1 .\" Copyright (c) 1980, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. Neither the name of the University nor the names of its contributors
13 .\" may be used to endorse or promote products derived from this software
14 .\" without specific prior written permission.
16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" @(#)timed.8 8.1 (Berkeley) 6/6/93
29 .\" $FreeBSD: src/usr.sbin/timed/timed/timed.8,v 1.7.2.6 2003/03/11 22:31:34 trhodes Exp $
30 .\" $DragonFly: src/usr.sbin/timed/timed/timed.8,v 1.3 2007/12/16 02:55:38 thomas Exp $
37 .Nd time server daemon
47 utility is a time server daemon,
48 it is invoked at boot time by setting the
52 It synchronizes the host's time with the time of other
53 machines, which are also running
55 in a local area network.
56 These time servers will slow down the clocks of some machines
57 and speed up the clocks of others to bring them to the average network time.
58 The average network time is computed from measurements of clock differences
61 timestamp request message.
63 The following options are available:
64 .Bl -tag -width indent
66 Enable debugging mode;
67 do not detach from the terminal.
71 to the list of networks to ignore.
73 to which the machine is directly connected
76 This option may be specified multiple times
77 to add more than one network to the list.
79 Create a list of trusted hosts.
82 utility will only accept trusted hosts as masters.
83 If it finds an untrusted host claiming to be master,
85 will suppress incoming messages from that host
86 and call for a new election.
87 This option implies the
90 If this option is not specified,
91 all hosts on the connected networks are treated as trustworthy.
93 Allow this host to become a
99 to the list of allowed networks.
101 to which the machine is directly connected
104 This option may be specified multiple times
105 to add more than one network to the list.
107 Enable tracing of received messages
109 .It Pa /var/log/timed.log .
110 Tracing can be turned on or off while
121 are mutually exclusive
122 and require as arguments real networks to which
123 the host is connected
126 If neither flag is specified,
128 will listen on all connected networks.
136 flags will always remain a slave.
141 will treat all machines as trustworthy.
145 utility is based on a master-slave
149 is started on a machine, it asks the master for the network time
150 and sets the host's clock to that time.
151 After that, it accepts synchronization messages periodically sent by
154 to perform the needed corrections on the host's clock.
156 It also communicates with
158 in order to set the date globally,
164 If the machine running the master becomes unreachable,
165 the slaves will elect a new master
166 from among those slaves
167 which are running with at least one of the
175 normally checks for a master time server on each network to which
176 it is connected, except as modified by the
180 options described above.
181 It will request synchronization service from the first master server
187 flags, it will provide synchronization service on any attached networks
188 on which no trusted master server was detected.
189 Such a server propagates the time computed by the top-level master.
192 utility will periodically check for the presence of a master
193 on those networks for which it is operating as a slave.
194 If it finds that there are no trusted masters on a network,
195 it will begin the election process on that network.
197 One way to synchronize a group of machines is to use an
200 synchronize the clock of one machine to a distant standard or a radio
203 to tell its timed daemon to trust only itself.
205 Messages printed by the kernel on the system console occur with
207 This means that the clock stops while they are printing.
208 A machine with many disk or network hardware problems and consequent
209 messages cannot keep good time by itself. Each message typically causes
210 the clock to lose a dozen milliseconds. A time daemon can
213 Messages in the system log about machines that failed to respond
214 usually indicate machines that crashed or were turned off.
215 Complaints about machines that failed to respond to initial time
216 settings are often associated with "multi-homed" machines
217 that looked for time masters on more than one network and eventually
218 chose to become a slave on the other network.
220 Temporal chaos will result if two or more time daemons attempt
221 to adjust the same clock.
224 and another time daemon are run on the same machine,
227 flag is used, so that
229 never attempts to adjust the local clock.
231 The protocol is based on
233 broadcasts. All machines within
234 the range of a broadcast that are using the
236 protocol must cooperate.
237 There cannot be more than a single administrative domain using the
239 flag among all machines reached by a broadcast packet.
240 Failure to follow this rule is usually indicated by complaints concerning
241 "untrusted" machines in the system log.
243 .Bl -tag -width /var/log/timed.masterlog -compact
244 .It Pa /var/log/timed.log
245 tracing file for timed
246 .It Pa /var/log/timed.masterlog
247 log file for master timed
258 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"