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1 | <?xml version='1.0'?> <!--*-nxml-*--> | |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> | |
5 | ||
6 | <refentry id="systemd-timesyncd.service" conditional='ENABLE_TIMESYNCD'> | |
7 | ||
8 | <refentryinfo> | |
9 | <title>systemd-timesyncd.service</title> | |
10 | <productname>systemd</productname> | |
11 | </refentryinfo> | |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>systemd-timesyncd.service</refentrytitle> | |
15 | <manvolnum>8</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>systemd-timesyncd.service</refname> | |
20 | <refname>systemd-timesyncd</refname> | |
21 | <refpurpose>Network Time Synchronization</refpurpose> | |
22 | </refnamediv> | |
23 | ||
24 | <refsynopsisdiv> | |
25 | <para><filename>systemd-timesyncd.service</filename></para> | |
26 | <para><filename>/usr/lib/systemd/systemd-timesyncd</filename></para> | |
27 | </refsynopsisdiv> | |
28 | ||
29 | <refsect1> | |
30 | <title>Description</title> | |
31 | ||
32 | <para><filename>systemd-timesyncd</filename> is a system service | |
33 | that may be used to synchronize the local system clock with a | |
34 | remote Network Time Protocol server. It also saves the local time | |
35 | to disk every time the clock has been synchronized and uses this | |
36 | to possibly advance the system realtime clock on subsequent | |
37 | reboots to ensure it monotonically advances even if the system | |
38 | lacks a battery-buffered RTC chip.</para> | |
39 | ||
40 | <para>The <filename>systemd-timesyncd</filename> service | |
41 | specifically implements only SNTP. This minimalistic | |
42 | service will set the system clock for large offsets or | |
43 | slowly adjust it for smaller deltas. More complex use | |
44 | cases are not covered by <filename>systemd-timesyncd</filename>.</para> | |
45 | ||
46 | <para>The NTP servers contacted are determined from the global | |
47 | settings in | |
48 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
49 | the per-link static settings in <filename>.network</filename> | |
50 | files, and the per-link dynamic settings received over DHCP. See | |
51 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
52 | for more details.</para> | |
53 | ||
54 | <para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
55 | <command>set-ntp</command> command may be used to enable and | |
56 | start, or disable and stop this service.</para> | |
57 | ||
58 | <para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
59 | <command>timesync-status</command> or <command>show-timesync</command> command can be used to show the | |
60 | current status of this service.</para> | |
61 | </refsect1> | |
62 | ||
63 | <refsect1> | |
64 | <title>Files</title> | |
65 | ||
66 | <variablelist> | |
67 | <varlistentry> | |
68 | <term><filename>/var/lib/systemd/timesync/clock</filename></term> | |
69 | ||
70 | <listitem> | |
71 | <para>The modification time of this file indicates the timestamp of the last successful | |
72 | synchronization (or at least the systemd build date, in case synchronization was not | |
73 | possible).</para> | |
74 | </listitem> | |
75 | </varlistentry> | |
76 | ||
77 | <varlistentry> | |
78 | <term><filename>/run/systemd/timesync/synchronized</filename></term> | |
79 | ||
80 | <listitem> | |
81 | <para>A file that is touched on each successful synchronization, to assist | |
82 | <filename>systemd-time-wait-sync</filename> and other applications to detecting synchronization | |
83 | events.</para> | |
84 | </listitem> | |
85 | ||
86 | </varlistentry> | |
87 | </variablelist> | |
88 | </refsect1> | |
89 | ||
90 | <refsect1> | |
91 | <title>See Also</title> | |
92 | <para> | |
93 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
94 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
95 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
96 | <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
97 | <citerefentry><refentrytitle>systemd-time-wait-sync.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
98 | <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
99 | <citerefentry><refentrytitle>localtime</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
100 | <citerefentry project='man-pages'><refentrytitle>hwclock</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
101 | </para> | |
102 | </refsect1> | |
103 | ||
104 | </refentry> |