NTP (Network Time Protocol) is the established standard for time synchronization of digital devices such as clients or servers. This page provides an updated overview of the current state of the art.
The currently valid version is NTPv4, defined in RFC 5905, and remains backward compatible with NTPv3.
Standard Port: 123 (usually via UDP, optionallyased Systems
The service systemd-timesyncd is installed by default on many systems and implements the SNTP (Simple NTP) protocol. For simple clients, this is usually sufficient.
More information: https://www.freedesktop.org/software/systemd/man/systemd-timesyncd.service.html systemd-timesyncd Documentation
service systemd-timesyncd statustimedatectl set-ntp true|falsetimedatectl timesync-statusAlternatively on older systems:
timedatectl statusConfiguration is done via:
/etc/systemd/timesyncd.confor via additional files in:
/etc/systemd/timesyncd.conf.d/*.confDetails on configuration: https://www.freedesktop.org/software/systemd/man/timesyncd.conf.html timesyncd.conf Documentation
Chrony is the preferred NTP client in modern distributions such as RedHat 8 and Ubuntu 25.10. It offers advanced features and supports Network Time Security (NTS) for encrypted time synchronization.
systemctl enable chronyd
nano /etc/chrony.confAdd a new line:
server <NTPServerIP>Then check:
systemctl restart chronyd
chronyc sourcesIn Windows Server environments, the Primary Domain Controller (PDC) usually acts as the NTP time source. Configuration is done via Group Policies or Registry settings.
The service Windows Time uses NTPv3 by default and is compatible with SNTP clients and servers.
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