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 time, so this
needs to be manually configured.</para>

<para>If you cannot remember whether or not the hardware
clock is set to UTC time, find out by running
the <userinput>hwclock --localtime --show</userinput> command. This will tell
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 this
<command>hwclock</command> time. For example, if you live in the MST
timezone, which is also known as GMT -0700, add seven hours to the local
time. Then, account for Daylight Savings Time, which requires
subtracting an hour (or only add six in the first place) during the summer
months.</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>