How To Use Proxmox NTP in a Cluster Setup

Using Custom NTP Servers

In some cases, it might be desired to not use the default NTP servers. For example, if your Proxmox VE nodes do not have access to the public internet (e.g., because of restrictive firewall rules), you need to setup local NTP servers and tell systemd-timesyncd to use them:

File /etc/systemd/timesyncd.conf

[Time]
NTP=ntp1.example.com ntp2.example.com ntp3.example.com ntp4.example.com

After restarting the synchronization service (systemctl restart systemd-timesyncd) you should verify that your newly configured NTP servers are used by checking the journal (journalctl — since -1h -u systemd-timesyncd):

...
Oct 07 14:58:36 node1 systemd[1]: Stopping Network Time Synchronization...
Oct 07 14:58:36 node1 systemd[1]: Starting Network Time Synchronization...
Oct 07 14:58:36 node1 systemd[1]: Started Network Time Synchronization.
Oct 07 14:58:36 node1 systemd-timesyncd[13514]: Using NTP server 10.0.0.1:123 (ntp1.example.com).
Oct 07 14:58:36 nora systemd-timesyncd[13514]: interval/delta/delay/jitter/drift 64s/-0.002s/0.020s/0.000s/-31ppm
...

That’s it.