After We've Install and Configure OpenNTPD server.
We need to make sure our OpenNTPD server is up and running even we trying to query our openNTPD server from other client.

In this tutorial i don't describe how to install and configure OpenNTPD server so if you want to install and configure OpenNTPD, please click this see my tutorial for Install and Configure OpenNTPD server.

Example, I have a linux centos client and i want to sync my local date and time with OpenNTPD server with ntpdate.

What is OpenNTPD ?

OpenNTPD is a Unix system daemon implementing the Network Time Protocol to synchronize the local clock of a computer system with remote NTP servers. It is also able to act as an NTP server to NTP-compatible clients.

OpenNTPD is primarily developed by Henning Brauer as part of the OpenBSD project. Its design goals include being secure (non-exploitable), easy to configure, accurate enough for most purposes and with source code that can be distributed under a BSD license. Its portable version, like that of OpenSSH, is developed as a child project which adds the portability code to the OpenBSD version and releases it separately. The portable version is developed by Darren Tucker.