453 lines
17 KiB
HTML
453 lines
17 KiB
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<html lang="en">
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<head>
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<title>Sntp User's Manual</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="Sntp User's Manual">
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<meta name="generator" content="makeinfo 4.7">
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<link title="Top" rel="top" href="#Top">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<meta http-equiv="Content-Style-Type" content="text/css">
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<style type="text/css"><!--
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span.roman { font-family: serif; font-weight: normal; }
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--></style>
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</head>
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<body>
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<h1 class="settitle">Sntp User's Manual</h1>
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<div class="node">
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<p><hr>
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<a name="Top"></a>Next: <a rel="next" accesskey="n" href="#sntp-Description">sntp Description</a>,
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Previous: <a rel="previous" accesskey="p" href="#dir">(dir)</a>,
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Up: <a rel="up" accesskey="u" href="#dir">(dir)</a>
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<br>
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</div>
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<h2 class="unnumbered">Simple Network Time Protocol User Manual</h2>
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<p>This document describes the use of the NTP Project's <code>sntp</code> program,
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that can be used to query a Network Time Protocol (NTP) server and
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display the time offset of the system clock relative to the server
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clock. Run as root, it can correct the system clock to this offset as
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well. It can be run as an interactive command or from a cron job.
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<p>This document applies to version 4.2.6p5 of <code>sntp</code>.
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<p>The program implements the SNTP protocol as defined by RFC 5905, the NTPv4
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IETF specification.
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<div class="shortcontents">
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<h2>Short Contents</h2>
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<ul>
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<a href="#Top">Simple Network Time Protocol User Manual</a>
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</ul>
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</div>
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<ul class="menu">
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<li><a accesskey="1" href="#sntp-Description">sntp Description</a>: Description
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<li><a accesskey="2" href="#sntp-Invocation">sntp Invocation</a>: Invoking sntp
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<li><a accesskey="3" href="#Usage">Usage</a>: Usage
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</ul>
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<div class="node">
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<p><hr>
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<a name="sntp-Description"></a>
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<br>
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</div>
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<!-- node-name, next, previous, up -->
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<h3 class="section">Description</h3>
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<p>By default, <code>sntp</code> writes the local data and time (i.e., not UTC) to the
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standard output in the format:
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<pre class="example"> 1996 Oct 15 20:17:25.123 +4.567 +/- 0.089 secs
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</pre>
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<p>where the +4.567 +/- 0.089 secs indicates the time offset and
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error bound of the system clock relative to the server clock.
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<div class="node">
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<p><hr>
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<a name="sntp-Invocation"></a>
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<br>
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</div>
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<h3 class="section">Invoking sntp</h3>
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<p><a name="index-sntp-1"></a><a name="index-standard-Simple-Network-Time-Protocol-program-2"></a>
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<code>sntp</code>
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can be used as a SNTP client to query a NTP or SNTP server and either display
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the time or set the local system's time (given suitable privilege). It can be
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run as an interactive command or in a
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<code>cron</code>
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job.
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<p>NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol)
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are defined and described by RFC 5905.
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<p class="indent">The default is to write the estimated correct local date and time (i.e. not
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UTC) to the standard output in a format like
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<pre class="example"> 1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 secs
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</pre>
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<p>where the
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<pre class="example"> +4.567 +/- 0.089 secs
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</pre>
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<p>indicates the local clock is 4.567 seconds behind the correct time
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(so 4.567 seconds must be added to the local clock to get it to be correct),
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and the (local) time of
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<code>1996-10-15 20:17:25.123</code>
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can be converted to UTC time by adding 8 hours and 0 minutes, and
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is believed to be correct to within
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<code>+/- 0.089</code>
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seconds.
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<p>This section was generated by <strong>AutoGen</strong>,
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the aginfo template and the option descriptions for the <span class="command">sntp</span> program. It documents the <span class="command">sntp</span> usage text and option meanings.
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<p>This software is released under a specialized copyright license.
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<ul class="menu">
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<li><a accesskey="1" href="#sntp-usage">sntp usage</a>: sntp usage help (-?)
