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Comparison of different NTP Services



Network Time Protocol (NTP) is a protocol used to synchronize the clocks of computer systems over a network. Accurate time synchronization is crucial for many applications such as financial transactions, data logging, and scientific computing. There are several NTP implementations available, and in this blog post, we will discuss the differences between some of the most popular ones.

chrony ntp openntpd
Supported systems Linux, FreeBSD, NetBSD, illumos, macOS Linux, FreeBSD, NetBSD, OpenBSD, Solaris, macOS, Windows, …​ Linux, FreeBSD, NetBSD, OpenBSD, Solaris, macOS
License GPLv2 MIT + BSD BSD
Programming language C C C
Size of stripped daemon binary in default configuration in Linux x86-64 287 KB 889 KB 92 KB


Chrony is a modern implementation of NTP that was designed to overcome some of the limitations of the older implementations like NTPd. Chrony uses a more accurate algorithm to calculate the clock offsets and supports more sources of time data, including GPS and radio clocks. It also has a hybrid mode that combines the best features of NTP and PTP to achieve even higher accuracy. Chrony is known for its stability and reliability, making it a popular choice for critical systems.


NTPd is the reference implementation of NTP and has been the standard for many years. It is a mature and stable implementation that is widely used in production environments. NTPd supports a wide range of operating systems and hardware architectures, making it a versatile choice. However, NTPd has been criticized for its complex configuration and lack of support for newer features like leap seconds.


OpenNTPd is a lightweight implementation of NTP that was designed with security in mind. It has a simple and easy-to-use configuration and supports only the essential NTP features. OpenNTPd uses privilege separation to minimize the risk of exploitation by attackers. However, OpenNTPd has limited support for monitoring and logging, which makes it less suitable for large-scale deployments.


Choosing the right NTP implementation depends on the specific needs and requirements of the system. Chrony is an excellent choice for systems that require high accuracy and reliability. NTPd is a mature and stable implementation that is widely used and supported. OpenNTPd is a lightweight and secure implementation that is suitable for smaller systems. Regardless of the choice, accurate time synchronization is critical for the proper functioning of many applications, and NTP implementations play a crucial role in achieving it.

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