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