Synchronising the System Time

The reasons are many and good for making sure your servers are all set to the same time. The usual way to synchronise time with Unix is through NTP - Network Time Protocol. The ntpd daemon can operate as a server, a client, or a relay system.

One note here. Whilst researching this topic I found scads and scads of information regarding the setting up of Time Servers. For such an apparently simple concept, it can get very involved. However, what I present here are the basics of getting it installed and running, which is really quite simple, and then it's up to the reader to take it to the next levels, if required.

Prerequisites

efexor.vampiress.net: stratum 3, offset 20.535114, synch distance 0.14081
mel001.pacific.net.au: stratum 2, offset 20.531832, synch distance 0.08061
clock.tl.fukuoka-u.ac.jp: stratum 1, offset 20.523599, synch distance 0.00069,
refid 'GPS'

To start the daemon, edit /etc/rc.conf and add the following line..

vi  /etc/rc.conf

..and reboot the server. The daemon should be running, although it may seem to take a while for it to kick in, for the following reason.

Some references suggest to create a /etc/ntp.drift file, however I tend not to as once started, the system will build its own within an hour. To quote FreeBSD.org's Hypertext Man Pages..

Frequency Discipline

The ntpd behavior at startup depends on whether the frequency file, usually ntp.drift, exists. This file contains the latest estimate of clock frequency error. When the ntpd is started and the file does not exist, the ntpd enters a special mode designed to quickly adapt to the particular system clock oscillator time and frequency error. This takes approximately 15 minutes, after which the time and frequency are set to nominal values and the ntpd enters normal mode, where the time and frequency are continuously tracked relative to the server. After one hour the frequency file is created and the current frequency offset written to it. When the ntpd is started and the file does exist, the ntpd frequency is initialized from the file and enters normal mode immediately. After that the current frequency offset is written to the file at hourly intervals.

Thanks ntpd! Once running, the command line utility ntpq can be used to check the status of the NTP daemon on the local machine (or on a remote host)..

ntpq
ntpq> peers

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*b.pool.ntp.uq.e im-ntp.its.uq.e  2 u  176  256  377  224.489  -116.96  15.090
+levy.catalyst.n gen3.ihug.co.nz  3 u   42  256  377   88.565  -205.22  13.766

Controlling Access to the Server

Links and References