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<li><a accesskey="2" href="#sntp-adjtime">sntp adjtime</a>: adjtime option (-j)
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<li><a accesskey="3" href="#sntp-authentication">sntp authentication</a>: authentication option (-a)
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<li><a accesskey="4" href="#sntp-broadcast">sntp broadcast</a>: broadcast option (-b)
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<li><a accesskey="5" href="#sntp-ipv4">sntp ipv4</a>: ipv4 option (-4)
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<li><a accesskey="6" href="#sntp-ipv6">sntp ipv6</a>: ipv6 option (-6)
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<li><a accesskey="7" href="#sntp-keyfile">sntp keyfile</a>: keyfile option (-k)
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<li><a accesskey="8" href="#sntp-kod">sntp kod</a>: kod option (-K)
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<li><a accesskey="9" href="#sntp-logfile">sntp logfile</a>: logfile option (-l)
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<li><a href="#sntp-normalverbose">sntp normalverbose</a>: normalverbose option (-d)
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<li><a href="#sntp-settod">sntp settod</a>: settod option (-s)
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<li><a href="#sntp-syslog">sntp syslog</a>: syslog option (-p)
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<li><a href="#sntp-timeout">sntp timeout</a>: timeout option (-t)
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</ul>
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<div class="node">
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<p><hr>
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<a name="sntp-usage"></a>Next: <a rel="next" accesskey="n" href="#sntp-adjtime">sntp adjtime</a>,
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Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
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<br>
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</div>
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<h4 class="subsection">sntp usage help (-?)</h4>
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<p><a name="index-sntp-usage-3"></a>
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This is the automatically generated usage text for sntp:
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<pre class="example">sntp - standard Simple Network Time Protocol program - Ver. 4.2.6p5
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USAGE: sntp [ -<flag> [<val>] | --<name>[{=| }<val>] ]... \
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[ hostname-or-IP ...]
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Flg Arg Option-Name Description
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-4 no ipv4 Force IPv4 DNS name resolution
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- prohibits these options:
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ipv6
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-6 no ipv6 Force IPv6 DNS name resolution
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- prohibits these options:
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ipv4
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-d no normalverbose Normal verbose
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-K Str kod KoD history filename
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-p no syslog Logging with syslog
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- prohibits these options:
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logfile
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-l Str logfile Log to specified logfile
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- prohibits these options:
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syslog
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-s no settod Set (step) the time with settimeofday()
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- prohibits these options:
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adjtime
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-j no adjtime Set (slew) the time with adjtime()
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- prohibits these options:
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settod
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-b Str broadcast Use broadcasts to the address specified for synchronisation
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-t Num timeout Specify the number of seconds to wait for broadcasts
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-a Num authentication Enable authentication with the key auth-keynumber
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-k Str keyfile Specify a keyfile. SNTP will look in this file for the key specified with -a
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opt version Output version information and exit
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-? no help Display extended usage information and exit
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-! no more-help Extended usage information passed thru pager
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-> opt save-opts Save the option state to a config file
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-< Str load-opts Load options from a config file
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- disabled as --no-load-opts
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- may appear multiple times
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Options are specified by doubled hyphens and their name or by a single
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hyphen and the flag character.
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The following option preset mechanisms are supported:
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- reading file $HOME/.ntprc
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- reading file ./.ntprc
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- examining environment variables named SNTP_*
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sntp implements the Simple Network Time Protocol, and is used to query an
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NTP or SNTP server and either display the time or set the local system's
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time (given suitable privilege).
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It can be run interactively from the command line or as a cron job.
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NTP and SNTP are defined by RFC 5905, which obsoletes RFC 4330 and RFC
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1305.
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please send bug reports to: http://bugs.ntp.org, bugs@ntp.org
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</pre>
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<div class="node">
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<p><hr>
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<a name="sntp-adjtime"></a>Next: <a rel="next" accesskey="n" href="#sntp-authentication">sntp authentication</a>,
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Previous: <a rel="previous" accesskey="p" href="#sntp-usage">sntp usage</a>,
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Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
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<br>
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</div>
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<h4 class="subsection">adjtime option (-j)</h4>
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<p><a name="index-sntp_002dadjtime-4"></a>
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This is the “set (slew) the time with adjtime()” option.
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<p>This option has some usage constraints. It:
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<ul>
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<li>must not appear in combination with any of the following options:
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settod.
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</ul>
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<div class="node">
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<p><hr>
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<a name="sntp-authentication"></a>Next: <a rel="next" accesskey="n" href="#sntp-broadcast">sntp broadcast</a>,
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Previous: <a rel="previous" accesskey="p" href="#sntp-adjtime">sntp adjtime</a>,
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Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
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<br>
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</div>
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<h4 class="subsection">authentication option (-a)</h4>
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<p><a name="index-sntp_002dauthentication-5"></a>
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This is the “enable authentication with the key auth-keynumber” option.
