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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 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
9 | <refentry id="systemd-timesyncd.service" conditional='ENABLE_TIMESYNCD'> | |
10 | ||
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11 | <refentryinfo> |
12 | <title>systemd-timesyncd.service</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>systemd-timesyncd.service</refentrytitle> | |
18 | <manvolnum>8</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>systemd-timesyncd.service</refname> | |
23 | <refname>systemd-timesyncd</refname> | |
24 | <refpurpose>Network Time Synchronization</refpurpose> | |
25 | </refnamediv> | |
26 | ||
27 | <refsynopsisdiv> | |
28 | <para><filename>systemd-timesyncd.service</filename></para> | |
12b42c76 | 29 | <para><filename>/usr/lib/systemd/systemd-timesyncd</filename></para> |
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30 | </refsynopsisdiv> |
31 | ||
32 | <refsect1> | |
33 | <title>Description</title> | |
34 | ||
35 | <para><filename>systemd-timesyncd</filename> is a system service | |
36 | that may be used to synchronize the local system clock with a | |
37 | remote Network Time Protocol server. It also saves the local time | |
38 | to disk every time the clock has been synchronized and uses this | |
39 | to possibly advance the system realtime clock on subsequent | |
40 | reboots to ensure it monotonically advances even if the system | |
41 | lacks a battery-buffered RTC chip.</para> | |
42 | ||
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43 | <para>The <filename>systemd-timesyncd</filename> service |
44 | specifically implements only SNTP. This minimalistic | |
45 | service will set the system clock for large offsets or | |
46 | slowly adjust it for smaller deltas. More complex use | |
47 | cases are not covered by <filename>systemd-timesyncd</filename>.</para> | |
48 | ||
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49 | <para>The NTP servers contacted are determined from the global |
50 | settings in | |
51 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
52 | the per-link static settings in <filename>.network</filename> | |
53 | files, and the per-link dynamic settings received over DHCP. See | |
54 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
55 | for more details.</para> | |
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56 | |
57 | <para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
58 | <command>set-ntp</command> command may be used to enable and | |
59 | start, or disable and stop this service.</para> | |
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60 | |
61 | <para><citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
62 | <command>timesync-status</command> or <command>show-timesync</command> command can be used to show the | |
63 | current status of this service.</para> | |
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64 | </refsect1> |
65 | ||
66 | <refsect1> | |
67 | <title>Files</title> | |
68 | ||
69 | <variablelist> | |
70 | <varlistentry> | |
53d133ea | 71 | <term><filename>/var/lib/systemd/timesync/clock</filename></term> |
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72 | |
73 | <listitem> | |
2dd79846 | 74 | <para>The modification time of this file indicates the timestamp of the last successful |
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75 | synchronization (or at least the systemd build date, in case synchronization was not |
76 | possible).</para> | |
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77 | </listitem> |
78 | </varlistentry> | |
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79 | |
80 | <varlistentry> | |
81 | <term><filename>/run/systemd/timesync/synchronized</filename></term> | |
82 | ||
83 | <listitem> | |
84 | <para>A file that is touched on each successful synchronization, to assist | |
85 | <filename>systemd-time-wait-sync</filename> and other applications to detecting synchronization | |
86 | events.</para> | |
87 | </listitem> | |
88 | ||
89 | </varlistentry> | |
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90 | </variablelist> |
91 | </refsect1> | |
92 | ||
93 | <refsect1> | |
94 | <title>See Also</title> | |
95 | <para> | |
96 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
97 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
98 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
99 | <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
2dd79846 | 100 | <citerefentry><refentrytitle>systemd-time-wait-sync.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
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101 | <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
102 | <citerefentry><refentrytitle>localtime</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
103 | <citerefentry project='man-pages'><refentrytitle>hwclock</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
104 | </para> | |
105 | </refsect1> | |
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106 | |
107 | </refentry> |