3 include::attributes.txt[]
5 The {pve} cluster stack itself relies heavily on the fact that all
6 the nodes have precisely synchronized time. Some other components,
7 like Ceph, also refuse to work properly if the local time on nodes is
10 Time synchronization between nodes can be achieved with the ``Network
11 Time Protocol'' (`NTP`). {pve} uses `systemd-timesyncd` as NTP client
12 by default, preconfigured to use a set of public servers. This setup
13 works out of the box in most cases.
16 Using Custom NTP Servers
17 ~~~~~~~~~~~~~~~~~~~~~~~~
19 In some cases, it might be desired to not use the default NTP
20 servers. For example, if your {pve} nodes do not have access to the
21 public internet (e.g., because of restrictive firewall rules), you
22 need to setup local NTP servers and tell `systemd-timesyncd` to use
25 .File `/etc/systemd/timesyncd.conf`
28 Servers=ntp1.example.com ntp2.example.com ntp3.example.com ntp4.example.com
31 After restarting the synchronization service (`systemctl restart
32 systemd-timesyncd`) you should verify that your newly configured NTP
33 servers are used by checking the journal (`journalctl --since -1h -u
38 Oct 07 14:58:36 node1 systemd[1]: Stopping Network Time Synchronization...
39 Oct 07 14:58:36 node1 systemd[1]: Starting Network Time Synchronization...
40 Oct 07 14:58:36 node1 systemd[1]: Started Network Time Synchronization.
41 Oct 07 14:58:36 node1 systemd-timesyncd[13514]: Using NTP server 10.0.0.1:123 (ntp1.example.com).
42 Oct 07 14:58:36 nora systemd-timesyncd[13514]: interval/delta/delay/jitter/drift 64s/-0.002s/0.020s/0.000s/-31ppm