1.\" Copyright (c) 1980, 1991 Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)timed.8 6.7 (Berkeley) 05/11/93 7.\" 8.Dd 9.Dt TIMED 8 10.Os BSD 4.3 11.Sh NAME 12.Nm timed 13.Nd time server daemon 14.Sh SYNOPSIS 15.Nm timed 16.Op Fl M 17.Op Fl t 18.Op Fl d 19.Op Fl i Ar network 20.Op Fl n Ar network 21.Op Fl F Ar host1 host2 ... 22.Sh DESCRIPTION 23This 24is a time server daemon and is normally invoked 25at boot time from the 26.Xr rc 8 27file. 28It synchronizes the host's time with the time of other 29machines in a local area network running 30.Nm timed 8 . 31These time servers will slow down the clocks of some machines 32and speed up the clocks of others to bring them to the average network time. 33The average network time is computed from measurements of clock differences 34using the 35.Tn ICMP 36timestamp request message. 37.Pp 38The service provided by 39.Nm timed 40is based on a master-slave 41scheme. 42When 43.Nm timed 8 44is started on a machine, it asks the master for the network time 45and sets the host's clock to that time. 46After that, it accepts synchronization messages periodically sent by 47the master and calls 48.Xr adjtime 2 49to perform the needed corrections on the host's clock. 50.Pp 51It also communicates with 52.Xr date 1 53in order to set the date globally, 54and with 55.Xr timedc 8 , 56a timed control program. 57If the machine running the master crashes, then the slaves will elect 58a new master from among slaves running with the 59.Fl M 60flag. 61A 62.Nm timed 63running without the 64.Fl M 65or 66.Fl F 67flags will remain a slave. 68The 69.Fl t 70flag enables 71.Nm timed 72to trace the messages it receives in the 73file 74.Pa /var/log/timed.log . 75Tracing can be turned on or off by the program 76.Xr timedc 8 . 77The 78.Fl d 79flag is for debugging the daemon. 80It causes the program to not put itself into the background. 81Normally 82.Nm timed 83checks for a master time server on each network to which 84it is connected, except as modified by the options described below. 85It will request synchronization service from the first master server 86located. 87If permitted by the 88.Fl M 89flag, it will provide synchronization service on any attached networks 90on which no current master server was detected. 91Such a server propagates the time computed by the top-level master. 92The 93.Fl n 94flag, followed by the name of a network which the host is connected to 95(see 96.Xr networks 5 ) , 97overrides the default choice of the 98network addresses made by the program. 99Each time the 100.Fl n 101flag appears, that network name is added to a list of valid networks. 102All other networks are ignored. 103The 104.Fl i 105flag, followed by the name of a network to which the host is connected 106(see 107.Xr networks 5 ) , 108overrides the default choice of the network addresses made by the program. 109Each time the 110.Fl i 111flag appears, that network name is added to a list of networks to ignore. 112All other networks are used by the time daemon. 113The 114.Fl n 115and 116.Fl i 117flags are meaningless if used together. 118.Pp 119.Nm Timed 120checks for a master time server on each network to which 121it is connected, except as modified by the 122.Fl n 123and 124.Fl i 125options described above. 126If it finds masters on more than one network, it chooses one network 127on which to be a "slave," and then periodically checks the other 128networks to see if the masters there have disappeared. 129.Pp 130One way to synchronize a group of machines is to use an NTP daemon to 131synchronize the clock of one machine to a distant standard or a radio 132receiver and 133.Fl F Ar hostname 134to tell its timed daemon to trust only itself. 135.Pp 136Messages printed by the kernel on the system console occur with 137interrupts disabled. 138This means that the clock stops while they are printing. 139A machine with many disk or network hardware problems and consequent 140messages cannot keep good time by itself. Each message typically causes 141the clock to lose a dozen milliseconds. A time daemon can 142correct the result. 143.Pp 144Messages in the system log about machines that failed to respond 145usually indicate machines that crashed or were turned off. 146Complaints about machines that failed to respond to initial time 147settings are often associated with "multi-homed" machines 148that looked for time masters on more than one network and eventually 149chose to become a slave on the other network. 150.SH WARNING 151If two or more time daemons, whether 152.Nm timed , 153.Xr NTP , 154try to adjust the same clock, temporal chaos will result. 155If both 156.Nm 157and another time daemon are run on the same machine, 158ensure that the 159.Fl F 160flag is used, so that 161.Nm timed 162never attempts to adjust the local clock. 163.Pp 164The protocol is based on UDP/IP broadcasts. All machines within 165the range of a broadcast that are using the TSP protocol must cooperate. 166There cannot be more than a single administrative domain using the 167.Fl F 168flag among all machines reached by a broadcast packet. 169Failure to follow this rule is usually indicated by complaints concerning 170"untrusted" machines in the system log. 171.Sh FILES 172.Bl -tag -width /var/log/timed.masterlog -compact 173.It Pa /var/log/timed.log 174tracing file for timed 175.It Pa /var/log/timed.masterlog 176log file for master timed 177.El 178.Sh SEE ALSO 179.Xr date 1 , 180.Xr adjtime 2 , 181.Xr gettimeofday 2 , 182.Xr icmp 4 , 183.Xr timedc 8 , 184.Rs 185.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD" 186.%A R. Gusella 187.%A S. Zatti 188.Re 189.Sh HISTORY 190The 191.Nm 192daemon appeared in 193.Bx 4.3 . 194