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xntpd - Network Time Protocol (NTP) daemon
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<code>xntpd</code> - Network Time Protocol (NTP) daemon
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      <p><h4>Synopsis</h4>

      <p><code>xntpd [ -aAbdm ] [ -c <i>conffile</i> ] [ -f
      <i>driftfile</i> ] [ -k <i>keyfile</i> ] [ -l <i>logfile</i> ] [
      -p <i>pidfile</i> ] [ -r <i>broadcastdelay</i> ] [ -s
      <i>statsdir</i> ] [ -t <i>key</i> ] [ -v <i>variable</i> ] [ -V
      <i>variable</i> ]</code>

      <p><h4>Description</h4>

      <p><code>xntpd</code> is an operating system daemon which sets and
      maintains the system time-of-day in synchronism with Internet
      standard time servers. <code>xntpd</code> is a complete
      implementation of the Network Time Protocol (NTP) version 3, as
      defined by RFC-1305, but also retains compatibility with version 1
      and 2 servers as defined by RFC- 1059 and RFC-1119,
      respectively. <code>xntpd</code> does all computations in 64-bit
      fixed point arithmetic and requires no floating point
      support. While the ultimate precision of this design, about 232
      picoseconds, is not achievable with ordinary workstations and
      networks of today, it may be required with future nanosecond CPU
      clocks and gigabit LANs.

      <p>The daemon can operate in any of several modes, including
      symmetric active/passive, client/server and broadcast/multicast,
      as described in RFC-1305. A broadcast/multicast client can
      discover remote servers, compute server-client propagation delay
      correction factors and configure itself automatically. This makes
      it possible to deploy a fleet of workstations without specifying
      configuration details specific to the local environment.

      <p>Ordinarily, <code>xntpd</code> reads the <code>ntp.conf</code>
      configuration file at startup time in order to determine the
      synchronization sources and operating modes. It is also possible
      to specify a working, although limited, configuration entirely on
      the command line, obviating the need for a configuration
      file. This may be particularly appropriate when the local host is
      to be configured as a broadcast or multicast client, with all
      peers being determined by listening to broadcasts at run time.

      <p>Various internal <code>xntpd</code> variables can be displayed
      and configuration options altered while the daemon is running
      using the <a href = "ntpq.html"> <code>ntpq</code></a> and <a href
      = "xntpdc.html"><code>xntpdc</code></a> utility programs.

      <p>When <code>xntpd</code> starts it looks at the value of
      <code>umask</code>, and if it's zero <code>xntpd</code> will set
      the <code>umask</code> to <code>022</code>.

<p><h4>Command Line Options</h4>

<dl>

<dt><code>-a</code>
<dd>Enable authentication mode. The default is enabled, so this option
is obsolete now.

<dt><code>-A</code>
<dd>Disable authentication mode.

<p><dt><code>-b</code>
<dd>Synchronize using NTP broadcast messages.

<p><dt><code>-c <i>conffile</i></code>
<dd>Specify the name and path of the configuration file.

<p><dt><code>-d</code>
<dd>Specify debugging mode. This flag may occur multiple times, with
each occurrence indicating greater detail of display.
<p><dt><code>-f <i>driftfile</i></code>
<dd>Specify the name and path of the drift file.

<p><dt><code>-k <i>keyfile</i></code>
<dd>Specify the name and path of the file containing the NTP
authentication keys.

<p><dt><code>-l <i>logfile</i></code>
<dd>Specify the name and path of the log file. The default is the system
log facility.

<p><dt><code>-m</code>
<dd>Synchronize using NTP multicast messages on the IP multicast group
address 224.0.1.1 (requires multicast kernel).

<p><dt><code>-p <i>pidfile</i></code>
<dd>Specify the name and path to record the daemon's process ID.

<p><dt><code>-r <i>broadcastdelay</i></code>
<dd>Specify the default propagation delay from the broadcast/multicast
server and this computer. This is used only if the delay cannot be
computed automatically by the protocol.

<p><dt><code>-s <i>statsdir</i></code>
<dd>Specify the directory path for files created by the statistics
facility.

<p><dt><code>-t <i>key</i></code>
<dd>Add a key number to the trusted key list.

<p><dt><code>-v <i>variable</i></code>
<dd>Add a system variable.

<p><dt><code>-V <i>variable</i></code>
<dd>Add a system variable listed by default.

</dl>

<p><h4>The Configuration File</h4>

<p>The <code>xntpd</code> configuration file is read at initial startup
in order to specify the synchronization sources, modes and other related
information. Usually, it is installed in the <code>/etc</code>
directory, but could be installed elsewhere (see the <code>-c
<i>conffile</i></code> command line option). The file format is similar
to other Unix configuration files - comments begin with a <code>#</code>
character and extend to the end of the line; blank lines are ignored.
Configuration commands consist of an initial keyword followed by a list
of arguments, some of which may be optional, separated by whitespace.
Commands may not be continued over multiple lines. Arguments may be host
names, host addresses written in numeric, dotted-quad form, integers,
floating point numbers (when specifying times in seconds) and text
strings. Optional arguments are delimited by <code>[ ]</code> in the
following descriptions, while alternatives are separated by
<code>|</code>. The notation [ ... ] means an optional, indefinite
repetition of the last item before the [ ... ].

<p>See the following pages for configuration and control options. While
there is a rich set of options available, the only required option is
one or more <code>server, peer</code> or <code>broadcast</code> commands
described in the Configuration Options page. The <a href = "notes.html">
Notes on Configuring NTP and Setting up a NTP Subnet </a> page contains
an extended discussion of these options.

<p><a href="confopt.html"> Configuration Options </a>
<br><a href="authopt.html"> Authentication Options </a>
<br><a href="monopt.html"> Monitoring Options </a>
<br><a href="accopt.html"> Access Control Options </a>
<br><a href="clockopt.html"> Reference Clock Options </a>
<br><a href="miscopt.html"> Miscellaneous Options </a>

<p><h4>Files</h4>

<p><code>/etc/ntp.conf</code> - the default name of the configuration
file
<br><code>/etc/ntp.drift</code> - the default name of the drift file
<br><code>/etc/ntp.keys</code> - the default name of the key file

<p><h4>Bugs</h4>

<p><code>xntpd</code> has gotten rather fat. While not huge, it has gotten
larger than might be desireable for an elevated-priority daemon running
on a workstation, particularly since many of the fancy features which
consume the space were designed more with a busy primary server, rather
than a high stratum workstation, in mind.

<hr><address>David L. Mills (mills@udel.edu)</address></body></html>
