Walt Kelly</a>
<p>The chicken is getting configuration advice.</p>
<p>Last update:
- <!-- #BeginDate format:En2m -->24-Sep-2009 16:12<!-- #EndDate -->
+ <!-- #BeginDate format:En2m -->25-Nov-2009 4:46<!-- #EndDate -->
</p>
<br clear="left">
<h4>Related Links</h4>
<script type="text/javascript" language="javascript" src="scripts/confopt.txt"></script>
<h4>Table of Contents</h4>
<ul>
- <li class="inline"><a href="#cfg">Configuration Commands</a>
- <li class="inline"><a href="#opt">Command Options</a>
- <li class="inline"><a href="#aux">Auxilliary Commands</a>
- <li class="inline"><a href="#bug">Bugs</a>
+ <li class="inline"><a href="#cfg">Configuration Commands</a></li>
+ <li class="inline"><a href="#opt">Command Options</a></li>
+ <li class="inline"><a href="#aux">Auxilliary Commands</a></li>
+ <li class="inline"><a href="#bug">Bugs</a></li>
</ul>
<hr>
<p>Following is a description of the configuration commands in NTPv4. There are
<tt>broadcast <i>address</i> [options ...]</tt><br>
<tt>manycastclient <i>address</i> [options ...]</tt><br>
<tt>pool <i>address</i> [options ...]</tt><br>
- <tt>unpeer [<i>address</i> | <i>associd</i>]</tt>
+ <tt>unpeer [<i>address</i> | <i>associd</i>]</tt></dt>
<dd>These commands specify the time server name or address to be used and the
mode in which to operate. The <i>address</i> can be either a DNS name or a
IPv4 or IPv6 address in standard notation. In general, multiple commands of
each type can be used for different server and peer addresses or multicast
groups.
<dl>
- <dt><tt>server</tt>
+ <dt><tt>server</tt></dt>
<dd>For type s and r addresses (only), this command mobilizes a persistent
client mode association with the specified remote server or local reference
clock. If the <tt>preempt</tt> flag is specified, a preemptable client mode
- association is mobilized instead.
- <dt><tt>peer</tt>
+ association is mobilized instead.</dd>
+ <dt><tt>peer</tt></dt>
<dd>For type s addresses (only), this command mobilizes a persistent symmetric-active
- mode association with the specified remote peer.
- <dt><tt>broadcast</tt>
+ mode association with the specified remote peer.</dd>
+ <dt><tt>broadcast</tt></dt>
<dd>For type b and m addressees (only), this command mobilizes a persistent
broadcast or multicast server mode association. Note that type
b messages go only to the interface specified, but type m messages go to
- all interfaces.
- <dt><tt>manycastclient</tt>
+ all interfaces.</dd>
+ <dt><tt>manycastclient</tt></dt>
<dd>For type m addresses (only), this command mobilizes a manycast client
mode association for the multicast group address specified. In this mode
the address must match the address specified on the <tt>manycastserver</tt> command
- of one or more designated manycast servers.
- <dt><tt>pool</tt>
+ of one or more designated manycast servers.</dd>
+ <dt><tt>pool</tt></dt>
<dd>For type s messages (only) this command mobilizes a client mode association
for servers implementing the pool automatic server discovery scheme described
on the <a href="assoc.html">Association Management</a> page. The address
is a DNS name in the form <tt><i>area</i>.pool.ntp.org</tt>, where <tt><i>area</i></tt> is
- a qualifier designating the server geographic area such as <tt>us</tt> or <tt>europe</tt>.
- <dt><tt>unpeer</tt>
+ a qualifier designating the server geographic area such as <tt>us</tt> or <tt>europe</tt>.</dd>
+ <dt><tt>unpeer</tt></dt>
<dd>This command removes a previously configured association. An address or association ID can
be used to identify the association. Either an IP address or DNS name can be used. This
command is most useful when supplied via <tt><a href="ntpq.html">ntpq</a></tt> runtime
- configuration commands <tt>:config</tt> and <tt>config-from-file</tt>.
- </dl>
+ configuration commands <tt>:config</tt> and <tt>config-from-file</tt>.</dd>
+ </dl></dd>
</dl>
<h4 id="opt">Command Options</h4>
<dl>
- <dt><tt>autokey</tt>
+ <dt><tt>autokey</tt></dt>
<dd>Send and receive packets authenticated by the Autokey scheme described
in the <a href="authopt.html">Authentication Options</a> page. This option
- is mutually exclusive with the <tt>key</tt> option.
- <dt><tt>burst</tt>
+ is mutually exclusive with the <tt>key</tt> option.</dd>
+ <dt><tt>burst</tt></dt>
<dd>When the server is reachable, send a burst of eight packets instead of the
usual one. The packet spacing is normally 2 s; however, the spacing between
the first and second packets can be changed with the <a href="miscopt.html"><tt>calldelay</tt></a> command
to allow additional time for a modem or ISDN call to complete. This option
is valid only with the <tt>server</tt> command and type s addressesa.
It is a recommended option when the <tt>maxpoll</tt> option is greater than
- 10 (1024 s).
