mirror of
https://github.com/systemd/systemd.git
synced 2024-12-23 21:35:11 +03:00
115 lines
5.7 KiB
XML
115 lines
5.7 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
|
|
|
|
<refentry id="systemd-timesyncd.service" conditional='ENABLE_TIMESYNCD'>
|
|
|
|
<refentryinfo>
|
|
<title>systemd-timesyncd.service</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>systemd-timesyncd.service</refentrytitle>
|
|
<manvolnum>8</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>systemd-timesyncd.service</refname>
|
|
<refname>systemd-timesyncd</refname>
|
|
<refpurpose>Network Time Synchronization</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<para><filename>systemd-timesyncd.service</filename></para>
|
|
<para><filename>/usr/lib/systemd/systemd-timesyncd</filename></para>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para><filename>systemd-timesyncd</filename> is a system service that may be used to synchronize the
|
|
local system clock with a remote Network Time Protocol (NTP) server. It also saves the local time to disk
|
|
every time the clock has been synchronized and uses this to possibly advance the system realtime clock on
|
|
subsequent reboots to ensure it (roughly) monotonically advances even if the system lacks a
|
|
battery-buffered RTC chip.</para>
|
|
|
|
<para>The <filename>systemd-timesyncd</filename> service implements SNTP only. This minimalistic service
|
|
will step the system clock for large offsets or slowly adjust it for smaller deltas. Complex use cases
|
|
that require full NTP support (and where SNTP is not sufficient) are not covered by
|
|
<filename>systemd-timesyncd</filename>.</para>
|
|
|
|
<para>The NTP servers contacted are determined from the global settings in
|
|
<citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, the
|
|
per-link static settings in <filename>.network</filename> files, and the per-link dynamic settings
|
|
received over DHCP. See
|
|
<citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
|
|
further details.</para>
|
|
|
|
<para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
|
|
<command>set-ntp</command> command may be used to enable and start, or disable and stop this
|
|
service.</para>
|
|
|
|
<para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
|
|
<command>timesync-status</command> or <command>show-timesync</command> command can be used to show the
|
|
current status of this service.</para>
|
|
|
|
<para><filename>systemd-timesyncd</filename> initialization delays the start of units that are ordered
|
|
after <filename>time-set.target</filename> (see
|
|
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
|
|
details) until the local time has been updated from <filename>/var/lib/systemd/timesync/clock</filename>
|
|
(see below) in order to make it roughly monotonic. It does not delay other units until synchronization
|
|
with an accurate reference time sources has been reached. Use
|
|
<citerefentry><refentrytitle>systemd-time-wait-sync.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
to achieve that, which will delay start of units that are ordered after
|
|
<filename>time-sync.target</filename> until synchronization to an accurate reference clock is
|
|
reached.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Files</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>/var/lib/systemd/timesync/clock</filename></term>
|
|
|
|
<listitem>
|
|
<para>The modification time ("mtime") of this file is updated on each successful NTP synchronization
|
|
or after each <varname>SaveIntervalSec=</varname> time interval, as specified in
|
|
<citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
|
|
At the minimum, it will be set to the systemd build date. It is used to ensure that the system clock
|
|
remains roughly monotonic across reboots, in case no local RTC is available.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>/run/systemd/timesync/synchronized</filename></term>
|
|
|
|
<listitem>
|
|
<para>A file that is touched on each successful synchronization, to assist
|
|
<filename>systemd-time-wait-sync</filename> and other applications to detecting synchronization
|
|
with accurate reference clocks.</para>
|
|
</listitem>
|
|
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
<para>
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd-time-wait-sync.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</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>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|