source: BOOK/system-config/common/clock.xml @ 0d36d0a

clfs-3.0.0-systemdsystemd
Last change on this file since 0d36d0a was 0d36d0a, checked in by Chris Staub <chris@…>, 10 years ago

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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">
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  system clock and timezone.</para>
20
21  <para>Systemd provides a <command>timedatectl</command> utility which is
22  used to communicate with <command>systemd-timedated</command>. It can be used
23  to set the system clock in local time or UTC time, depending on the hardware
24  clock setting. By default, <command>systemd-timedated</command> will assume
25  that clock is set to UTC time.</para>
26
27  <para>If you cannot remember whether or not the hardware clock is set to UTC,
28  find out by running the <userinput>hwclock --localtime --show</userinput>
29  command. This will display what the current time is according to the hardware
30  clock. If this time matches whatever your watch says, then the hardware clock is
31  set to local time. If the output from <command>hwclock</command> is not local
32  time, chances are it is set to UTC time. Verify this by adding or subtracting
33  the proper amount of hours for the timezone to the time shown by
34  <command>hwclock</command>. For example, if you are currently in the MST
35  timezone, which is also known as GMT -0700, add seven hours to the local
36  time.</para>
37
38  <para><command>systemd-timedated</command> reads
39  <filename>/etc/adjtime</filename>, and depending on the contents of the file,
40  it sets the clock to either UTC or local time.</para>
41
42 <para>Create the <filename>/etc/adjtime</filename> file with the following
43 contents if your hardware clock is set to local time:</para>
44
45<screen role="nodump"><userinput>cat &gt; /etc/adjtime &lt;&lt; "EOF"
46<literal>0.0 0 0.0
470
48LOCAL</literal>
49EOF</userinput></screen>
50
51 <para>If <filename>/etc/adjtime</filename> isn't present at first boot,
52 <command>systemd-timedated</command> will assume that hardware clock is
53 set to UTC and adjust the file according to that.</para>
54
55  <para>If your clock is set to local time, tell
56  <command>systemd-timedated</command> about it by running the following
57  command:</para>
58
59<screen role="nodump"><userinput>timedatectl set-local-rtc 1</userinput></screen>
60
61  <para><command>timedatectl</command> can also be used to change system time and
62  time zone.</para>
63
64  <para>To change your current system time, issue:</para>
65
66<screen role="nodump"><userinput>timedatectl set-time YYYY:MM:DD HH:MM:SS</userinput></screen>
67
68  <para>Hardware clock will also be updated accordingly.</para>
69
70  <para>To change your current time zone, issue:</para>
71
72<screen role="nodump"><userinput>timedatectl set-timezone TIMEZONE</userinput></screen>
73
74  <para>You can get list of available time zones by running:</para>
75
76<screen role="nodump"><userinput>timedatectl list-timezones</userinput></screen>
77
78  <note><para>Please note that <command>timedatectl</command> command can
79  be used only on a system booted with systemd.</para></note>
80
81</sect1>
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