source: BOOK/system-config/common/setclock.xml@ 6748458

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<sect1 id="ch-config-setclock">
  <?dbhtml filename="setclock.html"?>

  <title>Configuring the setclock Script</title>

  <indexterm zone="ch-config-setclock">
    <primary sortas="d-setclock">setclock</primary>
  <secondary>configuring</secondary></indexterm>

  <para os="a">The <command>setclock</command> script reads the time from the
  hardware clock, also known as the BIOS or the Complementary Metal Oxide
  Semiconductor (CMOS) clock. If the hardware clock is set to UTC, this
  script will convert the hardware clock's time to the local time using
  the <filename>/etc/localtime</filename> file (which tells the
  <command>hwclock</command> program which timezone the user is in). There
  is no way to detect whether or not the hardware clock is set to UTC, so
  this needs to be configured manually.</para>

  <para os="b">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 os="c">Change the value of the <envar>UTC</envar> variable below
  to a value of <option>0</option> (zero) if the hardware clock
  is <emphasis>not</emphasis> set to UTC time.</para>

  <para os="d">Create a new file <filename>/etc/sysconfig/clock</filename> by running
  the following:</para>

<screen><userinput>cat &gt; /etc/sysconfig/clock &lt;&lt; "EOF"
<literal># Begin /etc/sysconfig/clock

UTC=1

# End /etc/sysconfig/clock</literal>
EOF</userinput></screen>

  <para os="e">A good hint explaining how to deal with time on CLFS is available
  at <ulink url="&hints-root;time.txt"/>. It explains issues such as
  time zones, UTC, and the <envar>TZ</envar> environment variable.</para>

</sect1>