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04.04.07
Configuring NTP On Your Linux Server
 By
David Evans
The Network Time Protocol (NTP) defines a set of algorithms for the dissemination of time across the Internet.
The NTP protocol can be used to synchronise the system time on your Linux Server with a highly accurate Internet time reference.
This article describes how to configure the Network Time Protocol (NTP) daemon on your Linux server to synchronise with an Internet based NTP server. It also provides a list of well-know public Internet time references.
Obtaining the NTP Source Code Distribution
The Linux NTP source code distribution is publicly available 'open source' software. The distribution can be freely downloaded from the NTP web site 'ntp.org'. The latest NTP version for Linux is 2.4.2. A port is also available for Windows platforms, but the primary development platform for NTP is the Linux operating system. A number of Linux based operating systems such as Mandrake and Redhat offer NTP as an installable RPM package.
Once download is complete, the NTP distribution should be configured and compiled on the host computer.
Configuration of the NTP Daemon
The NTP daemon is configured through entries in the primary NTP configuration file 'ntp.conf'. The NTP configuration file contains a list of commands that instruct the daemon to synchronise with a specified NTP server. NTP servers are specified using the 'server' command followed by the domain name of the server thus:
server ntp2c.mcc.ac.uk server ntp.cis.strath.ac.uk
A number of access control options are also available to restrict the use of your NTP server by network time clients. To only allow machines on your own network to synchronize with the server use:
restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
Alternatively, you can restrict all access to your NTP server with the following command:
restrict default ignore
Multiple directives can be specified to restrict access to a specified range of computers.
Using NTP Authentication
NTP authentication is used by time clients to authenticate the time server to prevent rogue server intervention. NTP authentication is based on encrypted keys. A key is encrypted and sent to the client by the server, where it is unencrypted and checked against the client key to ensure a match.
Continue reading this article.
About the Author:
David Evans is a technical author that specialises in Linux NTP Server synchronisation systems. Find out more about Linux NTP Server systems at: http://www.timetools.co.uk/ntp-servers/ref/linux-ntp-server.htm
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