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