ntpd

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

NAME
     ntpd — Network Time Protocol daemon

SYNOPSIS
     ntpd [-dnSsv] [-f file] [-p 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.

     -p file     Write pid to file

     -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 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
     enabling daemons.

     When ntpd starts up, it reads settings from its configuration file,
     typically 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.

BSD                            September 6, 2017                           BSD