MAN page from Mandrake Other timed-0.10-3.i386.rpm

TIMED

Section: Maintenance Commands (8)
Index
BSD mandoc
BSD 4.3

NAME

timed - time server daemon

SYNOPSIS

timed[-M][-t][-d][-i network][-n network][-F host1 host2 ...]

DESCRIPTION

Thisis a time server daemon and is normally invokedat boot time from therc(8)file. It synchronizes the host's time with the time of othermachines in a local area network running timed 8 These time servers will slow down the clocks of some machinesand speed up the clocks of others to bring them to the average network time.The average network time is computed from measurements of clock differencesusing theICMPtimestamp request message.

The service provided bytimedis based on a master-slavescheme.Whentimed 8is started on a machine, it asks the master for the network timeand sets the host's clock to that time.After that, it accepts synchronization messages periodically sent bythe master and calls adjtime(2)to perform the needed corrections on the host's clock.

It also communicates withdate(1)in order to set the date globally,and with timedc(8),a timed control program.If the machine running the master crashes, then the slaves will electa new master from among slaves running with the -Mflag.Atimedrunning without the-Mor-Fflags will remain a slave.The -tflag enablestimedto trace the messages it receives in thefile/var/log/timed.log Tracing can be turned on or off by the programtimedc(8).The-dflag is for debugging the daemon.It causes the program to not put itself into the background.Normallytimedchecks for a master time server on each network to whichit is connected, except as modified by the options described below.It will request synchronization service from the first master serverlocated.If permitted by the-Mflag, it will provide synchronization service on any attached networkson which no current master server was detected.Such a server propagates the time computed by the top-level master.The -nflag, followed by the name of a network which the host is connected to(seenetworks(5)),overrides the default choice of thenetwork addresses made by the program.Each time the-nflag appears, that network name is added to a list of valid networks.All other networks are ignored.The -iflag, followed by the name of a network to which the host is connected(seenetworks(5)),overrides the default choice of the network addresses made by the program.Each time the-iflag appears, that network name is added to a list of networks to ignore.All other networks are used by the time daemon.The-nand -iflags are meaningless if used together.

Timedchecks for a master time server on each network to whichit is connected, except as modified by the-nand-ioptions described above.If it finds masters on more than one network, it chooses one networkon which to be a "slave," and then periodically checks the othernetworks to see if the masters there have disappeared.

One way to synchronize a group of machines is to use an NTP daemon to synchronize the clock of one machine to a distant standard or a radioreceiver and -F hostnameto tell its timed daemon to trust only itself.

Messages printed by the kernel on the system console occur withinterrupts disabled. This means that the clock stops while they are printing.A machine with many disk or network hardware problems and consequentmessages cannot keep good time by itself. Each message typically causesthe clock to lose a dozen milliseconds. A time daemon cancorrect the result.

Messages in the system log about machines that failed to respondusually indicate machines that crashed or were turned off.Complaints about machines that failed to respond to initial timesettings are often associated with ``multi-homed''machines that looked for time masters on more than one network and eventuallychose to become slaves on other networks.

WARNINGS

If two or more time daemons, whether timed orntp,try to adjust the same clock, temporal chaos will result.If both timedand another time daemon are run on the same machine,ensure that the -Fflag is used, so that timednever attempts to adjust the local clock.

The protocol is based on UDP/IP broadcasts. All machines withinthe range of a broadcast that are using the TSP protocol must cooperate.There cannot be more than a single administrative domain using the-Fflag among all machines reached by a broadcast packet.Failure to follow this rule is usually indicated by complaints concerning``untrusted''machines in the system log.

FILES

/var/log/timed.log: tracing file for timed
/var/log/timed.masterlog: log file for master timed

HISTORY

Thetimeddaemon appeared inBSD 4.3

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