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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 | ||
96b2fb93 | 8 | Copyright © 2014 Kay Sievers |
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9 | --> |
10 | ||
11 | <refentry id="systemd-timesyncd.service" conditional='ENABLE_TIMESYNCD'> | |
12 | ||
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13 | <refentryinfo> |
14 | <title>systemd-timesyncd.service</title> | |
15 | <productname>systemd</productname> | |
16 | ||
17 | <authorgroup> | |
18 | <author> | |
19 | <contrib>Developer</contrib> | |
20 | <firstname>Kay</firstname> | |
21 | <surname>Sievers</surname> | |
22 | <email>kay@vrfy.org</email> | |
23 | </author> | |
24 | </authorgroup> | |
25 | </refentryinfo> | |
26 | ||
27 | <refmeta> | |
28 | <refentrytitle>systemd-timesyncd.service</refentrytitle> | |
29 | <manvolnum>8</manvolnum> | |
30 | </refmeta> | |
31 | ||
32 | <refnamediv> | |
33 | <refname>systemd-timesyncd.service</refname> | |
34 | <refname>systemd-timesyncd</refname> | |
35 | <refpurpose>Network Time Synchronization</refpurpose> | |
36 | </refnamediv> | |
37 | ||
38 | <refsynopsisdiv> | |
39 | <para><filename>systemd-timesyncd.service</filename></para> | |
12b42c76 | 40 | <para><filename>/usr/lib/systemd/systemd-timesyncd</filename></para> |
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41 | </refsynopsisdiv> |
42 | ||
43 | <refsect1> | |
44 | <title>Description</title> | |
45 | ||
46 | <para><filename>systemd-timesyncd</filename> is a system service | |
47 | that may be used to synchronize the local system clock with a | |
48 | remote Network Time Protocol server. It also saves the local time | |
49 | to disk every time the clock has been synchronized and uses this | |
50 | to possibly advance the system realtime clock on subsequent | |
51 | reboots to ensure it monotonically advances even if the system | |
52 | lacks a battery-buffered RTC chip.</para> | |
53 | ||
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54 | <para>The <filename>systemd-timesyncd</filename> service |
55 | specifically implements only SNTP. This minimalistic | |
56 | service will set the system clock for large offsets or | |
57 | slowly adjust it for smaller deltas. More complex use | |
58 | cases are not covered by <filename>systemd-timesyncd</filename>.</para> | |
59 | ||
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60 | <para>The NTP servers contacted are determined from the global |
61 | settings in | |
62 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
63 | the per-link static settings in <filename>.network</filename> | |
64 | files, and the per-link dynamic settings received over DHCP. See | |
65 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
66 | for more details.</para> | |
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67 | |
68 | <para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
69 | <command>set-ntp</command> command may be used to enable and | |
70 | start, or disable and stop this service.</para> | |
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71 | |
72 | <para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
73 | <command>timesync-status</command> or <command>show-timesync</command> command can be used to show the | |
74 | current status of this service.</para> | |
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75 | </refsect1> |
76 | ||
77 | <refsect1> | |
78 | <title>Files</title> | |
79 | ||
80 | <variablelist> | |
81 | <varlistentry> | |
53d133ea | 82 | <term><filename>/var/lib/systemd/timesync/clock</filename></term> |
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83 | |
84 | <listitem> | |
2dd79846 | 85 | <para>The modification time of this file indicates the timestamp of the last successful |
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86 | synchronization (or at least the systemd build date, in case synchronization was not |
87 | possible).</para> | |
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88 | </listitem> |
89 | </varlistentry> | |
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90 | |
91 | <varlistentry> | |
92 | <term><filename>/run/systemd/timesync/synchronized</filename></term> | |
93 | ||
94 | <listitem> | |
95 | <para>A file that is touched on each successful synchronization, to assist | |
96 | <filename>systemd-time-wait-sync</filename> and other applications to detecting synchronization | |
97 | events.</para> | |
98 | </listitem> | |
99 | ||
100 | </varlistentry> | |
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101 | </variablelist> |
102 | </refsect1> | |
103 | ||
104 | <refsect1> | |
105 | <title>See Also</title> | |
106 | <para> | |
107 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
108 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
109 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
110 | <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
2dd79846 | 111 | <citerefentry><refentrytitle>systemd-time-wait-sync.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
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112 | <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
113 | <citerefentry><refentrytitle>localtime</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
114 | <citerefentry project='man-pages'><refentrytitle>hwclock</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
115 | </para> | |
116 | </refsect1> | |
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117 | |
118 | </refentry> |