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NTPD(8) BSD 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 2030, and the Network Time
Protocol version 3, as described in RFC 1305.
ntpd uses the adjtime(2) system call to correct the local system time
without causing time jumps. Adjustments larger than 128ms 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
option, all calls to adjtime(2) will be logged.
When ntpd starts up, it reads settings from a configuration file, typi-
cally ntpd.conf(5).
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 Set the time immediately at startup if the local clock is off
by more than 180 seconds. Allows for a large time correc-
tion, eliminating the need to run rdate(8) before starting
ntpd.
-v This option allows ntpd to send DEBUG priority messages to
syslog.
When ntpd receives a SIGINFO signal, it will write its peer and sensor
status to syslog.
FILES
/etc/ntpd.conf default ntpd configuration file
/var/db/ntpd.drift drift file, written by ntpd periodically and used
at startup to get the initial clock drift
SEE ALSO
date(1), adjfreq(2), adjtime(2), ntpd.conf(5), rdate(8), timed(8)
Network Time Protocol (Version 3), RFC 1305, March 1992.
Simple Network Time Protocol (SNTP) Version 4, RFC 2030, October 1996.
HISTORY
The ntpd program first appeared in OpenBSD 3.6.
BSD April 6, 2008 BSD
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