lfs-book/chapter07/clock.xml

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<sect1 id="ch-scripts-clock">
  <?dbhtml filename="clock.html"?>

  <title>Configuring the system clock</title>

  <indexterm zone="ch-scripts-clock">
    <primary sortas="d-clock">clock</primary>
  <secondary>configuring</secondary></indexterm>

  <para>This section discusses how to configure the
  <command>systemd-timedated</command> system service, which configures
  system clock and timezone.</para>

  <para>Systemd provides a <command>timedatectl</command> utility which is
  used to communicate with <command>systemd-timedated</command>. It can be used
  to set the system clock in local time or UTC time, depending on the hardware
  clock setting. By default, <command>systemd-timedated</command> will assume
  that clock is set to UTC time.</para>

  <para>If you cannot remember whether or not the hardware clock is set to UTC,
  find out by running the <userinput>hwclock --localtime --show</userinput>
  command. This will display what the current time is according to the hardware
  clock. If this time matches whatever your watch says, then the hardware clock is
  set to local time. If the output from <command>hwclock</command> is not local
  time, chances are it is set to UTC time. Verify this by adding or subtracting
  the proper amount of hours for the timezone to the time shown by
  <command>hwclock</command>. For example, if you are currently in the MST
  timezone, which is also known as GMT -0700, add seven hours to the local
  time.</para>

  <para>If your clock is set to local time, tell <command>systemd-timedated</command>
  about it by running the following command:</para>

<screen role="nodump"><userinput>timedatectl set-local-rtc 1</userinput></screen>

  <para><command>timedatectl</command> can also be used to change system time and
  time zone.</para>

  <para>To change your current system time, issue:</para>

<screen role="nodump"><userinput>timedatectl set-time YYYY:MM:DD HH:MM:SS</userinput></screen>

  <para>Hardware clock will also be updated accordingly.</para>

  <para>To change your current time zone, issue:</para>

<screen role="nodump"><userinput>timedatectl set-timezone TIMEZONE</userinput></screen>

  <para>You can get list of available time zones by running:</para>

<screen role="nodump"><userinput>timedatectl list-timezones</userinput></screen>

  <note><para>Please note that <command>timedatectl</command> command can
  be used only on a system booted with Systemd.</para></note>

</sect1>