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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 1.2 2003/06/17 04:30:03 dillon Exp $
41 .Nd time server daemon
51 utility is a time server daemon
52 which is normally invoked at boot time from the
55 It synchronizes the host's time with the time of other
56 machines, which are also running
58 in a local area network.
59 These time servers will slow down the clocks of some machines
60 and speed up the clocks of others to bring them to the average network time.
61 The average network time is computed from measurements of clock differences
64 timestamp request message.
66 The following options are available:
67 .Bl -tag -width indent
69 Enable debugging mode;
70 do not detach from the terminal.
74 to the list of networks to ignore.
76 to which the machine is directly connected
79 This option may be specified multiple times
80 to add more than one network to the list.
82 Create a list of trusted hosts.
85 utility will only accept trusted hosts as masters.
86 If it finds an untrusted host claiming to be master,
88 will suppress incoming messages from that host
89 and call for a new election.
90 This option implies the
93 If this option is not specified,
94 all hosts on the connected networks are treated as trustworthy.
96 Allow this host to become a
102 to the list of allowed networks.
104 to which the machine is directly connected
107 This option may be specified multiple times
108 to add more than one network to the list.
110 Enable tracing of received messages
112 .It Pa /var/log/timed.log .
113 Tracing can be turned on or off while
124 are mutually exclusive
125 and require as arguments real networks to which
126 the host is connected
129 If neither flag is specified,
131 will listen on all connected networks.
139 flags will always remain a slave.
144 will treat all machines as trustworthy.
148 utility is based on a master-slave
152 is started on a machine, it asks the master for the network time
153 and sets the host's clock to that time.
154 After that, it accepts synchronization messages periodically sent by
157 to perform the needed corrections on the host's clock.
159 It also communicates with
161 in order to set the date globally,
167 If the machine running the master becomes unreachable,
168 the slaves will elect a new master
169 from among those slaves
170 which are running with at least one of the
178 normally checks for a master time server on each network to which
179 it is connected, except as modified by the
183 options described above.
184 It will request synchronization service from the first master server
190 flags, it will provide synchronization service on any attached networks
191 on which no trusted master server was detected.
192 Such a server propagates the time computed by the top-level master.
195 utility will periodically check for the presence of a master
196 on those networks for which it is operating as a slave.
197 If it finds that there are no trusted masters on a network,
198 it will begin the election process on that network.
200 One way to synchronize a group of machines is to use an
203 synchronize the clock of one machine to a distant standard or a radio
206 to tell its timed daemon to trust only itself.
208 Messages printed by the kernel on the system console occur with
210 This means that the clock stops while they are printing.
211 A machine with many disk or network hardware problems and consequent
212 messages cannot keep good time by itself. Each message typically causes
213 the clock to lose a dozen milliseconds. A time daemon can
216 Messages in the system log about machines that failed to respond
217 usually indicate machines that crashed or were turned off.
218 Complaints about machines that failed to respond to initial time
219 settings are often associated with "multi-homed" machines
220 that looked for time masters on more than one network and eventually
221 chose to become a slave on the other network.
223 Temporal chaos will result if two or more time daemons attempt
224 to adjust the same clock.
227 and another time daemon are run on the same machine,
230 flag is used, so that
232 never attempts to adjust the local clock.
234 The protocol is based on
236 broadcasts. All machines within
237 the range of a broadcast that are using the
239 protocol must cooperate.
240 There cannot be more than a single administrative domain using the
242 flag among all machines reached by a broadcast packet.
243 Failure to follow this rule is usually indicated by complaints concerning
244 "untrusted" machines in the system log.
246 .Bl -tag -width /var/log/timed.masterlog -compact
247 .It Pa /var/log/timed.log
248 tracing file for timed
249 .It Pa /var/log/timed.masterlog
250 log file for master timed
260 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"