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32 .\" @(#)timed.8 8.1 (Berkeley) 6/6/93
40 .Nd time server daemon
44 .Op Fl i Ar network | Fl n Ar network
49 utility is a time server daemon
50 which is normally invoked at boot time from the
53 It synchronizes the host's time with the time of other
54 machines, which are also running
56 in a local area network.
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 following options are available:
65 .Bl -tag -width indent
67 Enable debugging mode;
68 do not detach from the terminal.
72 to the list of networks to ignore.
74 to which the machine is directly connected
77 This option may be specified multiple times
78 to add more than one network to the list.
80 Create a list of trusted hosts.
83 utility will only accept trusted hosts as masters.
84 If it finds an untrusted host claiming to be master,
86 will suppress incoming messages from that host
87 and call for a new election.
88 This option implies the
91 If this option is not specified,
92 all hosts on the connected networks are treated as trustworthy.
94 Allow this host to become a
100 to the list of allowed networks.
102 to which the machine is directly connected
105 This option may be specified multiple times
106 to add more than one network to the list.
108 Enable tracing of received messages
110 .Pa /var/log/timed.log .
111 Tracing can be turned on or off while
122 flags are mutually exclusive
123 and require as arguments real networks to which
124 the host is connected
127 If neither flag is specified,
129 will listen on all connected networks.
137 flags will always remain a slave.
142 will treat all machines as trustworthy.
146 utility is based on a master-slave
150 is started on a machine, it asks the master for the network time
151 and sets the host's clock to that time.
152 After that, it accepts synchronization messages periodically sent by
155 to perform the needed corrections on the host's clock.
157 It also communicates with
159 in order to set the date globally,
165 If the machine running the master becomes unreachable,
166 the slaves will elect a new master
167 from among those slaves
168 which are running with at least one of the
176 normally checks for a master time server on each network to which
177 it is connected, except as modified by the
181 options described above.
182 It will request synchronization service from the first master server
188 flags, it will provide synchronization service on any attached networks
189 on which no trusted master server was detected.
190 Such a server propagates the time computed by the top-level master.
193 utility will periodically check for the presence of a master
194 on those networks for which it is operating as a slave.
195 If it finds that there are no trusted masters on a network,
196 it will begin the election process on that network.
198 One way to synchronize a group of machines is to use
201 synchronize the clock of one machine to a distant standard or a radio
206 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.
213 Each message typically causes
214 the clock to lose a dozen milliseconds.
215 A time daemon can correct the result.
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
222 machines that looked for time masters on more than one network and eventually
223 chose to become a slave on the other network.
225 Temporal chaos will result if two or more time daemons attempt
226 to adjust the same clock.
229 and another time daemon are run on the same machine,
232 flag is used, so that
234 never attempts to adjust the local clock.
236 The protocol is based on
239 All machines within the range of a broadcast that are using the
241 protocol must cooperate.
242 There cannot be more than a single administrative domain using the
244 flag among all machines reached by a broadcast packet.
245 Failure to follow this rule is usually indicated by complaints concerning
247 machines in the system log.
249 .Bl -tag -width /var/log/timed.masterlog -compact
250 .It Pa /var/log/timed.log
253 .It Pa /var/log/timed.masterlog
266 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"