- <dt><tt>dynamic</tt>
- <dd>Allows a server/peer to be configured even if it is not reachable at configuration
- time. It is assumed that at some point in the future the network environment
- changes so that this server/peer can be reached. This option is useful
- to configure servers/peers on mobile systems with intermittent network
- access (e.g. WLAN clients). Note: the current implementation does not
- support this option.
- <dt><tt>iburst</tt>
+ 10 (1024 s).</dd>
+ <dt><tt>iburst</tt></dt>
<dd>When the server is unreachable, send a burst of eight packets instead of
the usual one. The packet spacing is normally 2 s; however, the spacing between
the first and second packets can be changed with the <a href="miscopt.html"><tt>calldelay</tt></a> command
to allow additional time for a modem or ISDN call to complete. This option
is valid only with the <tt>server</tt> command and type s addresses. It is
- a recommended option with this command.
- <dt><tt>key</tt> <i><tt>key</tt></i>
+ a recommended option with this command.</dd>
+ <dt><tt>key</tt> <i><tt>key</tt></i></dt>
<dd>Send and receive packets authenticated by the symmetric key scheme described
in the <a href="authopt.html">Authentication Options</a> page.
The <i><tt>key</tt></i> specifies the key identifier with values from 1 to
- 65534, inclusive. This option is mutually exclusive with the <tt>autokey</tt> option.
+ 65534, inclusive. This option is mutually exclusive with the <tt>autokey</tt> option.</dd>
<dt><tt>minpoll <i>minpoll<br>
- </i></tt><tt>maxpoll <i>maxpoll</i></tt>
+ </i></tt><tt>maxpoll <i>maxpoll</i></tt></dt>
<dd>These options specify the minimum and maximum poll intervals for NTP messages,
in seconds as a power of two. The maximum poll interval defaults to 10
(1024 s), but can be increased by the <tt>maxpoll</tt> option to an upper limit
of 17 (36 h). The minimum poll interval defaults to 6 (64 s), but can
- be decreased by the <tt>minpoll</tt> option to a lower limit of 3 (8 s).
- <dt><tt>mode <i>option</i></tt>
+ be decreased by the <tt>minpoll</tt> option to a lower limit of 3 (8 s).</dd>
+ <dt><tt>mode <i>option</i></tt></dt>
<dd>Pass the <tt><i>option</i></tt> to a reference clock driver, where <tt><i>option</i></tt> is
an integer in the range from 0 to 255, inclusive. This option is valid
- only with type r addresses.
- <dt><tt>noselect</tt>
+ only with type r addresses.</dd>
+ <dt><tt>noselect</tt></dt>
<dd>Marks the server or peer to be ignored by the selection algorithm but visible
- to the monitoring program. This option is ignored with the <tt>broadcast</tt> command.
- <dt><tt>preempt</tt>
+ to the monitoring program. This option is ignored with the <tt>broadcast</tt> command.</dd>
+ <dt><tt>preempt</tt></dt>
<dd>Specifies the association as preemptable rather than the default persistent.
This option is ignored with the <tt>broadcast</tt> command and is most useful
- with the <tt>manycastclient</tt> and <tt>pool</tt> commands.
- <dt><tt>prefer</tt>
+ with the <tt>manycastclient</tt> and <tt>pool</tt> commands.</dd>
+ <dt><tt>prefer</tt></dt>
<dd>Mark the server as preferred. All other things being equal, this host will
be chosen for synchronization among a set of correctly operating hosts. See
the <a href="prefer.html">Mitigation Rules and the <tt>prefer</tt> Keyword</a> page
- for further information. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.
- <dt><tt>true</tt>
+ for further information. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd>
+ <dt><tt>true</tt></dt>
<dd>Mark the association to assume truechimer status; that is, always survive
the selection and clustering algorithms. This option can be used with any association,
but is most useful for reference clocks with large jitter on the serial port
and precision pulse-per-second (PPS) signals. Caution: this option defeats
the algorithms designed to cast out falsetickers and can allow these sources
- to set the system clock. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.
- <dt><tt>ttl <i>ttl</i></tt>
+ to set the system clock. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd>
+ <dt><tt>ttl <i>ttl</i></tt></dt>
<dd>This option specifies the time-to-live <i><tt>ttl</tt></i> for the <tt>broadcast</tt> command
and the maximum <i><tt>ttl</tt></i> for the expanding ring search used by the <tt>manycastclient</tt> command.
- Selection of the proper value, which defaults to 127, is something of
- a black art and should be coordinated with the network administrator.
- This option is invalid with type r addresses.<dt><tt>version <i>version</i></tt>
- <dd>Specifies the version number to be used for outgoing NTP packets. Versions
- 1-4 are the choices, with version 4 the default.