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This option enables authentication using the key specified in this option's argument.
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The argument of this option is the keyid, a number specified in the keyfile as this
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key's identifier. See the keyfile option (-k) for more details.
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<div class="node">
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<p><hr>
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<a name="sntp-broadcast"></a>Next: <a rel="next" accesskey="n" href="#sntp-ipv4">sntp ipv4</a>,
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Previous: <a rel="previous" accesskey="p" href="#sntp-authentication">sntp authentication</a>,
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Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
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<br>
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</div>
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<h4 class="subsection">broadcast option (-b)</h4>
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<p><a name="index-sntp_002dbroadcast-6"></a>
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This is the “use broadcasts to the address specified for synchronisation” option.
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If specified SNTP will listen to the specified broadcast address
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for NTP broadcasts. The default maximum wait time,
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68 seconds, can be modified with -t.
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<div class="node">
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<p><hr>
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<a name="sntp-ipv4"></a>Next: <a rel="next" accesskey="n" href="#sntp-ipv6">sntp ipv6</a>,
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Previous: <a rel="previous" accesskey="p" href="#sntp-broadcast">sntp broadcast</a>,
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Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
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<br>
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</div>
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<h4 class="subsection">ipv4 option (-4)</h4>
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<p><a name="index-sntp_002dipv4-7"></a>
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This is the “force ipv4 dns name resolution” option.
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<p>This option has some usage constraints. It:
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<ul>
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<li>must not appear in combination with any of the following options:
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ipv6.
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</ul>
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<p>Force DNS resolution of the following host names on the command line
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to the IPv4 namespace.
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<div class="node">
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<p><hr>
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<a name="sntp-ipv6"></a>Next: <a rel="next" accesskey="n" href="#sntp-keyfile">sntp keyfile</a>,
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Previous: <a rel="previous" accesskey="p" href="#sntp-ipv4">sntp ipv4</a>,
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Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
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<br>
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</div>
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<h4 class="subsection">ipv6 option (-6)</h4>
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<p><a name="index-sntp_002dipv6-8"></a>
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This is the “force ipv6 dns name resolution” option.
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<p>This option has some usage constraints. It:
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<ul>
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<li>must not appear in combination with any of the following options:
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ipv4.
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</ul>
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<p>Force DNS resolution of the following host names on the command line
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to the IPv6 namespace.
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<div class="node">
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<p><hr>
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<a name="sntp-keyfile"></a>Next: <a rel="next" accesskey="n" href="#sntp-kod">sntp kod</a>,
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Previous: <a rel="previous" accesskey="p" href="#sntp-ipv6">sntp ipv6</a>,
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Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
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<br>
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</div>
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<h4 class="subsection">keyfile option (-k)</h4>
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<p><a name="index-sntp_002dkeyfile-9"></a>
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This is the “specify a keyfile. sntp will look in this file for the key specified with -a” option.
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This option specifies the keyfile. SNTP will search for the key specified with -a keyno in this
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file. Key files follow the following format:
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<p>keyid keytype key
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<p>Where keyid is a number identifying this key
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keytype is one of the follow:
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S Key in 64 Bit hexadecimal number as specified in in the DES specification.
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N Key in 64 Bit hexadecimal number as specified in the NTP standard.
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A Key in a 1-to-8 character ASCII string.
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M Key in a 1-to-8 character ASCII string using the MD5 authentication scheme.
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<p>For more information see ntp.keys(5).
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<div class="node">
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<p><hr>
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<a name="sntp-kod"></a>Next: <a rel="next" accesskey="n" href="#sntp-logfile">sntp logfile</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="#sntp-keyfile">sntp keyfile</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">kod option (-K)</h4>
|
||
|
|
|
||
|
|
<p><a name="index-sntp_002dkod-10"></a>
|
||
|
|
This is the “kod history filename” option.
|
||
|
|
Specifies the filename to be used to persist the history of KoD
|
||
|
|
responses received from servers. The default is
|
||
|
|
/var/db/ntp-kod.
|
||
|
|
|
||
|
|
<div class="node">
|
||
|
|
<p><hr>
|
||
|
|
<a name="sntp-logfile"></a>Next: <a rel="next" accesskey="n" href="#sntp-normalverbose">sntp normalverbose</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="#sntp-kod">sntp kod</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">logfile option (-l)</h4>
|
||
|
|
|
||
|
|
<p><a name="index-sntp_002dlogfile-11"></a>
|
||
|
|
This is the “log to specified logfile” option.
|
||
|
|
|
||
|
|
<p>This option has some usage constraints. It:
|
||
|
|
<ul>
|
||
|
|
<li>must not appear in combination with any of the following options:
|
||
|
|
syslog.
