Time synchronization with NTP: Basic concept

This document applies to the following products and product versions:

Maintaining an exact and synchronized system time on the computer is a requirement for team work. For example, planning and calendaring applications rely on it to track time correctly and notify users about appointments on time. For clustered applications, individual host machines often require synchronized system time for mutual communication.

The built-in hardware clock is not a reliable time source and manual correction of the system time might cause malfunction of critical applications. That is why the Network Time Protocol (NTP) is designed to synchronize the system time over the network. Its goal is to maintain the absolute time, and use it to synchronize the system time of all machines within a network.

When the NTP service is properly configured, it continuously queries and adjusts the system time with reliable time servers. Typically, home computers and other devices connected to the internet are configured to query a public time server on the internet.

Figure 1: Individual devices querying a public time server #

Conversely, desktop computers and servers that reside inside a corporate subnet are configured to query a dedicated time server within the local network. The time server itself synchronizes its time with a public time server.

Figure 2: Multiple hosts querying an internal time server #

Since SUSE Linux Enterprise Server 15, chrony is the default implementation of NTP. chrony includes two parts:

Using NTP to maintain the exact time has the following benefits: