man/systemd-timesyncd.service.xml

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  23
  24 <refentry id="systemd-timesyncd.service" conditional='ENABLE_TIMESYNCD'>
  25
  26   <refentryinfo>
  27     <title>systemd-timesyncd.service</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>Developer</contrib>
  33         <firstname>Kay</firstname>
  34         <surname>Sievers</surname>
  35         <email>kay@vrfy.org</email>
  36       </author>
  37     </authorgroup>
  38   </refentryinfo>
  39
  40   <refmeta>
  41     <refentrytitle>systemd-timesyncd.service</refentrytitle>
  42     <manvolnum>8</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>systemd-timesyncd.service</refname>
  47     <refname>systemd-timesyncd</refname>
  48     <refpurpose>Network Time Synchronization</refpurpose>
  49   </refnamediv>
  50
  51   <refsynopsisdiv>
  52     <para><filename>systemd-timesyncd.service</filename></para>
  53     <para><filename>/usr/lib/systemd/systemd-timesyncd</filename></para>
  54   </refsynopsisdiv>
  55
  56   <refsect1>
  57     <title>Description</title>
  58
  59     <para><filename>systemd-timesyncd</filename> is a system service
  60     that may be used to synchronize the local system clock with a
  61     remote Network Time Protocol server. It also saves the local time
  62     to disk every time the clock has been synchronized and uses this
  63     to possibly advance the system realtime clock on subsequent
  64     reboots to ensure it monotonically advances even if the system
  65     lacks a battery-buffered RTC chip.</para>
  66
  67     <para>The <filename>systemd-timesyncd</filename> service
  68     specifically implements only SNTP. This minimalistic
  69     service will set the system clock for large offsets or
  70     slowly adjust it for smaller deltas. More complex use
  71     cases are not covered by <filename>systemd-timesyncd</filename>.</para>
  72
  73     <para>The NTP servers contacted are determined from the global
  74     settings in
  75     <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  76     the per-link static settings in <filename>.network</filename>
  77     files, and the per-link dynamic settings received over DHCP. See
  78     <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  79     for more details.</para>
  80
  81     <para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
  82     <command>set-ntp</command> command may be used to enable and
  83     start, or disable and stop this service.</para>
  84   </refsect1>
  85
  86   <refsect1>
  87     <title>Files</title>
  88
  89     <variablelist>
  90       <varlistentry>
  91         <term><filename>/var/lib/systemd/clock</filename></term>
  92
  93         <listitem>
  94           <para>This file contains the timestamp of the last successful
  95           synchronization.</para>
  96         </listitem>
  97       </varlistentry>
  98     </variablelist>
  99   </refsect1>
 100
 101   <refsect1>
 102     <title>See Also</title>
 103     <para>
 104       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 105       <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 106       <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 107       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 108       <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 109       <citerefentry><refentrytitle>localtime</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 110       <citerefentry project='man-pages'><refentrytitle>hwclock</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 111     </para>
 112   </refsect1>
 113
 114 </refentry>