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Fri Sep 7 14:54:47 2001 UTC (22 years, 8 months ago) by harris41
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<TITLE>LON-CAPA Time Synchronization</TITLE>
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<H1>LON-CAPA Time Synchronization</H1>
<P>
Scott Harrison
</P>
<P>
Last updated: 02/07/2001
</P>
<P>
This file describes issues associated with LON-CAPA
and time synchronization.
</P>
<H3>Importance</H3>
<P>
Since LON-CAPA machines are involved with
the submission of homework, quizzes, and
exams to the instructor, it is important that
the time of the server be kept accurately and precisely.
</P>
<P>
Accuracy involves 
</P>
<pre>
I will explain the components of ntp and how they
interrelate on a LON-CAPA system

There are three relevant components here:
1. a correct /etc/ntp/step-tickers,
2. a correct /etc/ntp.conf
3. enabling xntpd for boot up

Without /etc/ntp.conf, /etc/rc.d/init.d/xntpd won't do anything.
With /etc/ntp.conf but without /etc/ntp/step-tickers, Gerd is correct
when he says:

> What I do know is that if the clock in the CMOS is off by too much,the normal
> ntp will not work. Instead, the clock has to be forced to synch initially,and
> from then on can be automatically adjusted.

The unix commands for Gerd's manual approach are:
/etc/rc.d/init.d/xntpd stop
/usr/sbin/ntpdate ntp.msu.edu (or whatever your ntp server is)
/etc/rc.d/init.d/xntpd start

To force xntpd to avoid the offset problem, defining
/etc/ntp/step-tickers does the trick.

With /etc/ntp.conf and /etc/ntp/step-tickers, xntp still may not
work (depending on whether the last instruction was followed
for the LON-CAPA installation, see
http://install.lon-capa.org/docs/3.1/instructions_with_cd.html)

Making sure xntp starts up upon boot time should simply
be a matter of:

/sbin/chkconfig xntpd on

Finally, the correct settings for /etc/ntp.conf
and /etc/ntp/step-tickers are:

1 line with the ip address of your ntp server

For instance:

echo "whistler.sfu.ca" > /etc/ntp/step-tickers
echo "whistler.sfu.ca" > /etc/ntp.conf

Everyone is currently setting these and other LON-CAPA conf
files manually after cvs upgrades, because
there were several parties who were

* doing different things
* in different ways
* for different reasons
* for different institutions
* for their machine-specific configurations

I was not able to make everyone happy with
"make configinstall".  For the future, we (Guy and I) do think
we've come up with a new way to do everything
for everyone for updating configuration files
as the CVS source repository changes.

-Scott
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