from here

Introduction

What is NTP? It is a UDP protocol for correcting system clocks.

Why
am I using it? I’ve got a couple of Debian based machines running on
VMWare, and the clock keeps going out of sync. I want to have as little
overhead on these boxes as possible, so I set up an NTP Daemon on the
VMWare host, and then the NTP Clients on the VMWare Guests.

My Sources

I followed this guide, but it was a little unclear, so I figured I’d follow it up and add my notes to the mix.

Setting up the server

Firstly,
I had to get the NTPd running on the server. The Host machine is
running Debian, but if you aren’t, then provided you can install an NTP
server on the server, you’ll be OK.

I installed ntpdate and ntp from the Debian repositories using the following apt command:

apt-get install ntp ntpdate</pre>Next, I stopped the NTPd using this command:<pre>/etc/init.d/ntp stop</pre>I
then ran the ntpdate command (which won't run while the ntpd is
running) to bring the clock into sync with the upstream server:<pre>ntpdate pool.ntp.org</pre>If you've got a more local NTP server, use that in place of the pool.ntp.org. <br /><br />Next, use the date command to ensure the clock is closer to being in sync.<br /><br /><div class="blogPost"><li>If
you've got a local NTP server, you should edit the file /etc/ntp.conf
and either add to the server lines (if you also want to keep access to
the existing pool of NTP servers) or comment out the existing server
lines.</li><br /><li>Add your server in the format (where the server's IP address is 111.222.333.444):<pre>server 111.222.333.444</pre></li>Start the NTP daemon using the command:<pre>/etc/init.d/ntp start</pre>Finally, type the following command:<pre>ntpq -p</pre>This may take a few moments, but should return some sort of text like the following:<pre>     remote           refid      st t when poll reach   delay   offset  jitter<br />==============================================================================<br /> 11.111.11.11    222.222.2.222    2 u   21   64  377    0.603   65.748   7.470<br />

Setting up the clients

Essentially,
the steps here are exactly the same as with the server, except, where
you point all of your NTP sources at a common IP address for the host
machine.