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Computer Time Synchronization
A Beginner's Guide to Network Time Protocol (NTP)

Warning! This Section is known to contain obsolete information.

When this section was written there was no cross platform time synchronization software installed as part of the OS on any computer that I was aware of. Timed would synchronize the time of Unix computers on a LAN, but not necessarily to the correct time. Today nearly all computers come with network time synchornization software installed. It nomally synchronizes with accurate servers on the Internet but not with other computers on your LAN and not normally cross platform. Many Unix like computers include a crippled version of NTP. The full version of NTP remains the best solution for the users who want or need both accurate time and tight synchronization of all computers on their LAN.

A tutorial on how-to install free Network Time Protocol (NTP) servers and clients on UNIX (OpenBSD and Linux) and Windows to synchronize the time on all your computers to within less than a second of the official Coordinated Universal Time (UTC). Quick start by skipping the background and jumping to the NTP what and how. The emphasis is on the basics of installing Network Time Protocol servers on UNIX and Windows computers with numerous links to detailed authoritative sources.

Other Time Software discusses products tried before turning to Network Time Protocol. These include UNIX's timed and NIST's free Windows clients. It's become clear that NTP Is a Complete Solution to the UNIX and Windows computer time synchronization and accuracy problem. The open source Network Time Protocol server, ntpd, is complex, and the extensive and highly technical documentation at the official University of Delaware NTP site, is not oriented to the practical issues of getting NTP servers to work with a minumum of time and effort.

You can skip the previous pages but not What NTP Does and How It Works or Selecting Public NTP servers which cover the minimum concepts and networking background necessary to use NTP. Installing Network Time Protocol software is trivial compared to figuring out what you're going to connect it to; these pages explain the relationships between NTP servers and how to select public servers to act as your time sources.

Installing NTP on Unix gives step by step instructions for installing ntpd, the open source and free Network Time Protocol server, on UNIX, specifically OpenBSD 2.6, 2.7, 2.8 and 2.9 and also Red Hat Linux 6.2 and 7.1. As the instructions are identical they should work on any similar system and anyone familiar with UNIX should be able to make the minor directory adjustments that may be necessary. Minimum configuration file contents and useable command line options are provided and explained.

Installing NTP on Windows covers four products. All are free, including commercial use, and one is true open source. There are two client only products for all Windows platforms from 95 to ME and 2000. The open source, NetTime implements SNTP and will act as a client and or server on all Windows platforms. Obtaining latest builds and installing ntpd, a complete NTP implementation for Windows NT and 2000 is covered. Ntpd runs as a service and includes both client and server options but is configured via a text file (sorry no GUI control panel).

Choices on Other Operating Systems points you to pages that list software for other platforms and Conclusion offers a few final thoughts on Network Time Protocol and ntpd, a first rate example of open source software.

Note: Because this section now contains disclaimers that infomation is or may be obsolete, in no way implies pages without such disclaimers are necessarily up-to-date. Most of this site was written between 2000 and 2002. Basics are much the same but details have changed. Information is provided as is.

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