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TIMED(8)		  BSD System Manager's Manual		      TIMED(8)

     timed -- time server daemon

     timed [-dtM] [-i network |	-n network] [-F	host ...]

     The timed utility is a time server	daemon which is	normally invoked at
     boot time from the file.  It	synchronizes the host's	time
     with the time of other machines, which are	also running timed, in a local
     area network.  These time servers will slow down the clocks of some ma-
     chines and	speed up the clocks of others to bring them to the average
     network time.  The	average	network	time is	computed from measurements of
     clock differences using the ICMP timestamp	request	message.

     The following options are available:

     -d	     Enable debugging mode; do not detach from the terminal.

     -i	network
	     Add network to the	list of	networks to ignore.  All other net-
	     works to which the	machine	is directly connected are used by
	     timed.  This option may be	specified multiple times to add	more
	     than one network to the list.

     -F	host ...
	     Create a list of trusted hosts.  The timed	utility	will only ac-
	     cept trusted hosts	as masters.  If	it finds an untrusted host
	     claiming to be master, timed will suppress	incoming messages from
	     that host and call	for a new election.  This option implies the
	     -M	option.	 If this option	is not specified, all hosts on the
	     connected networks	are treated as trustworthy.

     -M	     Allow this	host to	become a timed master if necessary.

     -n	network
	     Add network to the	list of	allowed	networks.  All other networks
	     to	which the machine is directly connected	are ignored by timed.
	     This option may be	specified multiple times to add	more than one
	     network to	the list.

     -t	     Enable tracing of received	messages and log to the	file
	     /var/log/timed.log.  Tracing can be turned	on or off while	timed
	     is	running	with the timedc(8) utility.

     The -n and	-i flags are mutually exclusive	and require as arguments real
     networks to which the host	is connected (see networks(5)).	 If neither
     flag is specified,	timed will listen on all connected networks.

     A timed running without the -M nor	-F flags will always remain a slave.
     If	the -F flag is not used, timed will treat all machines as trustworthy.

     The timed utility is based	on a master-slave scheme.  When	timed is
     started on	a machine, it asks the master for the network time and sets
     the host's	clock to that time.  After that, it accepts synchronization
     messages periodically sent	by the master and calls	adjtime(2) to perform
     the needed	corrections on the host's clock.

     It	also communicates with date(1) in order	to set the date	globally, and
     with timedc(8), a timed control utility.  If the machine running the mas-
     ter becomes unreachable, the slaves will elect a new master from among
     those slaves which	are running with at least one of the -M	and -F flags.

     At	startup	timed normally checks for a master time	server on each network
     to	which it is connected, except as modified by the -n and	-i options de-
     scribed above.  It	will request synchronization service from the first
     master server located.  If	permitted by the -M or -F flags, it will pro-
     vide synchronization service on any attached networks on which no trusted
     master server was detected.  Such a server	propagates the time computed
     by	the top-level master.  The timed utility will periodically check for
     the presence of a master on those networks	for which it is	operating as a
     slave.  If	it finds that there are	no trusted masters on a	network, it
     will begin	the election process on	that network.

     One way to	synchronize a group of machines	is to use ntpd(8) to synchro-
     nize the clock of one machine to a	distant	standard or a radio receiver
     and -F hostname to	tell its timed to trust	only itself.

     Messages printed by the kernel on the system console occur	with inter-
     rupts disabled.  This means that the clock	stops while they are printing.
     A machine with many disk or network hardware problems and consequent mes-
     sages cannot keep good time by itself.  Each message typically causes the
     clock to lose a dozen milliseconds.  A time daemon	can correct the	re-

     Messages in the system log	about machines that failed to respond usually
     indicate machines that crashed or were turned off.	 Complaints about ma-
     chines that failed	to respond to initial time settings are	often associ-
     ated with "multi-homed" machines that looked for time masters on more
     than one network and eventually chose to become a slave on	the other net-

     Temporal chaos will result	if two or more time daemons attempt to adjust
     the same clock.  If both timed and	another	time daemon are	run on the
     same machine, ensure that the -F flag is used, so that timed never	at-
     tempts to adjust the local	clock.

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

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

     date(1), adjtime(2), gettimeofday(2), icmp(4), networks(5), ntpd(8),

     R.	Gusella	and S. Zatti, TSP: The Time Synchronization Protocol for UNIX

     The timed utility appeared	in 4.3BSD.

BSD				 June 6, 1993				   BSD


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