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diff --git a/contrib/ntp/html/ntpdate.htm b/contrib/ntp/html/ntpdate.htm index a7f532f..c2d32bb 100644 --- a/contrib/ntp/html/ntpdate.htm +++ b/contrib/ntp/html/ntpdate.htm @@ -1,185 +1,186 @@ -<HTML> -<HEAD> - <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> - <META NAME="GENERATOR" CONTENT="Mozilla/4.01 [en] (Win95; I) [Netscape]"> - <TITLE>ntpdate - set the date and time via NTP -</TITLE> -</HEAD> -<BODY> - -<H3> -<TT>ntpdate</TT> - set the date and time via NTP</H3> - -<HR> -<H4> -Synopsis</H4> -<TT>ntpdate [ -bBdoqsuv ] [ -a <I>key</I> ] [ -e <I>authdelay</I> ] [ -k -<I>keyfile</I> ] [ -o <I>version</I> ] [ -p <I>samples</I> ] [ -t <I>timeout</I> -] <I>server</I> [ ... ]</TT> -<H4> -Description</H4> -<TT>ntpdate</TT> sets the local date and time by polling the Network Time -Protocol (NTP) server(s) given as the <I>server</I> arguments to determine -the correct time. It must be run as root on the local host. A number of -samples are obtained from each of the servers specified and a subset of -the NTP clock filter and selection algorithms are applied to select the -best of these. Note that the accuracy and reliability of <TT>ntpdate</TT> -depends on the number of servers, the number of polls each time it is run -and the interval between runs. - -<P><TT>ntpdate</TT> can be run manually as necessary to set the host clock, -or it can be run from the host startup script to set the clock at boot -time. This is useful in some cases to set the clock initially before starting -the NTP daemon <TT>ntpd</TT>. It is also possible to run <TT>ntpdate</TT> -from a <TT>cron</TT> script. However, it is important to note that <TT>ntpdate</TT> -with contrived <TT>cron</TT> scripts is no substitute for the NTP daemon, -which uses sophisticated algorithms to maximize accuracy and reliability -while minimizing resource use. Finally, since <TT>ntpdate</TT> does not -discipline the host clock frequency as does <TT>ntpd</TT>, the accuracy -using <TT>ntpdate</TT> is limited. - -<P>Time adjustments are made by <TT>ntpdate</TT> in one of two ways. If -<TT>ntpdate</TT> determines the clock is in error more than 0.5 second -it will simply step the time by calling the system <TT>settimeofday()</TT> -routine. If the error is less than 0.5 seconds, it will slew the time by -calling the system <TT>adjtime()</TT> routine. The latter technique is -less disruptive and more accurate when the error is small, and works quite -well when <TT>ntpdate</TT> is run by <TT>cron</TT> every hour or two. - -<P><TT>ntpdate</TT> will decline to set the date if an NTP server daemon -(e.g., <TT>ntpd</TT>) is running on the same host. When running <TT>ntpdate</TT> -on a regular basis from <TT>cron</TT> as an alternative to running a daemon, -doing so once every hour or two will result in precise enough timekeeping -to avoid stepping the clock. - -<P>If NetInfo support is compiled into <TT>ntpdate</TT>, then the -<TT>server</TT> argument is optional if <TT>ntpdate</TT> can find a time -server in the NetInfo configuration for <TT>ntpd</TT>. - -<H4> -Command Line Options</H4> - -<DL> -<DT> -<TT>-a <I>key</I></TT></DT> - -<DD> -Enable the authentication function and specify the key identifier to be -used for authentication as the argument <I>key</I><TT>ntpdate</TT>. The -keys and key identifiers must match in both the client and server key files. -The default is to disable the authentication function.</DD> - -<DT> -<TT>-B</TT></DT> - -<DD> -Force the time to always be slewed using the adjtime() system call, even -if the measured offset is greater than +-128 ms. The default is to step -the time using settimeofday() if the offset is greater than +-128 ms. Note -that, if the offset is much greater than +-128 ms in this case, that it -can take a long time (hours) to slew the clock to the correct value. During -this time. the host should not be used to synchronize clients.</DD> - -<DT> -<TT>-b</TT></DT> - -<DD> -Force the time to be stepped using the settimeofday() system call, rather -than slewed (default) using the adjtime() system call. This option should -be used when called from a startup file at boot time.