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<p>This option causes the client to write log messages to the specified
|
||
|
|
logfile.
|
||
|
|
|
||
|
|
<div class="node">
|
||
|
|
<p><hr>
|
||
|
|
<a name="sntp-normalverbose"></a>Next: <a rel="next" accesskey="n" href="#sntp-settod">sntp settod</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="#sntp-logfile">sntp logfile</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">normalverbose option (-d)</h4>
|
||
|
|
|
||
|
|
<p><a name="index-sntp_002dnormalverbose-12"></a>
|
||
|
|
This is the “normal verbose” option.
|
||
|
|
Diagnostic messages for non-fatal errors and a limited amount of
|
||
|
|
tracing should be written to standard error. Fatal ones always
|
||
|
|
produce a diagnostic. This option should be set when there is a
|
||
|
|
suspected problem with the server, network or the source.
|
||
|
|
|
||
|
|
<div class="node">
|
||
|
|
<p><hr>
|
||
|
|
<a name="sntp-settod"></a>Next: <a rel="next" accesskey="n" href="#sntp-syslog">sntp syslog</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="#sntp-normalverbose">sntp normalverbose</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">settod option (-s)</h4>
|
||
|
|
|
||
|
|
<p><a name="index-sntp_002dsettod-13"></a>
|
||
|
|
This is the “set (step) the time with settimeofday()” option.
|
||
|
|
|
||
|
|
<p>This option has some usage constraints. It:
|
||
|
|
<ul>
|
||
|
|
<li>must not appear in combination with any of the following options:
|
||
|
|
adjtime.
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<div class="node">
|
||
|
|
<p><hr>
|
||
|
|
<a name="sntp-syslog"></a>Next: <a rel="next" accesskey="n" href="#sntp-timeout">sntp timeout</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="#sntp-settod">sntp settod</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">syslog option (-p)</h4>
|
||
|
|
|
||
|
|
<p><a name="index-sntp_002dsyslog-14"></a>
|
||
|
|
This is the “logging with syslog” option.
|
||
|
|
|
||
|
|
<p>This option has some usage constraints. It:
|
||
|
|
<ul>
|
||
|
|
<li>must not appear in combination with any of the following options:
|
||
|
|
logfile.
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<p>When this option is set all logging will be done using syslog.
|
||
|
|
|
||
|
|
<div class="node">
|
||
|
|
<p><hr>
|
||
|
|
<a name="sntp-timeout"></a>Previous: <a rel="previous" accesskey="p" href="#sntp-syslog">sntp syslog</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">timeout option (-t)</h4>
|
||
|
|
|
||
|
|
<p><a name="index-sntp_002dtimeout-15"></a>
|
||
|
|
This is the “specify the number of seconds to wait for broadcasts” option.
|
||
|
|
When waiting for a broadcast packet SNTP will wait the number
|
||
|
|
of seconds specified before giving up. Default 68 seconds.
|
||
|
|
|
||
|
|
<div class="node">
|
||
|
|
<p><hr>
|
||
|
|
<a name="Usage"></a>
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<!-- node-name, next, previous, up -->
|
||
|
|
<h3 class="section">Usage</h3>
|
||
|
|
|
||
|
|
<p>The simplest use of this program is as an unprivileged command to
|
||
|
|
check the current time, offset, and error in the local clock.
|
||
|
|
For example:
|
||
|
|
|
||
|
|
<pre class="example"> sntp ntpserver.somewhere
|
||
|
|
</pre>
|
||
|
|
<p>With suitable privilege, it can be run as a command or in a
|
||
|
|
<code>crom</code> job to reset the local clock from a reliable server, like
|
||
|
|
the <code>ntpdate</code> and <code>rdate</code> commands.
|
||
|
|
For example:
|
||
|
|
|
||
|
|
<pre class="example"> sntp -a ntpserver.somewhere
|
||
|
|
</pre>
|
||
|
|
</body></html>
|
||
|
|
|