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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
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8 | This file is part of systemd. |
9 | ||
10 | Copyright 2014 Kay Sievers | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
26 | <refentry id="systemd-timesyncd.service" conditional='ENABLE_TIMESYNCD'> | |
27 | ||
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28 | <refentryinfo> |
29 | <title>systemd-timesyncd.service</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>Developer</contrib> | |
35 | <firstname>Kay</firstname> | |
36 | <surname>Sievers</surname> | |
37 | <email>kay@vrfy.org</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>systemd-timesyncd.service</refentrytitle> | |
44 | <manvolnum>8</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>systemd-timesyncd.service</refname> | |
49 | <refname>systemd-timesyncd</refname> | |
50 | <refpurpose>Network Time Synchronization</refpurpose> | |
51 | </refnamediv> | |
52 | ||
53 | <refsynopsisdiv> | |
54 | <para><filename>systemd-timesyncd.service</filename></para> | |
12b42c76 | 55 | <para><filename>/usr/lib/systemd/systemd-timesyncd</filename></para> |
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56 | </refsynopsisdiv> |
57 | ||
58 | <refsect1> | |
59 | <title>Description</title> | |
60 | ||
61 | <para><filename>systemd-timesyncd</filename> is a system service | |
62 | that may be used to synchronize the local system clock with a | |
63 | remote Network Time Protocol server. It also saves the local time | |
64 | to disk every time the clock has been synchronized and uses this | |
65 | to possibly advance the system realtime clock on subsequent | |
66 | reboots to ensure it monotonically advances even if the system | |
67 | lacks a battery-buffered RTC chip.</para> | |
68 | ||
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69 | <para>The <filename>systemd-timesyncd</filename> service |
70 | specifically implements only SNTP. This minimalistic | |
71 | service will set the system clock for large offsets or | |
72 | slowly adjust it for smaller deltas. More complex use | |
73 | cases are not covered by <filename>systemd-timesyncd</filename>.</para> | |
74 | ||
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75 | <para>The NTP servers contacted are determined from the global |
76 | settings in | |
77 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
78 | the per-link static settings in <filename>.network</filename> | |
79 | files, and the per-link dynamic settings received over DHCP. See | |
80 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
81 | for more details.</para> | |
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82 | |
83 | <para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
84 | <command>set-ntp</command> command may be used to enable and | |
85 | start, or disable and stop this service.</para> | |
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86 | </refsect1> |
87 | ||
88 | <refsect1> | |
89 | <title>Files</title> | |
90 | ||
91 | <variablelist> | |
92 | <varlistentry> | |
53d133ea | 93 | <term><filename>/var/lib/systemd/timesync/clock</filename></term> |
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94 | |
95 | <listitem> | |
a8eaaee7 | 96 | <para>This file contains the timestamp of the last successful |
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97 | synchronization.</para> |
98 | </listitem> | |
99 | </varlistentry> | |
100 | </variablelist> | |
101 | </refsect1> | |
102 | ||
103 | <refsect1> | |
104 | <title>See Also</title> | |
105 | <para> | |
106 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
107 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
108 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
109 | <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
110 | <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
111 | <citerefentry><refentrytitle>localtime</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
112 | <citerefentry project='man-pages'><refentrytitle>hwclock</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
113 | </para> | |
114 | </refsect1> | |
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115 | |
116 | </refentry> |