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/4.2/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>/etc/systemd/timesyncd.conf.d/*.conf</filename></member>
  28       <member><filename>/run/systemd/timesyncd.conf.d/*.conf</filename></member>
  29       <member><filename>/usr/lib/systemd/timesyncd.conf.d/*.conf</filename></member>
  30     </simplelist></para>
  31   </refsynopsisdiv>
  32
  33   <refsect1>
  34     <title>Description</title>
  35
  36     <para>These configuration files control NTP network time synchronization. See
  37     <citerefentry><refentrytitle>systemd.syntax</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  38     for a general description of the syntax.</para>
  39   </refsect1>
  40
  41   <xi:include href="standard-conf.xml" xpointer="main-conf" />
  42
  43   <refsect1>
  44     <title>Options</title>
  45
  46     <para>The following settings are configured in the [Time] section:</para>
  47
  48     <variablelist class='network-directives'>
  49
  50       <varlistentry>
  51         <term><varname>NTP=</varname></term>
  52         <listitem><para>A space-separated list of NTP server host names or IP addresses. During runtime this
  53         list is combined with any per-interface NTP servers acquired from
  54         <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  55         <command>systemd-timesyncd</command> will contact all configured system or per-interface servers in
  56         turn, until one responds. When the empty string is assigned, the list of NTP servers is reset, and
  57         all prior assignments will have no effect. This setting defaults to an empty list.</para>
  58
  59         <xi:include href="version-info.xml" xpointer="v216"/></listitem>
  60       </varlistentry>
  61
  62       <varlistentry>
  63         <term><varname>FallbackNTP=</varname></term>
  64         <listitem><para>A space-separated list of NTP server host names or IP addresses to be used as the
  65         fallback NTP servers. Any per-interface NTP servers obtained from
  66         <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  67         take precedence over this setting, as do any servers set via <varname>NTP=</varname> above. This
  68         setting is hence only relevant if no other NTP server information is known. When the empty string is
  69         assigned, the list of NTP servers is reset, and all prior assignments will have no effect. If this
  70         option is not given, a compiled-in list of NTP servers is used.</para>
  71
  72         <xi:include href="version-info.xml" xpointer="v216"/></listitem>
  73       </varlistentry>
  74
  75       <varlistentry>
  76         <term><varname>RootDistanceMaxSec=</varname></term>
  77         <listitem><para>Maximum acceptable root distance, i.e. the maximum estimated time required for a
  78         packet to travel to the server we are connected to from the server with the reference clock. If
  79         the current server does not satisfy this limit, <command>systemd-timesyncd</command> will switch
  80         to a different server.</para>
  81
  82         <para>Takes a time span value. The default unit is seconds, but other units may be specified, see
  83         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
  84         Defaults to 5 seconds.</para>
  85
  86         <xi:include href="version-info.xml" xpointer="v236"/></listitem>
  87       </varlistentry>
  88
  89       <varlistentry>
  90         <term><varname>PollIntervalMinSec=</varname></term>
  91         <term><varname>PollIntervalMaxSec=</varname></term>
  92         <listitem><para>The minimum and maximum poll intervals for NTP messages. Polling starts at the
  93         minimum poll interval, and is adjusted within the specified limits in response to received packets.
  94         </para>
  95
  96         <para>Each setting takes a time span value. The default unit is seconds, but other units may be
  97         specified, see
  98         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
  99         <varname>PollIntervalMinSec=</varname> defaults to 32 seconds and must not be smaller than
 100         16 seconds. <varname>PollIntervalMaxSec=</varname> defaults to 34 min 8 s (2048 seconds) and must be
 101         larger than <varname>PollIntervalMinSec=</varname>.</para>
 102
 103         <xi:include href="version-info.xml" xpointer="v236"/></listitem>
 104       </varlistentry>
 105
 106       <varlistentry>
 107         <term><varname>ConnectionRetrySec=</varname></term>
 108         <listitem><para>Specifies the minimum delay before subsequent attempts to contact a new NTP server
 109         are made.</para>
 110
 111         <para>Takes a time span value. The default unit is seconds, but other units may be specified, see
 112         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 113         Defaults to 30 seconds and must not be smaller than 1 second.</para>
 114
 115         <xi:include href="version-info.xml" xpointer="v248"/></listitem>
 116       </varlistentry>
 117
 118       <varlistentry>
 119         <term><varname>SaveIntervalSec=</varname></term>
 120         <listitem><para>The interval at which the current time is periodically saved to disk, in the absence
 121         of any recent synchronisation from an NTP server. This is especially useful for offline systems
 122         with no local RTC, as it will guarantee that the system clock remains roughly monotonic across
 123         reboots.</para>
 124
 125         <para>Takes a time interval value. The default unit is seconds, but other units may be specified, see
 126         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 127         Defaults to 60 seconds.</para>
 128
 129         <xi:include href="version-info.xml" xpointer="v250"/></listitem>
 130       </varlistentry>
 131
 132     </variablelist>
 133   </refsect1>
 134
 135   <refsect1>
 136       <title>See Also</title>
 137       <para>
 138       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 139       <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 140       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 141       </para>
 142   </refsect1>
 143
 144 </refentry>