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.

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. Allows for a large time correction, eliminating the need to run rdate(8) before starting ntpd.

-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 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.

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, typically ntpd.conf(5), and its initial clock drift from /var/db/ntpd.drift. Clock drift is periodically written to the drift file thereafter.

When ntpd receives a SIGINFO signal, it writes its peer and sensor status to syslog(3).

FILES
/etc/ntpd.conf
    Default configuration file.
/var/db/ntpd.drift
    Drift file.

SEE ALSO
date(1), adjfreq(2), adjtime(2), ntpd.conf(5), rc(8), rc.conf(8), rdate(8), timed(8) RFC 1305, Network Time Protocol (Version 3), March 1992. RFC 2030, Simple Network Time Protocol (SNTP) Version 4, October 1996.

HISTORY
The ntpd program first appeared in OpenBSD 3.6.