1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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5 | %general-entities;
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6 | ]>
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7 |
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8 | <sect1 id="ch-scripts-clock">
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9 | <?dbhtml filename="clock.html"?>
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10 |
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11 | <title>Configuring the System Clock</title>
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12 |
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13 | <para>Procedures for setting the system clock differ between systemd and
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14 | System V, however the separate procedures do not conflict so both
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15 | procedures should be accomplished to allow switching between systems.</para>
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16 |
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17 | <sect2 id="ch-scripts-setclock">
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18 | <title>System V Clock Configuration</title>
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19 |
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20 | <indexterm zone="ch-scripts-setclock">
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21 | <primary sortas="d-setclock">setclock</primary>
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22 | <secondary>configuring</secondary></indexterm>
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23 |
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24 | <para>The <command>setclock</command> script reads the time from the hardware
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25 | clock, also known as the BIOS or the Complementary Metal Oxide Semiconductor
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26 | (CMOS) clock. If the hardware clock is set to UTC, this script will convert the
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27 | hardware clock's time to the local time using the
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28 | <filename>/etc/localtime</filename> file (which tells the
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29 | <command>hwclock</command> program which timezone the user is in). There is no
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30 | way to detect whether or not the hardware clock is set to UTC, so this
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31 | needs to be configured manually.</para>
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32 |
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33 | <para>The <command>setclock</command> is run via
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34 | <application>udev</application> when the kernel detects the hardware
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35 | capability upon boot. It can also be run manually with the stop parameter to
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36 | store the system time to the CMOS clock.</para>
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37 |
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38 | <para>If you cannot remember whether or not the hardware clock is set to UTC,
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39 | find out by running the <userinput>hwclock --localtime --show</userinput>
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40 | command. This will display what the current time is according to the hardware
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41 | clock. If this time matches whatever your watch says, then the hardware clock is
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42 | set to local time. If the output from <command>hwclock</command> is not local
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43 | time, chances are it is set to UTC time. Verify this by adding or subtracting
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44 | the proper amount of hours for the timezone to the time shown by
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45 | <command>hwclock</command>. For example, if you are currently in the MST
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46 | timezone, which is also known as GMT -0700, add seven hours to the local
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47 | time.</para>
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48 |
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49 | <para>Change the value of the <envar>UTC</envar> variable below
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50 | to a value of <parameter>0</parameter> (zero) if the hardware clock
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51 | is <emphasis>not</emphasis> set to UTC time.</para>
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52 |
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53 | <para>Create a new file <filename>/etc/sysconfig/clock</filename> by running
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54 | the following:</para>
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55 |
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56 | <screen><userinput>cat > /etc/sysconfig/clock << "EOF"
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57 | <literal># Begin /etc/sysconfig/clock
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58 |
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59 | UTC=1
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60 |
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61 | # Set this to any options you might need to give to hwclock,
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62 | # such as machine hardware clock type for Alphas.
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63 | CLOCKPARAMS=
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64 |
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65 | # End /etc/sysconfig/clock</literal>
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66 | EOF</userinput></screen>
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67 |
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68 | <para>A good hint explaining how to deal with time on LFS is available
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69 | at <ulink url="&hints-root;time.txt"/>. It explains issues such as
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70 | time zones, UTC, and the <envar>TZ</envar> environment variable.</para>
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71 |
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72 | <note><para>The CLOCKPARAMS and UTC paramaters may be alternatively set
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73 | in the <filename>/etc/sysconfig/rc.site</filename> file.</para></note>
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74 |
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75 | </sect2>
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76 |
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77 | <sect2 id="ch-scripts-systemd-clock">
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78 | <title>Systemd Clock Configuration</title>
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79 |
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80 | <indexterm zone="ch-scripts-clock">
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81 | <primary sortas="d-clock">clock</primary>
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82 | <secondary>configuring</secondary></indexterm>
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83 |
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84 | <para>This section discusses how to configure the
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85 | <command>systemd-timedated</command> system service, which configures
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86 | system clock and timezone.</para>
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87 |
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88 | <para><command>systemd-timedated</command> reads
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89 | <filename>/etc/adjtime</filename>, and depending on the contents of the file,
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90 | it sets the clock to either UTC or local time. Create the
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91 | <filename>/etc/adjtime</filename> file with the following contents <emphasis>if your
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92 | hardware clock is set to local time</emphasis>:</para>
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93 |
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94 | <screen role="nodump"><userinput>cat > /etc/adjtime << "EOF"
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95 | <literal>0.0 0 0.0
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96 | 0
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97 | LOCAL</literal>
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98 | EOF</userinput></screen>
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99 |
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100 | <para>If <filename>/etc/adjtime</filename> isn't present at first boot,
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101 | <command>systemd-timedated</command> will assume that hardware clock is
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102 | set to UTC and create the file using that setting.</para>
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103 |
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104 | <para>You can also use the <command>timedatectl</command> utility to tell
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105 | <command>systemd-timedated</command> if your hardware clock is set to
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106 | UTC or local time:</para>
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107 |
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108 | <screen role="nodump"><userinput>timedatectl set-local-rtc 1</userinput></screen>
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109 |
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110 | <para><command>timedatectl</command> can also be used to change system time and
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111 | time zone.</para>
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112 |
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113 | <para>To change your current system time, issue:</para>
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114 |
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115 | <screen role="nodump"><userinput>timedatectl set-time YYYY:MM:DD HH:MM:SS</userinput></screen>
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116 |
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117 | <para>Hardware clock will also be updated accordingly.</para>
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118 |
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119 | <para>To change your current time zone, issue:</para>
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120 |
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121 | <screen role="nodump"><userinput>timedatectl set-timezone TIMEZONE</userinput></screen>
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122 |
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123 | <para>You can get list of available time zones by running:</para>
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124 |
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125 | <screen role="nodump"><userinput>timedatectl list-timezones</userinput></screen>
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126 |
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127 | <note><para>Please note that <command>timedatectl</command> command can
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128 | be used only on a system booted with Systemd.</para></note>
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129 |
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130 | </sect2>
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131 |
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132 | </sect1>
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