system-timesync.adoc

   1 Time Synchronization
   2 --------------------
   3 ifdef::wiki[]
   4 :pve-toplevel:
   5 endif::wiki[]
   6
   7 The {pve} cluster stack itself relies heavily on the fact that all
   8 the nodes have precisely synchronized time. Some other components,
   9 like Ceph, also refuse to work properly if the local time on nodes is
  10 not in sync.
  11
  12 Time synchronization between nodes can be achieved with the ``Network
  13 Time Protocol'' (`NTP`). {pve} uses `systemd-timesyncd` as NTP client
  14 by default, preconfigured to use a set of public servers. This setup
  15 works out of the box in most cases.
  16
  17
  18 Using Custom NTP Servers
  19 ~~~~~~~~~~~~~~~~~~~~~~~~
  20
  21 In some cases, it might be desired to not use the default NTP
  22 servers. For example, if your {pve} nodes do not have access to the
  23 public internet (e.g., because of restrictive firewall rules), you
  24 need to setup local NTP servers and tell `systemd-timesyncd` to use
  25 them:
  26
  27 .File `/etc/systemd/timesyncd.conf`
  28 ----
  29 [Time]
  30 Servers=ntp1.example.com ntp2.example.com ntp3.example.com ntp4.example.com
  31 ----
  32
  33 After restarting the synchronization service (`systemctl restart
  34 systemd-timesyncd`) you should verify that your newly configured NTP
  35 servers are used by checking the journal (`journalctl --since -1h -u
  36 systemd-timesyncd`):
  37
  38 ----
  39 ...
  40 Oct 07 14:58:36 node1 systemd[1]: Stopping Network Time Synchronization...
  41 Oct 07 14:58:36 node1 systemd[1]: Starting Network Time Synchronization...
  42 Oct 07 14:58:36 node1 systemd[1]: Started Network Time Synchronization.
  43 Oct 07 14:58:36 node1 systemd-timesyncd[13514]: Using NTP server 10.0.0.1:123 (ntp1.example.com).
  44 Oct 07 14:58:36 nora systemd-timesyncd[13514]: interval/delta/delay/jitter/drift 64s/-0.002s/0.020s/0.000s/-31ppm
  45 ...
  46 ----