man/timesyncd.conf.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="timesyncd.conf" conditional='ENABLE_TIMESYNCD'
   7     xmlns:xi="http://www.w3.org/2001/XInclude">
   8   <refentryinfo>
   9     <title>timesyncd.conf</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>timesyncd.conf</refentrytitle>
  15     <manvolnum>5</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>timesyncd.conf</refname>
  20     <refname>timesyncd.conf.d</refname>
  21     <refpurpose>Network Time Synchronization configuration files</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><simplelist>
  26       <member><filename>/etc/systemd/timesyncd.conf</filename></member>
  27       <member><filename>/run/systemd/timesyncd.conf</filename></member>
  28       <member><filename>/usr/lib/systemd/timesyncd.conf</filename></member>
  29       <member><filename>/etc/systemd/timesyncd.conf.d/*.conf</filename></member>
  30       <member><filename>/run/systemd/timesyncd.conf.d/*.conf</filename></member>
  31       <member><filename>/usr/lib/systemd/timesyncd.conf.d/*.conf</filename></member>
  32     </simplelist></para>
  33   </refsynopsisdiv>
  34
  35   <refsect1>
  36     <title>Description</title>
  37
  38     <para>These configuration files control NTP network time synchronization. See
  39     <citerefentry><refentrytitle>systemd.syntax</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  40     for a general description of the syntax.</para>
  41   </refsect1>
  42
  43   <xi:include href="standard-conf.xml" xpointer="main-conf" />
  44
  45   <refsect1>
  46     <title>Options</title>
  47
  48     <para>The following settings are configured in the [Time] section:</para>
  49
  50     <variablelist class='network-directives'>
  51
  52       <varlistentry>
  53         <term><varname>NTP=</varname></term>
  54         <listitem><para>A space-separated list of NTP server host names or IP addresses. During runtime this
  55         list is combined with any per-interface NTP servers acquired from
  56         <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  57         <command>systemd-timesyncd</command> will contact all configured system or per-interface servers in
  58         turn, until one responds. When the empty string is assigned, the list of NTP servers is reset, and
  59         all prior assignments will have no effect. This setting defaults to an empty list.</para>
  60
  61         <xi:include href="version-info.xml" xpointer="v216"/></listitem>
  62       </varlistentry>
  63
  64       <varlistentry>
  65         <term><varname>FallbackNTP=</varname></term>
  66         <listitem><para>A space-separated list of NTP server host names or IP addresses to be used as the
  67         fallback NTP servers. Any per-interface NTP servers obtained from
  68         <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  69         take precedence over this setting, as do any servers set via <varname>NTP=</varname> above. This
  70         setting is hence only relevant if no other NTP server information is known. When the empty string is
  71         assigned, the list of NTP servers is reset, and all prior assignments will have no effect. If this
  72         option is not given, a compiled-in list of NTP servers is used.</para>
  73
  74         <xi:include href="version-info.xml" xpointer="v216"/></listitem>
  75       </varlistentry>
  76
  77       <varlistentry>
  78         <term><varname>RootDistanceMaxSec=</varname></term>
  79         <listitem><para>Maximum acceptable root distance, i.e. the maximum estimated time required for a
  80         packet to travel to the server we are connected to from the server with the reference clock. If
  81         the current server does not satisfy this limit, <command>systemd-timesyncd</command> will switch
  82         to a different server.</para>
  83
  84         <para>Takes a time span value. The default unit is seconds, but other units may be specified, see
  85         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
  86         Defaults to 5 seconds.</para>
  87
  88         <xi:include href="version-info.xml" xpointer="v236"/></listitem>
  89       </varlistentry>
  90
  91       <varlistentry>
  92         <term><varname>PollIntervalMinSec=</varname></term>
  93         <term><varname>PollIntervalMaxSec=</varname></term>
  94         <listitem><para>The minimum and maximum poll intervals for NTP messages. Polling starts at the
  95         minimum poll interval, and is adjusted within the specified limits in response to received packets.
  96         </para>
  97
  98         <para>Each setting takes a time span value. The default unit is seconds, but other units may be
  99         specified, see
 100         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 101         <varname>PollIntervalMinSec=</varname> defaults to 32 seconds and must not be smaller than
 102         16 seconds. <varname>PollIntervalMaxSec=</varname> defaults to 34 min 8 s (2048 seconds) and must be
 103         larger than <varname>PollIntervalMinSec=</varname>.</para>
 104
 105         <xi:include href="version-info.xml" xpointer="v236"/></listitem>
 106       </varlistentry>
 107
 108       <varlistentry>
 109         <term><varname>ConnectionRetrySec=</varname></term>
 110         <listitem><para>Specifies the minimum delay before subsequent attempts to contact a new NTP server
 111         are made.</para>
 112
 113         <para>Takes a time span value. The default unit is seconds, but other units may be specified, see
 114         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 115         Defaults to 30 seconds and must not be smaller than 1 second.</para>
 116
 117         <xi:include href="version-info.xml" xpointer="v248"/></listitem>
 118       </varlistentry>
 119
 120       <varlistentry>
 121         <term><varname>SaveIntervalSec=</varname></term>
 122         <listitem><para>The interval at which the current time is periodically saved to disk, in the absence
 123         of any recent synchronisation from an NTP server. This is especially useful for offline systems
 124         with no local RTC, as it will guarantee that the system clock remains roughly monotonic across
 125         reboots.</para>
 126
 127         <para>Takes a time interval value. The default unit is seconds, but other units may be specified, see
 128         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 129         Defaults to 60 seconds.</para>
 130
 131         <xi:include href="version-info.xml" xpointer="v250"/></listitem>
 132       </varlistentry>
 133
 134     </variablelist>
 135   </refsect1>
 136
 137   <refsect1>
 138       <title>See Also</title>
 139       <para><simplelist type="inline">
 140       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 141       <member><citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 142       <member><citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 143       </simplelist></para>
 144   </refsect1>
 145
 146 </refentry>