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></listitem>
  56       </varlistentry>
  57
  58       <varlistentry>
  59         <term><varname>FallbackNTP=</varname></term>
  60         <listitem><para>A space-separated list of NTP server host names or IP addresses to be used as the
  61         fallback NTP servers. Any per-interface NTP servers obtained from
  62         <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  63         take precedence over this setting, as do any servers set via <varname>NTP=</varname> above. This
  64         setting is hence only relevant if no other NTP server information is known. When the empty string is
  65         assigned, the list of NTP servers is reset, and all prior assignments will have no effect. If this
  66         option is not given, a compiled-in list of NTP servers is used.</para></listitem>
  67       </varlistentry>
  68
  69       <varlistentry>
  70         <term><varname>RootDistanceMaxSec=</varname></term>
  71         <listitem><para>Maximum acceptable root distance, i.e. the maximum estimated time required for a
  72         packet to travel to the server we are connected to from the server with the reference clock. If
  73         the current server does not satisfy this limit, <command>systemd-timesyncd</command> will switch
  74         to a different server.</para>
  75
  76         <para>Takes a time span value. The default unit is seconds, but other units may be specified, see
  77         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
  78         Defaults to 5 seconds.</para></listitem>
  79       </varlistentry>
  80
  81       <varlistentry>
  82         <term><varname>PollIntervalMinSec=</varname></term>
  83         <term><varname>PollIntervalMaxSec=</varname></term>
  84         <listitem><para>The minimum and maximum poll intervals for NTP messages. Polling starts at the
  85         minimum poll interval, and is adjusted within the specified limits in response to received packets.
  86         </para>
  87
  88         <para>Each setting takes a time span value. The default unit is seconds, but other units may be
  89         specified, see
  90         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
  91         <varname>PollIntervalMinSec=</varname> defaults to 32 seconds and must not be smaller than
  92         16 seconds. <varname>PollIntervalMaxSec=</varname> defaults to 34 min 8 s (2048 seconds) and must be
  93         larger than <varname>PollIntervalMinSec=</varname>.</para></listitem>
  94       </varlistentry>
  95
  96       <varlistentry>
  97         <term><varname>ConnectionRetrySec=</varname></term>
  98         <listitem><para>Specifies the minimum delay before subsequent attempts to contact a new NTP server
  99         are made.</para>
 100
 101         <para>Takes a time span value. The default unit is seconds, but other units may be specified, see
 102         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 103         Defaults to 30 seconds and must not be smaller than 1 second.</para></listitem>
 104       </varlistentry>
 105
 106       <varlistentry>
 107         <term><varname>SaveIntervalSec=</varname></term>
 108         <listitem><para>The interval at which the current time is periodically saved to disk, in the absence
 109         of any recent synchronisation from an NTP server. This is especially useful for offline systems
 110         with no local RTC, as it will guarantee that the system clock remains roughly monotonic across
 111         reboots.</para>
 112
 113         <para>Takes a time interval 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 60 seconds.</para></listitem>
 116       </varlistentry>
 117
 118     </variablelist>
 119   </refsect1>
 120
 121   <refsect1>
 122       <title>See Also</title>
 123       <para>
 124       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 125       <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 126       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 127       </para>
 128   </refsect1>
 129
 130 </refentry>