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NTPDATE(8)		FreeBSD	System Manager's Manual		    NTPDATE(8)

     ntpdate --	set the	date and time via NTP

     ntpdate [-bBdoqsuv] [-a key] [-e authdelay] [-k keyfile] [-o version]
	     [-p samples] [-t timeout] server ...

     Note: The functionality of	this program is	now available in the ntpd(8)
     program.  See the -q command line option in the ntpd(8) page.  After a
     suitable period of	mourning, the ntpdate program is to be retired from
     this distribution.

     ntpdate sets the local date and time by polling the Network Time Protocol
     (NTP) server(s) given as the server arguments to determine	the correct
     time.  It must be run as root on the local	host.  A number	of samples are
     obtained from each	of the servers specified and a subset of the NTP clock
     filter and	selection algorithms are applied to select the best of these.
     Note that the accuracy and	reliability of ntpdate depends on the number
     of	servers, the number of polls each time it is run and the interval
     between runs.

     The following options are available:

     -a	key  Enable the	authentication function	and specify the	key identifier
	     to	be used	for authentication as the argument key.	 The keys and
	     key identifiers must match	in both	the client and server key
	     files.  The default is to disable the authentication function.

     -B	     Force the time to always be slewed	using the adjtime(2) system
	     call, even	if the measured	offset is greater than +-128 ms.  The
	     default is	to step	the time using settimeofday(2) if the offset
	     is	greater	than +-128 ms.	Note that, if the offset is much
	     greater than +-128	ms in this case, it can	take a long time
	     (hours) to	slew the clock to the correct value.  During this
	     time, the host should not be used to synchronize clients.

     -b	     Force the time to be stepped using	the settimeofday(2) system
	     call, rather than slewed (default)	using the adjtime(2) system
	     call.  This option	should be used when called from	a startup file
	     at	boot time.

     -d	     Enable the	debugging mode,	in which ntpdate will go through all
	     the steps,	but not	adjust the local clock.	 Information useful
	     for general debugging will	also be	printed.

     -e	authdelay
	     Specify the processing delay to perform an	authentication func-
	     tion as the value authdelay, in seconds and fraction (see ntpd(8)
	     for details).  This number	is usually small enough	to be negligi-
	     ble for most purposes, though specifying a	value may improve
	     timekeeping on very slow CPU's.

     -k	keyfile
	     Specify the path for the authentication key file as the string
	     keyfile.  The default is /etc/ntp.keys.  This file	should be in
	     the format	described in ntpd(8).

     -o	version
	     Specify the NTP version for outgoint packets as the integer
	     version, which can	be 1 or	2.  The	default	is 3.  This allows
	     ntpdate to	be used	with older NTP versions.

     -p	samples
	     Specify the number	of samples to be acquired from each server as
	     the integer samples, with values from 1 to	8 inclusive.  The
	     default is	4.

     -q	     Query only	- don't	set the	clock.

     -s	     Divert logging output from	the standard output (default) to the
	     system syslog(3) facility.	 This is designed primarily for	conve-
	     nience of cron(8) scripts.

     -t	timeout
	     Specify the maximum time waiting for a server response as the
	     value timeout, in seconds and fraction.  The value	is rounded to
	     a multiple	of 0.2 seconds.	 The default is	1 second, a value
	     suitable for polling across a LAN.

     -u	     Direct ntpdate to use an unprivileged port	for outgoing packets.
	     This is most useful when behind a firewall	that blocks incoming
	     traffic to	privileged ports, and you want to synchronise with
	     hosts beyond the firewall.	 Note that the -d option always	uses
	     unprivileged ports.

     -v	     Be	verbose.  This option will cause ntpdate's version identifica-
	     tion string to be logged.

     ntpdate can be run	manually as necessary to set the host clock, or	it can
     be	run from the host startup script to set	the clock at boot time.	 This
     is	useful in some cases to	set the	clock initially	before starting	the
     NTP daemon	ntpd(8).  It is	also possible to run ntpdate from a cron(8)
     script.  However, it is important to note that ntpdate with contrived
     cron(8) scripts is	no substitute for the NTP daemon, which	uses sophisti-
     cated algorithms to maximize accuracy and reliability while minimizing
     resource use.  Finally, since ntpdate does	not discipline the host	clock
     frequency as does ntpd(8),	the accuracy using ntpdate is limited.

     Time adjustments are made by ntpdate in one of two	ways.  If ntpdate
     determines	the clock is in	error more than	0.5 second it will simply step
     the time by calling the system settimeofday(2) routine.  If the error is
     less than 0.5 seconds, it will slew the time by calling the system
     adjtime(2)	routine.  The latter technique is less disruptive and more
     accurate when the error is	small, and works quite well when ntpdate is
     run by cron(8) every hour or two.

     ntpdate will decline to set the date if an	NTP server daemon (e.g.,
     ntpd(8)) is running on the	same host.  When running ntpdate on a regular
     basis from	cron(8)	as an alternative to running a daemon, doing so	once
     every hour	or two will result in precise enough timekeeping to avoid
     stepping the clock.

     If	NetInfo	support	is compiled into ntpdate, then the server argument is
     optional if ntpdate can find a time server	in the NetInfo configuration
     for ntpd(8).

     /etc/ntp.keys  contains the encryption keys used by ntpdate.


     The slew adjustment is actually 50% larger	than the measured offset,
     since this	(it is argued) will tend to keep a badly drifting clock	more
     accurate.	This is	probably not a good idea and may cause a troubling
     hunt for some values of the kernel	variables kern.clockrate.tick and

FreeBSD	10.3			January	6, 2000			  FreeBSD 10.3


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