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systemd-stable/man/systemd-time-wait-sync.service.xml
Peter A. Bigot 2dd79846dd time-wait-sync: use watchfile to coordinate with timesyncd
Systems that have an accurate real-time clock may have an initial
unsynchronized time that is close enough to the synchronized time that
the final adjustment doesn't trigger a waking "clock set" event.  Have
timesyncd touch a file in its runtime directory as a secondary signal
for synchronization.  Continue to support the timerfd-based trigger as a
sufficient condition when the watchfile is not present.

Closes issue #8683
2018-04-14 09:52:40 -05:00

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XML

<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"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
-->
<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>