freebsd-dev/contrib/ntp/html/quick.htm
2001-08-29 14:35:15 +00:00

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<h3>Quick Start</h3>
<img align="left" src="pic/panda.gif" alt="gif">FAX test image for
SATNET (1979).
<p>The baby panda was scanned at University College London and used
as a FAX test image for a demonstration of the DARPA Atlantic
SATNET Program and the first transatlantic Internet connection in
1978. The computing system used for that demonstration was called
the <a href=
"http://www.eecis.udel.edu/~mills/database/papers/fuzz.ps">
Fuzzball</a> . As it happened, this was also the first Internet
multimedia presentation and the first to use NTP in regular
operation. The image was widely copied and used for testing purpose
throughout much of the 1980s.<br clear="left">
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<hr>
<p>For the rank amateur the sheer volume of the documentation
collection must be intimidating. However, it doesn't take much to
fly the <tt>ntpd</tt> daemon with a simple configuration where a
workstation needs to synchronize to some server elsewhere in the
Internet. The first thing that needs to be done is to build the
distribution for the particular workstation and install in the
usual place. The <a href="build.htm">Building and Installing the
Distribution</a> page describes how to do this.</p>
<p>While it is possible that certain configurations do not need a
configuration file, most do require one. Strictly speaking, the
file need only contain one line specifying a remote server, for
instance</p>
<p><tt>server foo.bar.com</tt></p>
<p>Choosing an appropriate remote server is somewhat of a black
art, but a suboptimal choice is seldom a problem. Links to public
time servers operated by National Institutes of Science and
Technology (NIST), US Naval Observatory (USNO), Canadian Metrology
Centre (CMC) and many others are given in the home page of this
document collection. The lists are sorted by country and, in the
case of the US, by state. Usually, the best choice is the nearest
in geographical terms, but the terms of engagement specified in
each list entry should be carefully respected.</p>
<p>During operation <tt>ntpd</tt> measures and corrects for
incidental clock frequency error and writes the current value to a
file if enabled. If the <tt>ntpd</tt> is stopped and restarted, it
initializes the frequency from this file. In this way the
potentially lengthy interval to relearn the frequency error is
avoided. Thus, for most applications an additional line should be
added to the file of the form</p>
<p><tt>driftfile /etc/ntp.drift</tt></p>
<p>That's all there is to it, unless some problem in network
connectivity or local operating system configuration occurs. The
most common problem is some firewall between the workstation and
server. System administrators should understand NTP uses UDP port
123 as both the source and destination port and that NTP does not
involve any operating system interaction other than to set the
system clock. While almost all modern Unix systems have included
NTP and UDP port 123 defined in the services file, this should be
checked if <tt>ntpd</tt> fails to come up at all.</p>
<p>The best way to confirm NTP is working is using the <a href=
"ntpq.htm"><tt>ntpq</tt></a> utility, although the <a href=
"ntpdc.htm"><tt>ntpdc</tt></a> utility may be useful in extreme
cases. See the documentation pages for further information. In the
most extreme cases the <tt>-d</tt> option on the <tt>ntpd</tt>
command line results in a blow-by-blow trace of the daemon
operations. While the trace output can be cryptic, to say the
least, it gives a general idea of what the program is doing and, in
particular, details the arriving and departing packets and detected
errors, if present.</p>
<p>Sometimes the <tt>ntpd</tt>. behavior may seem to violate the
Principle of Least Astonishment, but there are good reasons for
this. See the <a href="ntpd.htm">Network Time Protocol (NTP)
daemon</a> page for revealing insights. See this page and its
dependencies for additional configuration and control options. The
<a href="notes.htm">Notes on Configuring NTP and Setting up a NTP
Subnet</a> page contains an extended discussion of these
options.</p>
<hr>
<a href="index.htm"><img align="left" src="pic/home.gif" alt=
"gif"></a>
<address><a href="mailto:mills@udel.edu">David L. Mills
&lt;mills@udel.edu&gt;</a></address>
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