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TIMED(1M)							     TIMED(1M)

NAME    [Toc]    [Back]

     timed - time server daemon

SYNOPSIS    [Toc]    [Back]

     /usr/etc/timed [ -tdM ] [ -G netgroup] [ -F host1 host2 ...]
	 [ -n network ]	[ -i network ] [ -P param-file ]

DESCRIPTION    [Toc]    [Back]

     Timed is a	time server daemon and is normally invoked at boot time	from
     the /etc/init.d/network file.  It synchronizes the	host's time with the
     time of other machines in a local area network running timed.  These time
     servers will slow down the	clocks of some machines	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.

     Timed communicates	with the date(1) command in order to set the date
     globally.	Adjustments made by the	date command are accumulated by	the
     time daemon with all other	adjustments.  This means that timed can
     automatically adjust the system clock on an isolated machine, not
     connected to a network.  The adjustments from the date command change the
     timetrim parameter	described below.

     The service provided by timed 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.	The
     master adjusts its	own clock by averaging the clocks of all trusted
     machines (see below) with its own clock.  If the machine running the
     master crashes, then the slaves elect a new master	from among slaves
     running with the -M flag.	A timed	running	without	the -M,	-F, or -G
     flags will	remain a slave.

     Note that "master-slave" suggests things to many people that are not
     true.  A better word than "master"	is "moderator."	 Unless	the clock of
     the so called master is extremely bad, the	time it	distributes to the so
     called slaves is the median of all	of the slaves.	As long	as the so
     called master can keep time for the few seconds from when it starts to
     measure the current time of all of	the slaves until it sends the
     difference	between	each slave's clock and the median, the master's	clock
     is	fine.  Bad clocks are treated the same whether they are	on the master
     or	a slave.  Times	that are very different	from the median	are discarded,
     and then the median of the	remaining times	is computed and	used.  For
     that reason, it is	practically always wrong to run	timed without the -M

     Timed logs	accumulated corrections	in the system log (see syslogd(1M)) to
     ease adjusting the	local clock.  The clock	can be adjusted	by changing
     the timetrim parameter using systune(1M) or with the syssgi(2) system
     call.  This parameter is used by the operating system to compensate for
     variations	among machines.	 It can	be used	to improve the accuracy	of the

									Page 1

TIMED(1M)							     TIMED(1M)

     local clock.  -P param-file specifies a file in which to save a computed
     value of the timetrim parameter.  The active value	in the operating
     system is set to the value	found in the file when the daemon started.  An
     error message is displayed	when the daemon	is first started if the	file
     contains nonsense.	 However, a corrected value will be placed in the file
     during its	normal updates.	 A good	choice for the file name is

     The -F flag means only the	local machine and the machines host1, host2,
     etc., are trusted to have good hardware clocks and	to be securely
     administered.  Any	attempts to change the clocks by other,	untrusted
     machines are ignored, except to log them in the system log.  The clocks
     of	untrusted machines are not averaged by the master if the master	is the
     only trusted machine.  Untrusted clocks that are close to the clock of
     the master	are used if there is more than one trusted master active.  A
     master which has been told	it is trustworthy will tell untrustworthy
     machines which try	to be elected master to	be quiet, to "squash" them.

     A machine without the -G or -F flags trusts all other machines as much as
     it	trusts itself.

     The clock of a daemon started with	-F localhost and without -G "free
     runs." In other words, if the machine does	not trust any other machines,
     it	does not try to	adjust its own clock.

     The -G flag is used to specify a netgroup (see netgroup(4)) of trusted
     machines.	This flag allows central administration	of the list of trusted
     machines.	Making gateways	trusted	ties the clocks	in an internet
     together, because after a network partition is healed, the	trusted
     gateways will suppress the	upstart	local master elected during the

     Timed requests synchronization service from the first master server
     located.  If permitted by the -M flag, it will provide synchronization
     service on	any attached networks on which no current master server	was
     detected.	Such a server propagates the time computed by the top-level
     master.  The -n flag, followed by the name	of a network which the host is
     connected to (see networks(4)), overrides the default choice of the
     network addresses made by the program.  Each time the -n flag appears,
     that network name is added	to a list of valid networks.  All other
     networks are ignored.  The	-i flag, followed by the name of a network to
     which the host is connected (see networks(4)), overrides the default
     choice of the network addresses made by the program.  Each	time the -i
     flag appears, that	network	name is	added to a list	of networks to ignore.
     All other networks	are used by the	time daemon.  The -n and -i flags are
     meaningless if used together.

     The -t flag causes	timed to trace the messages it receives	in the file
     /var/adm/timed.log.  Tracing can be turned	on or off by the program
     timedc(1M).  Beware that the log file grows very quickly in a large

									Page 2

TIMED(1M)							     TIMED(1M)

     The -d flag is for	debugging the daemon.  It causes the program to	not
     put itself	into the background.

     Timed checks for a	master time server on each network to which it is
     connected,	except as modified by the -n and -i options described above.
     If	it finds masters on more than one network, it chooses one network on
     which to be a "slave," and	then periodically checks the other networks to
     see if the	masters	there have disappeared.

     The timeslave(1M) daemon can be used to inexpensively synchronize the
     clock on a	machine	to the clock on	a remote machine.  It does not require
     any daemons or special programs on	the remote machine.

     One way to	synchronize a group of IRIS's is to use	timeslave to
     synchronize the clock of one machine to a distant standard	or a radio
     receiver and -F hostname to tell its timed	daemon to trust	only itself.

     Messages printed by the kernel on the system console occur	with
     interrupts	disabled.  This	means that the clock stops while they are
     printing.	A machine with many disk or network hardware problems and
     consequent	messages cannot	keep good time by itself.  Each	message
     typically causes the clock	to lose	a dozen	milliseconds.  A time daemon
     can correct the result, but will compute a	bogus timetrim value.

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

WARNING    [Toc]    [Back]

     If	two or more time daemons, whether timed, timeslave, or NTP, try	to
     adjust the	same clock, temporal chaos will	result.	 If both timed and
     timeslave are run on the same machine, ensure that	the -G flag is not
     used but that the -F flag is used,	so that	timed never attempts 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 or
     -G	flags 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    [Toc]    [Back]

     /var/adm/timed.log		  tracing file for timed
     /var/adm/SYSLOG		  system log
     /etc/init.d/network	  start-up script
     /etc/config/timed.options	  optional flags, by default
				  "-G timelords	-P /var/adm/timetrim"
     /var/adm/timetrim		  default file for timetrim accumulation

									Page 3

TIMED(1M)							     TIMED(1M)

SEE ALSO    [Toc]    [Back]

     chkconfig(1M), date(1), adjtime(2), gettimeofday(2), icmp(4P),
     timedc(1M), timeslave(1M),	systune(1M)

									PPPPaaaaggggeeee 4444
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