NTP time server synchronizes different host time

Network Time Protocol (NTP) is used to synchronize the system time of different hosts on the network. All the hosts you manage can synchronize their time with a designated time server called an NTP server. On the other hand, an NTP server will synchronize its time with any public NTP server, or your chosen server. All system clocks managed by NTP are synchronized to the exact millisecond level.

NTP is the Network Time Protocol. It is a protocol used to synchronize the time of each computer in the network. OpenNTPD is a Unix system network time protocol (NTP) open source program that synchronizes the local clock of a computer system with a remote NTP server. It can also serve as an NTP server for NTP-compliant clients.

In a corporate environment, if they do not want to turn on the firewall for NTP transmission, it is necessary to set up an internal NTP server and then let employees use internal servers instead of public NTP servers. In this guide we will describe how to configure a CentOS system as an NTP server. Before introducing the details, let us first briefly understand the concept of NTP.

Why do we need NTP?

Due to the variety of manufacturing processes, all (non-atomic) clocks do not walk at exactly the same speed. Some clocks are faster and others are slower. Therefore, after a long time, the time of one clock slowly shifts from the others, which is often referred to as "clock drift" or "time drift." In order to minimize the effects of clock drift, hosts using NTP should periodically interact with designated NTP servers to keep their clocks synchronized.

Time synchronization between different hosts is very important for planning backups, intrusion detection records, distributed task scheduling, or transaction order management. It should even be part of the daily task.

By default, the NTP server allows queries from all hosts. If you want to filter incoming NTP synchronization connections, you can add rule filtering traffic to your firewall.

In short, NTP is a protocol for synchronizing clocks on all your hosts. We have already explained how to set up an NTP server and synchronize the time between NTP-capable devices and servers.