Use timedatectl and timesyncd

Server Guide
#1

Ubuntu uses timedatectl and timesyncd for synchronising time, and they are installed by default as part of systemd. You can optionally use chrony to serve the Network Time Protocol.

In this guide, we will show you how to configure these services.

Note:
If chrony is installed, timedatectl steps back to let chrony handle timekeeping. This ensures that no two time-syncing services will be in conflict.

Check status of timedatectl

The current status of time and time configuration via timedatectl and timesyncd can be checked with the timedatectl status command, which will produce output like this:

               Local time: Wed 2023-06-14 12:05:11 BST
           Universal time: Wed 2023-06-14 11:05:11 UTC
                 RTC time: Wed 2023-06-14 11:05:11
                Time zone: Europe/Isle_of_Man (BST, +0100)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

If chrony is running, it will automatically switch to:

[...]
 systemd-timesyncd.service active: no

Configure timedatectl

By using timedatectl, an admin can control the timezone, how the system clock should relate to the hwclock and whether permanent synchronisation should be enabled. See man timedatectl for more details.

Check status of timesyncd

timesyncd itself is a normal service, so you can check its status in more detail using:

systemctl status systemd-timesyncd

The output produced will look something like this:

      systemd-timesyncd.service - Network Time Synchronization
       Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: enabled)
       Active: active (running) since Fri 2018-02-23 08:55:46 UTC; 10s ago
         Docs: man:systemd-timesyncd.service(8)
     Main PID: 3744 (systemd-timesyn)
       Status: "Synchronized to time server 91.189.89.198:123 (ntp.ubuntu.com)."
        Tasks: 2 (limit: 4915)
       CGroup: /system.slice/systemd-timesyncd.service
               |-3744 /lib/systemd/systemd-timesyncd
    
    Feb 23 08:55:46 bionic-test systemd[1]: Starting Network Time Synchronization...
    Feb 23 08:55:46 bionic-test systemd[1]: Started Network Time Synchronization.
    Feb 23 08:55:46 bionic-test systemd-timesyncd[3744]: Synchronized to time server 91.189.89.198:123 (ntp.ubuntu.com).

Configure timesyncd

The server from which to fetch time for timedatectl and timesyncd can be specified in /etc/systemd/timesyncd.conf. Additional config files can be stored in /etc/systemd/timesyncd.conf.d/. The entries for NTP= and FallbackNTP= are space-separated lists. See man timesyncd.conf for more details.

Next steps

If you would now like to serve the Network Time Protocol via crony, this guide will walk you through how to install and configure your setup.

References

Ubuntu Server documentation
Ubuntu Server how-to guides
About time synchronisation