
128.Fl m ,
129in that
130.Fl m Ar 1
131specifies transmission on one interface only.
132.Pp
133When
134.Fl m
135is used without a
136.Ar ttl
137argument, the program accepts multicast
138.Nm
139reports from all multicast-capable interfaces.  If a
140.Ar ttl
141argument is given, it accepts multicast reports from only one interface, the
142one on which reports are sent (which may be controlled via the host's routing
143table).  Regardless of the
144.Fl m
145option, the program accepts broadcast or
146unicast reports from all interfaces.  Thus, this program will hear the
147reports of old, non-multicasting
148.Nm Ns s ,
149but, if multicasting is used,
150those old
151.Nm Ns s
152won't hear the reports generated by this program.
153.Pp
154The server transmits and receives messages at the port indicated
155in the ``who'' service specification; see
156.Xr services 5 .
157The messages sent and received, are of the form:
158.Bd -literal -offset indent
159struct	outmp {
160	char	out_line[8];		/* tty name */
161	char	out_name[8];		/* user id */
162	long	out_time;		/* time on */
163};
164
165struct	whod {
166	char	wd_vers;
167	char	wd_type;
168	char	wd_fill[2];
169	int	wd_sendtime;
170	int	wd_recvtime;
171	char	wd_hostname[32];
172	int	wd_loadav[3];
173	int	wd_boottime;
174	struct	whoent {
175		struct	outmp we_utmp;
176		int	we_idle;
177	} wd_we[1024 / sizeof (struct whoent)];
178};
179.Ed
180.Pp
181All fields are converted to network byte order prior to
182transmission.  The load averages are as calculated by the
183.Xr w 1
184program, and represent load averages over the 5, 10, and 15 minute
185intervals prior to a server's transmission; they are multiplied by 100
186for representation in an integer.  The host name
187included is that returned by the
188.Xr gethostname 3
189system call, with any trailing domain name omitted.
190The array at the end of the message contains information about
191the users logged in to the sending machine.  This information
192includes the contents of the
193.Xr utmp 5
194entry for each non-idle terminal line and a value indicating the
195time in seconds since a character was last received on the terminal line.
196.Pp
197Messages received by the
198.Nm rwho
199server are discarded unless they originated at an
200.Nm rwho
201server's port or the
202.Fl i
203option was specified.  In addition, if the host's name, as specified
204in the message, contains any unprintable
205.Tn ASCII
206characters, the
207message is discarded.  Valid messages received by
208.Nm
209are placed in files named
210.Pa whod.hostname
211in the directory
212.Pa /var/rwho .
213These files contain only the most recent message, in the
214format described above.
215.Pp
216Status messages are generated approximately once every
2173 minutes.
218.Nm Rwhod
219performs an
220.Xr nlist 3
221on
222.Pa /kernel
223every 30 minutes to guard against
224the possibility that this file is not the system
225image currently operating.
226.Sh SEE ALSO
227.Xr ruptime 1 ,
228.Xr rwho 1
229.Sh BUGS
230Status information should be sent only upon request rather than continuously.
231People often interpret the server dying
232or network communication failures
233as a machine going down.
234.Sh HISTORY
235The
236.Nm
237utility appeared in
238.Bx 4.2 .
239