lfs-book/chapter07/setclock.xml

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<sect1 id="ch-scripts-setclock">
<title>Configuring the setclock Script</title>
<?dbhtml filename="setclock.html"?>

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

<para>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>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>Change the value of the <envar>UTC</envar> variable below
to a value of <parameter>0</parameter> (zero) if the hardware clock
is <emphasis>not</emphasis> set to UTC time.</para>

<para>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>A good hint explaining how to deal with time on LFS 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>