ntpd - "Network Time Protocol daemon"
ntpd [-dnSsv] [-f file] [-p 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 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) with LOG_INFO priority. 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,
The options are as follows:
-d Do not daemonize. If this option is specified, ntpd will run in
the foreground and log to stderr.
Write pid to file
Use file as the configuration file, instead of the default
-n Configtest mode. Only check the configuration file for
-S Do not set the time immediately at startup. This is the
-s Set the time immediately at startup if the local clock is off by
more than 180 seconds. Allows for a large time correction,
eliminating the need to run rdate(8) before starting .
-v This option allows ntpd to send DEBUG priority messages to
When ntpd receives a SIGUSR1 signal, it will write its peer and
sensor status to syslog.
default ntpd configuration file
drift file, written by ntpd periodically and used at startup to
get the initial clock drift
date(1), adjfreq(2), adjtime(2), ntpd.conf(5), rdate(8), timed(8)
, Network Time Protocol (Version 3), March 1992.
, Simple Network Time Protocol (SNTP) Version 4, October 1996.
The ntpd program first appeared in OpenBSD 3.6 .
$Mdocdate: November 10 2007 $ NTPD(8)