sysadmin: add section about NTP configuration

based on wiki article Configuration_of_Time_Syncronization_(NTP)

diff --git a/Makefile b/Makefile
index 67a2b7920c05755a94416f21f2eaff2266ef47c1..6125210b374f1866507f015dc1a220b88f70e4be 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -113,7 +113,8 @@ SYSADMIN_PARTS=                                     \
        system-software-updates                 \
        pve-disk-health-monitoring              \
        local-lvm                               \
-       local-zfs
+       local-zfs                               \
+       system-timesync
 
 SYSADMIN_SOURCES=                              \
        $(addsuffix .adoc, ${SYSADMIN_PARTS})   \

diff --git a/sysadmin.adoc b/sysadmin.adoc
index d48403ca9ccc3b2b867c764cdd517e06d5fab472..867176424d1e132c5809d8d096fc90c64e014c14 100644 (file)
--- a/sysadmin.adoc
+++ b/sysadmin.adoc
@@ -59,6 +59,8 @@ include::system-software-updates.adoc[]
 
 include::pve-network.adoc[]
 
+include::system-timesync.adoc[]
+
 include::pve-disk-health-monitoring.adoc[]
 
 include::local-lvm.adoc[]

diff --git a/system-timesync.adoc b/system-timesync.adoc
new file mode 100644 (file)
index 0000000..6e752a4
--- /dev/null
+++ b/system-timesync.adoc
@@ -0,0 +1,44 @@
+Time Synchronization
+--------------------
+include::attributes.txt[]
+
+The {pve} cluster stack itself relies heavily on the fact that all
+the nodes have precisely synchronized time. Some other components,
+like Ceph, also refuse to work properly if the local time on nodes is
+not in sync.
+
+Time synchronization between nodes can be achieved with the ``Network
+Time Protocol'' (`NTP`). {pve} uses `systemd-timesyncd` as NTP client
+by default, preconfigured to use a set of public servers. This setup
+works out of the box in most cases.
+
+
+Using Custom NTP Servers
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+In some cases, it might be desired to not use the default NTP
+servers. For example, if your {pve} 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]
+Servers=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
+...
+----