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32 .\" @(#)timed.8 6.7 (Berkeley) 5/11/93
36 .Os "Linux NetKit (0.17)"
39 .Nd time server daemon
47 .Op Fl F Ar host1 host2 ...
50 is a time server daemon and is normally invoked
54 It synchronizes the host's time with the time of other
55 machines in a local area network running
57 These time servers will slow down the clocks of some machines
58 and speed up the clocks of others to bring them to the average network time.
59 The average network time is computed from measurements of clock differences
62 timestamp request message.
64 The service provided by
66 is based on a master-slave
70 is started on a machine, it asks the master for the network time
71 and sets the host's clock to that time.
72 After that, it accepts synchronization messages periodically sent by
75 to perform the needed corrections on the host's clock.
77 It also communicates with
79 in order to set the date globally,
82 a timed control program.
83 If the machine running the master crashes, then the slaves will elect
84 a new master from among slaves running with the
93 flags will remain a slave.
98 to trace the messages it receives in the
100 .Pa /var/log/timed.log .
101 Tracing can be turned on or off by the program
105 flag is for debugging the daemon.
106 It causes the program to not put itself into the background.
109 checks for a master time server on each network to which
110 it is connected, except as modified by the options described below.
111 It will request synchronization service from the first master server
115 flag, it will provide synchronization service on any attached networks
116 on which no current master server was detected.
117 Such a server propagates the time computed by the top-level master.
120 flag, followed by the name of a network which the host is connected to
123 overrides the default choice of the
124 network addresses made by the program.
127 flag appears, that network name is added to a list of valid networks.
128 All other networks are ignored.
131 flag, followed by the name of a network to which the host is connected
134 overrides the default choice of the network addresses made by the program.
137 flag appears, that network name is added to a list of networks to ignore.
138 All other networks are used by the time daemon.
143 flags are meaningless if used together.
146 checks for a master time server on each network to which
147 it is connected, except as modified by the
151 options described above.
152 If it finds masters on more than one network, it chooses one network
153 on which to be a "slave," and then periodically checks the other
154 networks to see if the masters there have disappeared.
156 One way to synchronize a group of machines is to use an NTP daemon to
157 synchronize the clock of one machine to a distant standard or a radio
160 to tell its timed daemon to trust only itself.
162 Messages printed by the kernel on the system console occur with
164 This means that the clock stops while they are printing.
165 A machine with many disk or network hardware problems and consequent
166 messages cannot keep good time by itself. Each message typically causes
167 the clock to lose a dozen milliseconds. A time daemon can
170 Messages in the system log about machines that failed to respond
171 usually indicate machines that crashed or were turned off.
172 Complaints about machines that failed to respond to initial time
173 settings are often associated with
175 machines that looked for time masters on more than one network and eventually
176 chose to become slaves on other networks.
178 If two or more time daemons, whether
182 try to adjust the same clock, temporal chaos will result.
185 and another time daemon are run on the same machine,
188 flag is used, so that
190 never attempts to adjust the local clock.
192 The protocol is based on UDP/IP broadcasts. All machines within
193 the range of a broadcast that are using the TSP protocol must cooperate.
194 There cannot be more than a single administrative domain using the
196 flag among all machines reached by a broadcast packet.
197 Failure to follow this rule is usually indicated by complaints concerning
199 machines in the system log.
201 .Bl -tag -width /var/log/timed.masterlog -compact
202 .It Pa /var/log/timed.log
203 tracing file for timed
204 .It Pa /var/log/timed.masterlog
205 log file for master timed
214 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"