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28 .\" @(#)timed.8 8.1 (Berkeley) 6/6/93
36 .Nd time server daemon
40 .Op Fl i Ar network | Fl n Ar network
45 utility is a time server daemon
46 which is normally invoked at boot time from the
49 It synchronizes the host's time with the time of other
50 machines, which are also running
52 in a local area network.
53 These time servers will slow down the clocks of some machines
54 and speed up the clocks of others to bring them to the average network time.
55 The average network time is computed from measurements of clock differences
58 timestamp request message.
60 The following options are available:
61 .Bl -tag -width indent
63 Enable debugging mode;
64 do not detach from the terminal.
68 to the list of networks to ignore.
70 to which the machine is directly connected
73 This option may be specified multiple times
74 to add more than one network to the list.
78 Create a list of trusted hosts.
80 Can take one or more parameters.
83 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.
89 Use real host names (resolvable by RDNS) not aliases (eg in
91 parlance: use A names, not C names).
93 Use full names eg time1.domain.com not time1.
96 automatically includes the functionality of
100 does not need to asserted).
105 all hosts on connected networks are treated as trustworthy.
108 Allow this host to become a
114 to the list of allowed networks.
116 to which the machine is directly connected
119 This option may be specified multiple times
120 to add more than one network to the list.
122 Enable tracing of received messages
124 .Pa /var/log/timed.log .
125 Tracing can be turned on or off while
136 flags are mutually exclusive
137 and require as arguments real networks to which
138 the host is connected
141 If neither flag is specified,
143 will listen on all connected networks.
151 flags will always remain a slave.
156 will treat all machines as trustworthy.
160 utility is based on a master-slave
164 is started on a machine, it asks the master for the network time
165 and sets the host's clock to that time.
166 After that, it accepts synchronization messages periodically sent by
169 to perform the needed corrections on the host's clock.
171 It also communicates with
173 in order to set the date globally,
179 If the machine running the master becomes unreachable,
180 the slaves will elect a new master
181 from among those slaves
182 which are running with at least one of the
190 normally checks for a master time server on each network to which
191 it is connected, except as modified by the
195 options described above.
196 It will request synchronization service from the first master server
202 flags, it will provide synchronization service on any attached networks
203 on which no trusted master server was detected.
204 Such a server propagates the time computed by the top-level master.
207 utility will periodically check for the presence of a master
208 on those networks for which it is operating as a slave.
209 If it finds that there are no trusted masters on a network,
210 it will begin the election process on that network.
212 One way to synchronize a group of machines is to use
215 synchronize the clock of one machine to a distant standard or a radio
220 to trust only itself.
222 Messages printed by the kernel on the system console occur with
224 This means that the clock stops while they are printing.
225 A machine with many disk or network hardware problems and consequent
226 messages cannot keep good time by itself.
227 Each message typically causes
228 the clock to lose a dozen milliseconds.
229 A time daemon can correct the result.
231 Messages in the system log about machines that failed to respond
232 usually indicate machines that crashed or were turned off.
233 Complaints about machines that failed to respond to initial time
234 settings are often associated with
236 machines that looked for time masters on more than one network and eventually
237 chose to become a slave on the other network.
239 Temporal chaos will result if two or more time daemons attempt
240 to adjust the same clock.
243 and another time daemon are run on the same machine,
246 flag is used, so that
248 never attempts to adjust the local clock.
250 The protocol is based on
253 All machines within the range of a broadcast that are using the
255 protocol must cooperate.
256 There cannot be more than a single administrative domain using the
258 flag among all machines reached by a broadcast packet.
259 Failure to follow this rule is usually indicated by complaints concerning
261 machines in the system log.
263 .Bl -tag -width /var/log/timed.masterlog -compact
264 .It Pa /var/log/timed.log
267 .It Pa /var/log/timed.masterlog
280 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"