- <dt><tt>xleave</tt>
+ Selection of the proper value, which defaults to 127, is something of a black art and should be coordinated with the network administrator. This option is invalid with type r addresses.</dd>
+ <dt><tt>version <i>version</i></tt></dt>
+ <dd>Specifies the version number to be used f
+or outgoing NTP packets. Versions
+ 1-4 are the choices, with version 4 the default.</dd>
+ <dt><tt>xleave</tt></dt>
<dd>Operate in interleaved mode (symmetric and broadcast modes only). (see <a href="xleave.html">NTP
- Interleaved Modes</a>)
+ Interleaved Modes</a>)</dd>
</dl>
<h4 id="aux">Auxilliary Commands</h4>
<dl>
- <dt id="broadcastclient"><tt>broadcastclient</tt>
+ <dt id="broadcastclient"><tt>broadcastclient</tt></dt>
<dd>Enable reception of broadcast server messages to any local interface (type
b address). Ordinarily, upon receiving a broadcast message for the first
time, the broadcast client measures the nominal server propagation delay using
should operate using symmetric key or public key authentication as described
in the <a href="authopt.html">Authentication
Options</a> page. Note that the <tt>novolley</tt> keyword is incompatible with
- public key authentication.
- <dt id="manycastserver"><tt>manycastserver <i>address</i> [...]</tt>
+ public key authentication.</dd>
+ <dt id="manycastserver"><tt>manycastserver <i>address</i> [...]</tt></dt>
<dd>Enable reception of manycast client messages (type m)to the multicast group
address(es) (type m) specified. At least one address is required. Note that,
in order to avoid accidental or malicious disruption, both the server and client
should operate using symmetric key or public key authentication as described
- in the <a href="authopt.html">Authentication Options</a> page.
- <dt id="multicastclient"><tt>multicastclient <i>address</i> [...]</tt>
+ in the <a href="authopt.html">Authentication Options</a> page.</dd>
+ <dt id="multicastclient"><tt>multicastclient <i>address</i> [...]</tt></dt>
<dd>Enable reception of multicast server messages to the multicast group address(es)
(type m) specified. Upon receiving a message for the first time, the multicast
client measures the nominal server propagation delay using a brief client/server
synchronizes to succeeding multicast messages. Note that, in order to avoid
accidental or malicious disruption in this mode, both the server and client
should operate using symmetric key or public key authentication as described
- in the <a href="authopt.html">Authentication Options</a> page.
+ in the <a href="authopt.html">Authentication Options</a> page.</dd>
</dl>
<h4 id="bug">Bugs</h4>
<p>The syntax checking is not picky; some combinations of ridiculous and even
<h3>Quick Start</h3>
<img src="pic/panda.gif" alt="gif" align="left">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/%7emills/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.</p>
- <p>Last update: <csobj format="ShortTime" h="25" locale="00000409" region="0" t="DateTime" w="61">16:25</csobj> UTC <csobj format="LongDate" h="25" locale="00000409" region="0" t="DateTime" w="250">Sunday, March 02, 2008</csobj></p>
- <h4>Related Links</h4>
+ <p>Last update:
+ <!-- #BeginDate format:En1m -->25-nov-09 22:13<!-- #EndDate -->
+ UTC</p>
+ <h4>Related Links</h4>
<script type="text/javascript" language="javascript" src="scripts/install.txt"></script>
<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 is to build the distribution for the particular workstation and install in the usual place. The <a href="build.html">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. The file, called by default <tt>/etc/ntp.conf</tt>, need only contain one command 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. There are about two dozen public time servers operated by the <a href="http://tf.nist.gov/tf-cgi/servers.cgi">National Institutes of Science and Technology (NIST)</a>, <a href="http://tycho.usno.navy.mil/ntp.html">US Naval Observatory (USNO)</a>, <a href="http://inms-ienm.nrc-cnrc.gc.ca/time_services/network_time_protocol_e.html"> Canadian Metrology Centre (CMC)</a> and many others available on the Internet. Lists of public primary and secondary NTP servers maintained on the <a href="http://support.ntp.org/bin/view/Servers/WebHome">Public NTP Time Servers</a> page, which is updated frequently.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 occasionally writes the current value to a file specified by the</p>
+ <p>Choosing an appropriate remote server is somewhat of a black art, but a
+ suboptimal choice is seldom a problem. The simplest is to use the
+ Server Pool Scheme on the <a href="manyopt.html">Automatic Server Discovery</a> page. There
+ are about two dozen public time servers operated by the <a href="http://tf.nist.gov/tf-cgi/servers.cgi">National
+ Institutes of Science and Technology (NIST)</a>, <a href="http://tycho.usno.navy.mil/ntp.html">US
+ Naval Observatory (USNO)</a>, <a href="http://inms-ienm.nrc-cnrc.gc.ca/time_services/network_time_protocol_e.html"> Canadian
+ Metrology Centre (CMC)</a> and many others available on the Internet. Lists
+ of public primary and secondary NTP servers maintained on the <a href="http://support.ntp.org/bin/view/Servers/WebHome">Public
+ NTP Time Servers</a> page, which is updated frequently.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 occasionally writes the current value to a file specified by the</p>
<p><tt>driftfile /etc/ntp.drift</tt></p>
<p>configuration command. If <tt>ntpd</tt> is stopped and restarted, it initializes the frequency from this file and avoids the potentially lengthy interval to relearn the correction.</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>
projects / thirdparty / ntp.git / commitdiff
