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32 .\" @(#)timed.8 8.1 (Berkeley) 6/6/93
33 .\" $FreeBSD: src/usr.sbin/timed/timed/timed.8,v 1.7.2.6 2003/03/11 22:31:34 trhodes Exp $
34 .\" $DragonFly: src/usr.sbin/timed/timed/timed.8,v 1.3 2007/12/16 02:55:38 thomas Exp $
41 .Nd time server daemon
51 utility is a time server daemon,
52 it is invoked at boot time by setting the
56 It synchronizes the host's time with the time of other
57 machines, which are also running
59 in a local area network.
60 These time servers will slow down the clocks of some machines
61 and speed up the clocks of others to bring them to the average network time.
62 The average network time is computed from measurements of clock differences
65 timestamp request message.
67 The following options are available:
68 .Bl -tag -width indent
70 Enable debugging mode;
71 do not detach from the terminal.
75 to the list of networks to ignore.
77 to which the machine is directly connected
80 This option may be specified multiple times
81 to add more than one network to the list.
83 Create a list of trusted hosts.
86 utility will only accept trusted hosts as masters.
87 If it finds an untrusted host claiming to be master,
89 will suppress incoming messages from that host
90 and call for a new election.
91 This option implies the
94 If this option is not specified,
95 all hosts on the connected networks are treated as trustworthy.
97 Allow this host to become a
103 to the list of allowed networks.
105 to which the machine is directly connected
108 This option may be specified multiple times
109 to add more than one network to the list.
111 Enable tracing of received messages
113 .It Pa /var/log/timed.log .
114 Tracing can be turned on or off while
125 are mutually exclusive
126 and require as arguments real networks to which
127 the host is connected
130 If neither flag is specified,
132 will listen on all connected networks.
140 flags will always remain a slave.
145 will treat all machines as trustworthy.
149 utility is based on a master-slave
153 is started on a machine, it asks the master for the network time
154 and sets the host's clock to that time.
155 After that, it accepts synchronization messages periodically sent by
158 to perform the needed corrections on the host's clock.
160 It also communicates with
162 in order to set the date globally,
168 If the machine running the master becomes unreachable,
169 the slaves will elect a new master
170 from among those slaves
171 which are running with at least one of the
179 normally checks for a master time server on each network to which
180 it is connected, except as modified by the
184 options described above.
185 It will request synchronization service from the first master server
191 flags, it will provide synchronization service on any attached networks
192 on which no trusted master server was detected.
193 Such a server propagates the time computed by the top-level master.
196 utility will periodically check for the presence of a master
197 on those networks for which it is operating as a slave.
198 If it finds that there are no trusted masters on a network,
199 it will begin the election process on that network.
201 One way to synchronize a group of machines is to use an
204 synchronize the clock of one machine to a distant standard or a radio
207 to tell its timed daemon to trust only itself.
209 Messages printed by the kernel on the system console occur with
211 This means that the clock stops while they are printing.
212 A machine with many disk or network hardware problems and consequent
213 messages cannot keep good time by itself. Each message typically causes
214 the clock to lose a dozen milliseconds. A time daemon can
217 Messages in the system log about machines that failed to respond
218 usually indicate machines that crashed or were turned off.
219 Complaints about machines that failed to respond to initial time
220 settings are often associated with "multi-homed" machines
221 that looked for time masters on more than one network and eventually
222 chose to become a slave on the other network.
224 Temporal chaos will result if two or more time daemons attempt
225 to adjust the same clock.
228 and another time daemon are run on the same machine,
231 flag is used, so that
233 never attempts to adjust the local clock.
235 The protocol is based on
237 broadcasts. All machines within
238 the range of a broadcast that are using the
240 protocol must cooperate.
241 There cannot be more than a single administrative domain using the
243 flag among all machines reached by a broadcast packet.
244 Failure to follow this rule is usually indicated by complaints concerning
245 "untrusted" machines in the system log.
247 .Bl -tag -width /var/log/timed.masterlog -compact
248 .It Pa /var/log/timed.log
249 tracing file for timed
250 .It Pa /var/log/timed.masterlog
251 log file for master timed
262 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"