systemd/man/systemd-timedated.service.xml

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<refentry id="systemd-timedated.service" conditional='ENABLE_TIMEDATED'>

  <refentryinfo>
    <title>systemd-timedated.service</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-timedated.service</refentrytitle>
    <manvolnum>8</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd-timedated.service</refname>
    <refname>systemd-timedated</refname>
    <refpurpose>Time and date bus mechanism</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>systemd-timedated.service</filename></para>
    <para><filename>/usr/lib/systemd/systemd-timedated</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><filename>systemd-timedated</filename> is a system service
    that may be used as a mechanism to change the system clock and
    timezone, as well as to enable/disable network time synchronization.
    <filename>systemd-timedated</filename> is automatically activated
    on request and terminates itself when it is unused.</para>

    <para>The tool
    <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    is a command line client to this service.</para>

    <para>See the <ulink
    url="https://www.freedesktop.org/wiki/Software/systemd/timedated">
    developer documentation</ulink> for information about the APIs
    <filename>systemd-timedated</filename> provides.</para>
  </refsect1>

  <refsect1>
    <title>List of network time synchronization services</title>

    <para><command>systemd-timesyncd</command> will look for files with a <literal>.list</literal> extension
    in <filename>ntp-units.d/</filename> directories. Each file is parsed as a list of unit names, one per
    line. Empty lines and lines with comments (<literal>#</literal>) are ignored.  Files are read from
    <filename>/usr/lib/systemd/ntp-units.d/</filename> and the corresponding directories under
    <filename>/etc/</filename>, <filename>/run/</filename>, <filename>/usr/local/lib/</filename>. Files in
    <filename>/etc/</filename> override files with the same name in <filename>/run/</filename>,
    <filename>/usr/local/lib/</filename>, and <filename>/usr/lib/</filename>. Files in
    <filename>/run/</filename> override files with the same name under <filename>/usr/</filename>. Packages
    should install their configuration files in <filename>/usr/lib/</filename> (distribution packages) or
    <filename>/usr/local/lib/</filename> (local installs).</para>

    <example>
      <title><filename>ntp-units.d/</filename> entry for <command>systemd-timesyncd</command></title>
      <programlisting># /usr/lib/systemd/ntp-units.d/80-systemd-timesync.list
systemd-timesyncd.service
</programlisting>
    </example>

    <para>If the environment variable <varname>$SYSTEMD_TIMEDATED_NTP_SERVICES</varname> is set,
    <command>systemd-timesyncd</command> will parse the contents of that variable as a colon-separated list
    of unit names. When set, this variable overrides the file-based list described above.</para>

    <example>
      <title>An override that specifies that <command>chronyd</command> should be used if available</title>
      <programlisting>SYSTEMD_TIMEDATED_NTP_SERVICES=chronyd.service:systemd-timesyncd.service</programlisting>
    </example>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>localtime</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry project='man-pages'><refentrytitle>hwclock</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-timesyncd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>