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