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

NAME
     ntpd -- Network Time Protocol daemon

SYNOPSIS
     ntpd [-dnSsv] [-f file]

DESCRIPTION
     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
		 /etc/ntpd.conf.

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

     -S		 Do not	set the	time immediately at startup.  This is the
		 default.

     -s		 Try to	set the	time immediately at startup, as	opposed	to
		 slowly	adjusting the clock.  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
		 syslog.

     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 usually started at	boot time, and can be enabled by setting
     ntpd_flags	in /etc/rc.conf.local.	See rc(8) and rc.conf(8) for more
     information on the	boot process and enabling 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.

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

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

STANDARDS
     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
     2010.

HISTORY
     The ntpd program first appeared in	OpenBSD	3.6.

FreeBSD	11.1			 June 24, 2017			  FreeBSD 11.1

NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | STANDARDS | HISTORY

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