ntpd: Network Time Protocol (NTP) Daemon User’s Manual

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ntpd: Network Time Protocol (NTP) Daemon User Manual

The ntpd program is an operating system daemon that synchronizes the system clock to remote NTP time servers or local reference clocks. It is a complete implementation of NTP version 4 defined by RFC-5905, but also retains compatible with version 3 defined by RFC-1305 and versions 1 and 2, defined by RFC-1059 and RFC-1119, respectively. The program can operate in any of several modes, including client/server, symmetric and broadcast modes, and with both symmetric-key and public-key cryptography.

This document applies to version 4.2.8p10 of ntpd.

Short Table of Contents


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1 Description

The ntpd program ordinarily requires a configuration file described at ‘ntp.conf’. This configuration file contains configuration commands described on the pages listed above. However a client can discover remote servers and configure them automatically. This makes it possible to deploy a fleet of workstations without specifying configuration details specific to the local environment.

The ntpd program normally operates continuously while adjusting the system time and frequency, but in some cases this might not be practical. With the -q option ntpd operates as in continuous mode, but exits just after setting the clock for the first time. Most applications will probably want to specify the iburst option with the server command. With this option an initial volley of messages is exchanged to groom the data and set the clock in about ten seconds’ time. If nothing is heard after a few minutes’ time, the daemon times out and exits without setting the clock.


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1.1 Usage

WhatDefaultFlagOption
configuration file/etc/ntp.conf-cconffile
frequency filenone-fdriftfile
leapseconds filenoneleapfile
process ID filenone-ppidfile
log filesystem log-llogfile
include filenonenoneincludefile
statistics path/var/NTP-sstatsdir
keys path/usr/local/etc-kkeysdir