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 won't work properly if the local time on all nodes is
  10 not in sync.
  11
  12 Time synchronization between nodes can be achieved using the ``Network
  13 Time Protocol'' (`NTP`). As of {pve} 7, `chrony` is used as the default
  14 NTP daemon, while {pve} 6 uses `systemd-timesyncd`. Both come preconfigured to
  15 use a set of public servers.
  16
  17 IMPORTANT: If you upgrade your system to {pve} 7, it is recommended that you
  18 manually install either `chrony`, `ntp` or `openntpd`.
  19
  20 Using Custom NTP Servers
  21 ~~~~~~~~~~~~~~~~~~~~~~~~
  22
  23 In some cases, it might be desired to use non-default NTP
  24 servers. For example, if your {pve} nodes do not have access to the
  25 public internet due to restrictive firewall rules, you
  26 need to set up local NTP servers and tell the NTP daemon to use
  27 them.
  28
  29 For systems using chrony:
  30 ^^^^^^^^^^^^^^^^^^^^^^^^^^
  31
  32 Specify which servers `chrony` should use in `/etc/chrony/chrony.conf`:
  33
  34 ----
  35 server ntp1.example.com iburst
  36 server ntp2.example.com iburst
  37 server ntp3.example.com iburst
  38 ----
  39
  40 Restart `chrony`:
  41
  42  # systemctl restart chronyd
  43
  44 Check the journal to confirm that the newly configured NTP servers are being
  45 used:
  46
  47  # journalctl --since -1h -u chrony
  48
  49 ----
  50 ...
  51 Aug 26 13:00:09 node1 systemd[1]: Started chrony, an NTP client/server.
  52 Aug 26 13:00:15 node1 chronyd[4873]: Selected source 10.0.0.1 (ntp1.example.com)
  53 Aug 26 13:00:15 node1 chronyd[4873]: System clock TAI offset set to 37 seconds
  54 ...
  55 ----
  56
  57 For systems using systemd-timesyncd:
  58 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  59
  60 Specify which servers `systemd-timesyncd` should use in
  61 `/etc/systemd/timesyncd.conf`:
  62
  63 ----
  64 [Time]
  65 NTP=ntp1.example.com ntp2.example.com ntp3.example.com ntp4.example.com
  66 ----
  67
  68 Then, restart the synchronization service (`systemctl restart
  69 systemd-timesyncd`), and verify that your newly configured NTP servers are in
  70 use by checking the journal (`journalctl --since -1h -u systemd-timesyncd`):
  71
  72 ----
  73 ...
  74 Oct 07 14:58:36 node1 systemd[1]: Stopping Network Time Synchronization...
  75 Oct 07 14:58:36 node1 systemd[1]: Starting Network Time Synchronization...
  76 Oct 07 14:58:36 node1 systemd[1]: Started Network Time Synchronization.
  77 Oct 07 14:58:36 node1 systemd-timesyncd[13514]: Using NTP server 10.0.0.1:123 (ntp1.example.com).
  78 Oct 07 14:58:36 node1 systemd-timesyncd[13514]: interval/delta/delay/jitter/drift 64s/-0.002s/0.020s/0.000s/-31ppm
  79 ...
  80 ----