man/systemd-time-wait-sync.service.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2018 Peter A. Bigot
  11 -->
  12
  13 <refentry id="systemd-time-wait-sync.service" conditional='ENABLE_TIMESYNCD'>
  14
  15   <refentryinfo>
  16     <title>systemd-time-wait-sync.service</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Peter</firstname>
  23         <surname>Bigot</surname>
  24         <email>pab@pabigot.com</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>systemd-time-wait-sync.service</refentrytitle>
  31     <manvolnum>8</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>systemd-time-wait-sync.service</refname>
  36     <refname>systemd-time-wait-sync</refname>
  37     <refpurpose>Wait Until Kernel Time Synchronized</refpurpose>
  38   </refnamediv>
  39
  40   <refsynopsisdiv>
  41     <para><filename>systemd-time-wait-sync.service</filename></para>
  42     <para><filename>/usr/lib/systemd/systemd-time-wait-sync</filename></para>
  43   </refsynopsisdiv>
  44
  45   <refsect1>
  46     <title>Description</title>
  47
  48     <para><filename>systemd-time-wait-sync</filename> is a system service that delays the start of units that depend on
  49     <filename>time-sync.target</filename> until <filename>systemd-timesyncd.service</filename> or something else has
  50     set the system time and marked it as synchronized.  Reaching this state generally requires synchronization with an
  51     external source, such as an NTP server.</para>
  52
  53     <para>When this unit is not enabled the <filename>time-sync.target</filename> synchronization point may be reached
  54     as soon as the system time is advanced by <filename>systemd-timesyncd.service</filename> to the time stored at the
  55     last shutdown.  That time may not meet the expectations of dependent services that require an accurate
  56     clock.</para>
  57
  58   </refsect1>
  59
  60   <refsect1>
  61     <title>Notes</title>
  62
  63     <para>This service works correctly with a time synchronization service like
  64     <filename>systemd-timesyncd.service</filename> that uses the same protocol as NTP to set the time from a
  65     synchronized source.  When used with time synchronization services that follow a different protocol the event of
  66     setting synchronized time may not be detected in which case this service will not complete.</para>
  67   </refsect1>
  68
  69   <refsect1>
  70     <title>See Also</title>
  71     <para>
  72       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  73       <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
  74       <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  75     </para>
  76   </refsect1>
  77
  78 </refentry>