man/systemd-timedated.service.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+ -->
   5
   6 <refentry id="systemd-timedated.service" conditional='ENABLE_TIMEDATED'>
   7
   8   <refentryinfo>
   9     <title>systemd-timedated.service</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>systemd-timedated.service</refentrytitle>
  15     <manvolnum>8</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>systemd-timedated.service</refname>
  20     <refname>systemd-timedated</refname>
  21     <refpurpose>Time and date bus mechanism</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><filename>systemd-timedated.service</filename></para>
  26     <para><filename>/usr/lib/systemd/systemd-timedated</filename></para>
  27   </refsynopsisdiv>
  28
  29   <refsect1>
  30     <title>Description</title>
  31
  32     <para><filename>systemd-timedated</filename> is a system service
  33     that may be used as a mechanism to change the system clock and
  34     timezone, as well as to enable/disable network time synchronization.
  35     <filename>systemd-timedated</filename> is automatically activated
  36     on request and terminates itself when it is unused.</para>
  37
  38     <para>The tool
  39     <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  40     is a command line client to this service.</para>
  41
  42     <para>See the <ulink
  43     url="https://www.freedesktop.org/wiki/Software/systemd/timedated">
  44     developer documentation</ulink> for information about the APIs
  45     <filename>systemd-timedated</filename> provides.</para>
  46   </refsect1>
  47
  48   <refsect1>
  49     <title>List of network time synchronization services</title>
  50
  51     <para><command>systemd-timesyncd</command> will look for files with a <literal>.list</literal> extension
  52     in <filename>ntp-units.d/</filename> directories. Each file is parsed as a list of unit names, one per
  53     line. Empty lines and lines with comments (<literal>#</literal>) are ignored.  Files are read from
  54     <filename>/usr/lib/systemd/ntp-units.d/</filename> and the corresponding directories under
  55     <filename>/etc/</filename>, <filename>/run/</filename>, <filename>/usr/local/lib/</filename>. Files in
  56     <filename>/etc/</filename> override files with the same name in <filename>/run/</filename>,
  57     <filename>/usr/local/lib/</filename>, and <filename>/usr/lib/</filename>. Files in
  58     <filename>/run/</filename> override files with the same name under <filename>/usr/</filename>. Packages
  59     should install their configuration files in <filename>/usr/lib/</filename> (distribution packages) or
  60     <filename>/usr/local/lib/</filename> (local installs).</para>
  61
  62     <example>
  63       <title><filename>ntp-units.d/</filename> entry for <command>systemd-timesyncd</command></title>
  64       <programlisting># /usr/lib/systemd/ntp-units.d/80-systemd-timesync.list
  65 systemd-timesyncd.service
  66 </programlisting>
  67     </example>
  68
  69     <para>If the environment variable <varname>$SYSTEMD_TIMEDATED_NTP_SERVICES</varname> is set,
  70     <command>systemd-timesyncd</command> will parse the contents of that variable as a colon-separated list
  71     of unit names. When set, this variable overrides the file-based list described above.</para>
  72
  73     <example>
  74       <title>An override that specifies that <command>chronyd</command> should be used if available</title>
  75       <programlisting>SYSTEMD_TIMEDATED_NTP_SERVICES=chronyd.service:systemd-timesyncd.service</programlisting>
  76     </example>
  77   </refsect1>
  78
  79   <refsect1>
  80     <title>See Also</title>
  81     <para>
  82       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  83       <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  84       <citerefentry><refentrytitle>localtime</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  85       <citerefentry project='man-pages'><refentrytitle>hwclock</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  86       <citerefentry><refentrytitle>systemd-timesyncd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  87     </para>
  88   </refsect1>
  89
  90 </refentry>