time-wait-sync: use watchfile to coordinate with timesyncd

[thirdparty/systemd.git] / man / systemd-time-wait-sync.service.xml

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  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  SPDX-License-Identifier: LGPL-2.1+

  This file is part of systemd.

  Copyright 2018 Peter A. Bigot
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<refentry id="systemd-time-wait-sync.service" conditional='ENABLE_TIMESYNCD'>

  <refentryinfo>
    <title>systemd-time-wait-sync.service</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Peter</firstname>
        <surname>Bigot</surname>
        <email>pab@pabigot.com</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-time-wait-sync.service</refentrytitle>
    <manvolnum>8</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd-time-wait-sync.service</refname>
    <refname>systemd-time-wait-sync</refname>
    <refpurpose>Wait Until Kernel Time Synchronized</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>systemd-time-wait-sync.service</filename></para>
    <para><filename>/usr/lib/systemd/systemd-time-wait-sync</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><filename>systemd-time-wait-sync</filename> is a system service that delays the start of units that depend on
    <filename>time-sync.target</filename> until the system time has been synchronized with an accurate time source by
    <filename>systemd-timesyncd.service</filename>.</para>

    <para><filename>systemd-timesyncd.service</filename> notifies on successful synchronization.
    <filename>systemd-time-wait-sync</filename> also tries to detect when the kernel marks the time as synchronized,
    but this detection is not reliable and is intended only as a fallback for other servies that can be used to
    synchronize time (e.g., ntpd, chronyd).</para>

  </refsect1>

  <refsect1>
    <title>Files</title>

    <variablelist>
      <varlistentry>
        <term><filename>/run/systemd/timesync/synchronized</filename></term>

        <listitem>
          <para>The presence of this file indicates to this service that the system clock has been synchronized.</para>
        </listitem>

      </varlistentry>
    </variablelist>

  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
    </para>
  </refsect1>

</refentry>