In this tutorial we will learn how to install, configure and use NTP to synchronize the system clock on CentOS.

Tutorial Topology :

Working Internet Connection

Installation :

To install NTP, type the following command :

yum install ntp

Configuration :

To ensure that the NTP client start at boot time, let add it into config for level 3, 4 and 5 by typing the following command :

chkconfig --level 345 ntpd on

Synchronization :

To synchronize the system clock with the Internet (such as NTP.org), type the following command :

ntpdate 0.centos.pool.ntp.org

Manage the NTP Service :

To start the NTP service, type the following command:

/sbin/service ntpd start

To restart the NTP service, type the following command:

/sbin/service ntpd restart

To stop the NTP service, type the following command:

/sbin/service ntpd stop

Miscellaneous :

You could also setup a cron with crontab to run the ntpdate at a specific interval at your convenience. Don’t forget to make sure that you have a working Internet Connection and that proper firewall rule have been added to allow the traffic, otherwise it might not work properly.