1 | <?xml version="1.0" encoding="ISO-8859-1"?>
|
---|
2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
---|
3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
|
---|
4 | <!ENTITY % general-entities SYSTEM "../general.ent">
|
---|
5 | %general-entities;
|
---|
6 | ]>
|
---|
7 |
|
---|
8 | <sect1 id="ch-config-clock" revision="systemd">
|
---|
9 | <?dbhtml filename="clock.html"?>
|
---|
10 |
|
---|
11 | <title>Configuring the system clock</title>
|
---|
12 |
|
---|
13 | <indexterm zone="ch-config-clock">
|
---|
14 | <primary sortas="d-clock">clock</primary>
|
---|
15 | <secondary>configuring</secondary></indexterm>
|
---|
16 |
|
---|
17 | <para>This section discusses how to configure the
|
---|
18 | <command>systemd-timedated</command> system service, which configures
|
---|
19 | the system clock and timezone.</para>
|
---|
20 |
|
---|
21 | <para>If you cannot remember whether or not the hardware clock is set to UTC,
|
---|
22 | find out by running the <userinput>hwclock --localtime --show</userinput>
|
---|
23 | command. This will display what the current time is according to the hardware
|
---|
24 | clock. If this time matches whatever your watch says, then the hardware clock is
|
---|
25 | set to local time. If the output from <command>hwclock</command> is not local
|
---|
26 | time, chances are it is set to UTC time. Verify this by adding or subtracting
|
---|
27 | the proper amount of hours for the timezone to the time shown by
|
---|
28 | <command>hwclock</command>. For example, if you are currently in the MST
|
---|
29 | timezone, which is also known as GMT -0700, add seven hours to the local
|
---|
30 | time.</para>
|
---|
31 |
|
---|
32 | <para><command>systemd-timedated</command> reads <filename>/etc/adjtime</filename>,
|
---|
33 | and depending on the contents of the file, sets the clock to either UTC or
|
---|
34 | local time.</para>
|
---|
35 |
|
---|
36 | <para>Create the <filename>/etc/adjtime</filename> file with the following contents
|
---|
37 | if your hardware clock is set to local time:</para>
|
---|
38 |
|
---|
39 | <screen><userinput>cat > /etc/adjtime << "EOF"
|
---|
40 | <literal>0.0 0 0.0
|
---|
41 | 0
|
---|
42 | LOCAL</literal>
|
---|
43 | EOF</userinput></screen>
|
---|
44 |
|
---|
45 | <para>If <filename>/etc/adjtime</filename> isn't present at first boot,
|
---|
46 | <command>systemd-timedated</command> will assume that hardware clock is
|
---|
47 | set to UTC and adjust the file according to that.</para>
|
---|
48 |
|
---|
49 | <para>You can also use the <command>timedatectl</command> utility to tell
|
---|
50 | <command>systemd-timedated</command> if your hardware clock is set to
|
---|
51 | UTC or local time:</para>
|
---|
52 |
|
---|
53 | <screen role="nodump"><userinput>timedatectl set-local-rtc 1</userinput></screen>
|
---|
54 |
|
---|
55 | <para><command>timedatectl</command> can also be used to change system time and
|
---|
56 | time zone.</para>
|
---|
57 |
|
---|
58 | <para>To change your current system time, issue:</para>
|
---|
59 |
|
---|
60 | <screen role="nodump"><userinput>timedatectl set-time YYYY-MM-DD HH:MM:SS</userinput></screen>
|
---|
61 |
|
---|
62 | <para>The hardware clock will also be updated accordingly.</para>
|
---|
63 |
|
---|
64 | <para>To change your current time zone, issue:</para>
|
---|
65 |
|
---|
66 | <screen role="nodump"><userinput>timedatectl set-timezone TIMEZONE</userinput></screen>
|
---|
67 |
|
---|
68 | <para>You can get a list of available time zones by running:</para>
|
---|
69 |
|
---|
70 | <screen role="nodump"><userinput>timedatectl list-timezones</userinput></screen>
|
---|
71 |
|
---|
72 | <note><para>Please note that the <command>timedatectl</command> command can
|
---|
73 | be used only on a system booted with systemd.</para></note>
|
---|
74 |
|
---|
75 | <sect2>
|
---|
76 | <title>Network Time Synchronization</title>
|
---|
77 |
|
---|
78 | <para>Starting with version 213, systemd ships a daemon called
|
---|
79 | <command>systemd-timesyncd</command> which can be used to
|
---|
80 | synchronize the system time with remote NTP servers.</para>
|
---|
81 |
|
---|
82 | <para>The daemon is not intended as a replacement for the well
|
---|
83 | established NTP daemon, but as a client only implementation
|
---|
84 | of the SNTP protocol which can be used for less advanced
|
---|
85 | tasks and on resource limited systems.</para>
|
---|
86 |
|
---|
87 | <para>Starting with systemd version 216, the
|
---|
88 | <command>systemd-timesyncd</command> daemon is enabled by
|
---|
89 | default. If you want to disable it, issue the following
|
---|
90 | command:</para>
|
---|
91 |
|
---|
92 | <screen role="nodump"><userinput>systemctl disable systemd-timesyncd</userinput></screen>
|
---|
93 |
|
---|
94 | <para>The <filename>/etc/systemd/timesyncd.conf</filename> file
|
---|
95 | can be used to change the NTP servers that
|
---|
96 | <command>systemd-timesyncd</command> synchronizes with.</para>
|
---|
97 |
|
---|
98 | <para>Please note that when system clock is set to Local Time,
|
---|
99 | <command>systemd-timesyncd</command> won't update hardware
|
---|
100 | clock.</para>
|
---|
101 |
|
---|
102 | </sect2>
|
---|
103 |
|
---|
104 | </sect1>
|
---|