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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="timesyncd.conf" conditional='ENABLE_TIMESYNCD'
+ xmlns:xi="http://www.w3.org/2001/XInclude">
+ <refentryinfo>
+ <title>timesyncd.conf</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>timesyncd.conf</refentrytitle>
+ <manvolnum>5</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>timesyncd.conf</refname>
+ <refname>timesyncd.conf.d</refname>
+ <refpurpose>Network Time Synchronization configuration files</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename>/etc/systemd/timesyncd.conf</filename></para>
+ <para><filename>/etc/systemd/timesyncd.conf.d/*.conf</filename></para>
+ <para><filename>/run/systemd/timesyncd.conf.d/*.conf</filename></para>
+ <para><filename>/usr/lib/systemd/timesyncd.conf.d/*.conf</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>These configuration files control NTP network time synchronization. See
+ <citerefentry><refentrytitle>systemd.syntax</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ for a general description of the syntax.</para>
+ </refsect1>
+
+ <xi:include href="standard-conf.xml" xpointer="main-conf" />
+
+ <refsect1>
+ <title>Options</title>
+
+ <para>The following settings are configured in the [Time] section:</para>
+
+ <variablelist class='network-directives'>
+
+ <varlistentry>
+ <term><varname>NTP=</varname></term>
+ <listitem><para>A space-separated list of NTP server host names or IP addresses. During runtime this
+ list is combined with any per-interface NTP servers acquired from
+ <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+ <command>systemd-timesyncd</command> will contact all configured system or per-interface servers in
+ turn, until one responds. When the empty string is assigned, the list of NTP servers is reset, and
+ all prior assignments will have no effect. This setting defaults to an empty list.</para>
+
+ <xi:include href="version-info.xml" xpointer="v216"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>FallbackNTP=</varname></term>
+ <listitem><para>A space-separated list of NTP server host names or IP addresses to be used as the
+ fallback NTP servers. Any per-interface NTP servers obtained from
+ <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ take precedence over this setting, as do any servers set via <varname>NTP=</varname> above. This
+ setting is hence only relevant if no other NTP server information is known. When the empty string is
+ assigned, the list of NTP servers is reset, and all prior assignments will have no effect. If this
+ option is not given, a compiled-in list of NTP servers is used.</para>
+
+ <xi:include href="version-info.xml" xpointer="v216"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>RootDistanceMaxSec=</varname></term>
+ <listitem><para>Maximum acceptable root distance, i.e. the maximum estimated time required for a
+ packet to travel to the server we are connected to from the server with the reference clock. If
+ the current server does not satisfy this limit, <command>systemd-timesyncd</command> will switch
+ to a different server.</para>
+
+ <para>Takes a time span value. The default unit is seconds, but other units may be specified, see
+ <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ Defaults to 5 seconds.</para>
+
+ <xi:include href="version-info.xml" xpointer="v236"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>PollIntervalMinSec=</varname></term>
+ <term><varname>PollIntervalMaxSec=</varname></term>
+ <listitem><para>The minimum and maximum poll intervals for NTP messages. Polling starts at the
+ minimum poll interval, and is adjusted within the specified limits in response to received packets.
+ </para>
+
+ <para>Each setting takes a time span value. The default unit is seconds, but other units may be
+ specified, see
+ <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ <varname>PollIntervalMinSec=</varname> defaults to 32 seconds and must not be smaller than
+ 16 seconds. <varname>PollIntervalMaxSec=</varname> defaults to 34 min 8 s (2048 seconds) and must be
+ larger than <varname>PollIntervalMinSec=</varname>.</para>
+
+ <xi:include href="version-info.xml" xpointer="v236"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>ConnectionRetrySec=</varname></term>
+ <listitem><para>Specifies the minimum delay before subsequent attempts to contact a new NTP server
+ are made.</para>
+
+ <para>Takes a time span value. The default unit is seconds, but other units may be specified, see
+ <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ Defaults to 30 seconds and must not be smaller than 1 second.</para>
+
+ <xi:include href="version-info.xml" xpointer="v248"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>SaveIntervalSec=</varname></term>
+ <listitem><para>The interval at which the current time is periodically saved to disk, in the absence
+ of any recent synchronisation from an NTP server. This is especially useful for offline systems
+ with no local RTC, as it will guarantee that the system clock remains roughly monotonic across
+ reboots.</para>
+
+ <para>Takes a time interval value. The default unit is seconds, but other units may be specified, see
+ <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ Defaults to 60 seconds.</para>
+
+ <xi:include href="version-info.xml" xpointer="v250"/></listitem>
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>