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

     ntpd -- Network Time Protocol daemon

     ntpd [-dnSsv] [-f file]

     The ntpd daemon synchronizes the local clock to one or more remote	NTP
     servers or	local timedelta	sensors.  ntpd can also	act as an NTP server
     itself, redistributing the	local time.  It	implements the Simple Network
     Time Protocol version 4, as described in RFC 5905,	and the	Network	Time
     Protocol version 3, as described in RFC 1305.  Time can also be fetched
     from TLS HTTPS servers to reduce the impact of unauthenticated NTP	man-
     in-the-middle attacks.

     The options are as	follows:

     -d		 Do not	daemonize.  If this option is specified, ntpd will run
		 in the	foreground and log to stderr.

     -f	file	 Use file as the configuration file, instead of	the default

     -n		 Configtest mode.  Only	check the configuration	file for va-

     -S		 Cancel	the effect of the -s flag.

     -s		 Always	try to set the time at startup.	 By default ntpd at-
		 tempts	to set the time	at boot	only if	constraints are	con-
		 figured and satisfied,	and the	clock should be	moved forward.

		 ntpd will stay	in the foreground for up to 15 seconds waiting
		 for one of the	configured NTP servers to reply.

     -v		 This option allows ntpd to send DEBUG priority	messages to

     ntpd uses the adjtime(2) system call to correct the local system time
     without causing time jumps.  Adjustments of 32ms and greater are logged
     using syslog(3).  The threshold value is chosen to	avoid having local
     clock drift thrash	the log	files.	Should ntpd be started with the	-d or
     -v	option,	all calls to adjtime(2)	will be	logged.

     After the local clock is synchronized, ntpd adjusts the clock frequency
     using the adjfreq(2) system call to compensate for	systematic drift.

     ntpd is started at	boot time by default via ntpd_flags in /etc/rc.conf.
     See rc(8) and rc.conf(8) for more information on the boot process and en-
     abling daemons.

     When ntpd starts up, it reads settings from its configuration file, typi-
     cally ntpd.conf(5), and its initial clock drift from /var/db/ntpd.drift.
     Clock drift is periodically written to the	drift file thereafter.

     /etc/ntpd.conf	    Default configuration file.
     /var/db/ntpd.drift	    Drift file.
     /var/run/ntpd.sock	    Socket file	for communication with ntpctl(8).

     date(1), adjfreq(2), adjtime(2), ntpd.conf(5), ntpctl(8), rc(8),
     rc.conf(8), rdate(8)

     David L. Mills, Network Time Protocol (Version 3):	Specification,
     Implementation and	Analysis, RFC 1305, March 1992.

     David L. Mills, Jim Martin, Jack Burbank, and William Kasch, Network Time
     Protocol Version 4: Protocol and Algorithms Specification,	RFC 5905, June

     The ntpd program first appeared in	OpenBSD	3.6.

FreeBSD	13.0			 June 20, 2019			  FreeBSD 13.0


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