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

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  10   Copyright 2018 Peter A. Bigot
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  25
  26 <refentry id="systemd-time-wait-sync.service" conditional='ENABLE_TIMESYNCD'>
  27
  28   <refentryinfo>
  29     <title>systemd-time-wait-sync.service</title>
  30     <productname>systemd</productname>
  31
  32     <authorgroup>
  33       <author>
  34         <contrib>Developer</contrib>
  35         <firstname>Peter</firstname>
  36         <surname>Bigot</surname>
  37         <email>pab@pabigot.com</email>
  38       </author>
  39     </authorgroup>
  40   </refentryinfo>
  41
  42   <refmeta>
  43     <refentrytitle>systemd-time-wait-sync.service</refentrytitle>
  44     <manvolnum>8</manvolnum>
  45   </refmeta>
  46
  47   <refnamediv>
  48     <refname>systemd-time-wait-sync.service</refname>
  49     <refname>systemd-time-wait-sync</refname>
  50     <refpurpose>Wait Until Kernel Time Synchronized</refpurpose>
  51   </refnamediv>
  52
  53   <refsynopsisdiv>
  54     <para><filename>systemd-time-wait-sync.service</filename></para>
  55     <para><filename>/usr/lib/systemd/systemd-time-wait-sync</filename></para>
  56   </refsynopsisdiv>
  57
  58   <refsect1>
  59     <title>Description</title>
  60
  61     <para><filename>systemd-time-wait-sync</filename> is a system service that delays the start of units that depend on
  62     <filename>time-sync.target</filename> until <filename>systemd-timesyncd.service</filename> or something else has
  63     set the system time and marked it as synchronized.  Reaching this state generally requires synchronization with an
  64     external source, such as an NTP server.</para>
  65
  66     <para>When this unit is not enabled the <filename>time-sync.target</filename> synchronization point may be reached
  67     as soon as the system time is advanced by <filename>systemd-timesyncd.service</filename> to the time stored at the
  68     last shutdown.  That time may not meet the expectations of dependent services that require an accurate
  69     clock.</para>
  70
  71   </refsect1>
  72
  73   <refsect1>
  74     <title>Notes</title>
  75
  76     <para>This service works correctly with a time synchronization service like
  77     <filename>systemd-timesyncd.service</filename> that uses the same protocol as NTP to set the time from a
  78     synchronized source.  When used with time synchronization services that follow a different protocol the event of
  79     setting synchronized time may not be detected in which case this service will not complete.</para>
  80   </refsect1>
  81
  82   <refsect1>
  83     <title>See Also</title>
  84     <para>
  85       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  86       <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
  87       <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  88     </para>
  89   </refsect1>
  90
  91 </refentry>