[1118b17] | 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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[afcfd74] | 8 | <sect1 id="ch-config-clock" revision="systemd">
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[1118b17] | 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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[afcfd74] | 13 | <indexterm zone="ch-config-clock">
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[1118b17] | 14 | <primary sortas="d-clock">clock</primary>
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| 15 | <secondary>configuring</secondary></indexterm>
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| 16 |
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| 17 | <para>This section discusses how to configure the
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| 18 | <command>systemd-timedated</command> system service, which configures
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[9e7475a] | 19 | the system clock and timezone.</para>
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[1118b17] | 20 |
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| 21 | <para>If you cannot remember whether or not the hardware clock is set to UTC,
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| 22 | find out by running the <userinput>hwclock --localtime --show</userinput>
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| 23 | command. This will display what the current time is according to the hardware
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| 24 | clock. If this time matches whatever your watch says, then the hardware clock is
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| 25 | set to local time. If the output from <command>hwclock</command> is not local
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| 26 | time, chances are it is set to UTC time. Verify this by adding or subtracting
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| 27 | the proper amount of hours for the timezone to the time shown by
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| 28 | <command>hwclock</command>. For example, if you are currently in the MST
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| 29 | timezone, which is also known as GMT -0700, add seven hours to the local
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| 30 | time.</para>
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| 31 |
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| 32 | <para><command>systemd-timedated</command> reads <filename>/etc/adjtime</filename>,
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[9e7475a] | 33 | and depending on the contents of the file, sets the clock to either UTC or
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[1118b17] | 34 | local time.</para>
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| 35 |
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| 36 | <para>Create the <filename>/etc/adjtime</filename> file with the following contents
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| 37 | if your hardware clock is set to local time:</para>
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| 38 |
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[8154126] | 39 | <screen><userinput>cat > /etc/adjtime << "EOF"
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[1118b17] | 40 | <literal>0.0 0 0.0
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| 41 | 0
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| 42 | LOCAL</literal>
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| 43 | EOF</userinput></screen>
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| 44 |
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| 45 | <para>If <filename>/etc/adjtime</filename> isn't present at first boot,
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| 46 | <command>systemd-timedated</command> will assume that hardware clock is
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| 47 | set to UTC and adjust the file according to that.</para>
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| 48 |
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| 49 | <para>You can also use the <command>timedatectl</command> utility to tell
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| 50 | <command>systemd-timedated</command> if your hardware clock is set to
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| 51 | UTC or local time:</para>
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| 52 |
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| 53 | <screen role="nodump"><userinput>timedatectl set-local-rtc 1</userinput></screen>
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| 54 |
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| 55 | <para><command>timedatectl</command> can also be used to change system time and
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| 56 | time zone.</para>
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| 57 |
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| 58 | <para>To change your current system time, issue:</para>
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| 59 |
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| 60 | <screen role="nodump"><userinput>timedatectl set-time YYYY-MM-DD HH:MM:SS</userinput></screen>
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| 61 |
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[9e7475a] | 62 | <para>The hardware clock will also be updated accordingly.</para>
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[1118b17] | 63 |
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| 64 | <para>To change your current time zone, issue:</para>
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| 65 |
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| 66 | <screen role="nodump"><userinput>timedatectl set-timezone TIMEZONE</userinput></screen>
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| 67 |
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[0d84af1] | 68 | <para>You can get a list of available time zones by running:</para>
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[1118b17] | 69 |
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| 70 | <screen role="nodump"><userinput>timedatectl list-timezones</userinput></screen>
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| 71 |
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[0d84af1] | 72 | <note><para>Please note that the <command>timedatectl</command> command can
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[1118b17] | 73 | be used only on a system booted with systemd.</para></note>
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| 74 |
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| 75 | <sect2>
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| 76 | <title>Network Time Synchronization</title>
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| 77 |
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| 78 | <para>Starting with version 213, systemd ships a daemon called
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| 79 | <command>systemd-timesyncd</command> which can be used to
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| 80 | synchronize the system time with remote NTP servers.</para>
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| 81 |
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| 82 | <para>The daemon is not intended as a replacement for the well
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| 83 | established NTP daemon, but as a client only implementation
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| 84 | of the SNTP protocol which can be used for less advanced
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| 85 | tasks and on resource limited systems.</para>
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| 86 |
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| 87 | <para>Starting with systemd version 216, the
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| 88 | <command>systemd-timesyncd</command> daemon is enabled by
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| 89 | default. If you want to disable it, issue the following
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| 90 | command:</para>
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| 91 |
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| 92 | <screen role="nodump"><userinput>systemctl disable systemd-timesyncd</userinput></screen>
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| 93 |
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| 94 | <para>The <filename>/etc/systemd/timesyncd.conf</filename> file
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| 95 | can be used to change the NTP servers that
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| 96 | <command>systemd-timesyncd</command> synchronizes with.</para>
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| 97 |
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| 98 | <para>Please note that when system clock is set to Local Time,
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| 99 | <command>systemd-timesyncd</command> won't update hardware
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| 100 | clock.</para>
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| 101 |
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| 102 | </sect2>
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| 103 |
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| 104 | </sect1>
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