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<H1><A NAME="SECTION001240000000000000000">When the clock is wrong</A></H1>
<P>
The Linux software clock is not always accurate. It is kept
running by a periodic <b>timer interrupt</b> generated by
PC hardware. If the
system has too many processes running, it may take too long to
service the timer interrupt, and the software clock starts
slipping behind.
The hardware clock runs independently and is usually more
accurate. If you boot your computer
often (as is the case for most systems that aren't servers),
it will usually keep fairly accurate time.
<P>
If you need to adjust the hardware clock, it is usually simplest
to reboot, go into the BIOS setup screen, and do it from there.
This avoids all trouble that changing system time might
cause.
If doing it via BIOS is not an option, set
the new time with <tt>date</tt><A NAME="3189"> </A> and <tt>clock</tt><A NAME="3191"> </A> (in that order),
but be prepared to reboot, if some part of the system starts
acting funny.
<P>
A networked computer (even if just over the modem) can check
its own clock automatically, by comparing it to some other
computer's time. If the other computer is known to keep
very accurate time, then both computers will keep accurate time.
This can be done by using the <tt>rdate</tt><A NAME="3193"> </A>
and <tt>netdate</tt><A NAME="3195"> </A> commands.
Both check the time of a remote computer (<tt>netdate</tt><A NAME="3197"> </A> can
handle several remote computers), and set the local computer's
time to that. By running one these commands regularly, your
computer will keep as accurate time as the remote computer.
<P>
<b>META: </b> say something intelligent about NTP
<P>
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<P><ADDRESS>
<I>Lars Wirzenius <BR>
Sat Nov 15 02:32:11 EET 1997</I>
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