</DD> - -<DT> -<TT>-d</TT></DT> - -<DD> -Enable the debugging mode, in which <TT>ntpdate</TT> will go through all -the steps, but not adjust the local clock. Information useful for general -debugging will also be printed.</DD> - -<DT> -<TT>-e <I>authdelay</I></TT></DT> - -<DD> -Specify the processing delay to perform an authentication function as the -value <I>authdelay</I>, in seconds and fraction (see <TT>ntpd</TT> for -details). This number is usually small enough to be negligible for most -purposes, though specifying a value may improve timekeeping on very slow -CPU's.</DD> - -<DT> -<TT>-k <I>keyfile</I></TT></DT> - -<DD> -Specify the path for the authentication key file as the string <I>keyfile</I>. -The default is <TT>/etc/ntp.keys</TT>. This file should be in the format -described in <TT>ntpd</TT>.</DD> - -<DT> -<TT>-o <I>version</I></TT></DT> - -<DD> -Specify the NTP version for outgoint packets as the integer <I>version</I>, -which can be 1 or 2. The default is 3. This allows <TT>ntpdate</TT> to -be used with older NTP versions.</DD> - -<DT> -<TT>-p <I>samples</I></TT></DT> - -<DD> -Specify the number of samples to be acquired from each server as the integer -<I>samples</I>, with values from 1 to 8 inclusive. The default is 4.</DD> - -<DT> -<I><TT>-q</TT></I></DT> - -<DD> -Query only - don't set the clock.</DD> - -<DT> -<TT>-s</TT></DT> - -<DD> -Divert logging output from the standard output (default) to the system -<TT>syslog</TT> facility. This is designed primarily for convenience of -<TT>cron</TT> scripts.</DD> - -<DT> -<TT>-t <I>timeout</I></TT></DT> - -<DD> -Specify the maximum time waiting for a server response as the value <I>timeout</I>, -in seconds and fraction. The value is is rounded to a multiple of 0.2 seconds. -The default is 1 second, a value suitable for polling across a LAN.</DD> - -<DT> -<TT>-u</TT></DT> - -<DD> -Direct <TT>ntpdate</TT> to use an unprivileged port or outgoing packets. -This is most useful when behind a firewall that blocks incoming traffic -to privileged ports, and you want to synchronise with hosts beyond the -firewall. Note that the <TT>-d</TT> option always uses unprivileged ports.</DD> - -<DT> -<TT>-<I>v</I></TT></DT> - -<DD> -Be verbose. This option will cause <TT>ntpdate</TT>'s version identification -string to be logged.</DD> -</DL> - -<H4> -Files</H4> -<TT>/etc/ntp.keys</TT> - encryption keys used by <TT>ntpdate</TT>. -<H4> -Bugs</H4> -The slew adjustment is actually 50% larger than the measured offset, since -this (it is argued) will tend to keep a badly drifting clock more accurate. -This is probably not a good idea and may cause a troubling hunt for some -values of the kernel variables <TT>tick</TT> and <TT>tickadj</TT>. -<HR> -<ADDRESS> -David L. Mills (mills@udel.edu)</ADDRESS> - -</BODY> -</HTML> +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> +<html> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org"> +<title>ntpdate - set the date and time via NTP</title> +</head> +<body> +<h3><tt>ntpdate</tt> - set the date and time via NTP</h3> + +<img align="left" src="pic/rabbit.gif" alt="gif"><a href= +"http://www.eecis.udel.edu/~mills/pictures.htm">from <i>Alice's +Adventures in Wonderland</i>, Lewis Carroll</a> + +<p>I told you it was eyeball and wristwatch.<br clear="left"> +</p> + +<hr> +<p>Disclaimer: The functionality of this program is now available +in the <tt>ntpd</tt> program. See the <tt>-q</tt> command line +option in the <a href="ntpd.htm"><tt>ntpd</tt> - Network Time +Protocol (NTP) daemon</a> page. After a suitable period of +mourning, the <tt>ntpdate</tt> program is to be retired from this +distribution</p> + +<h4>Synopsis</h4> + +<tt>ntpdate [ -bBdoqsuv ] [ -a <i>key</i> ] [ -e <i>authdelay</i> ] +[ -k <i>keyfile</i> ] [ -o <i>version</i> ] [ -p <i>samples</i> ] [ +-t <i>timeout</i> ] <i>server</i> [ ... ]</tt> + +<h4>Description</h4> + +<tt>ntpdate</tt> sets the local date and time by polling the +Network Time Protocol (NTP) server(s) given as the <i>server</i> +arguments to determine the correct time. It must be run as root on +the local host. A number of samples are obtained from each of the +servers specified and a subset of the NTP clock filter and +selection algorithms are applied to select the best of these. Note +that the accuracy and reliability of <tt>ntpdate</tt> depends on +the number of servers, the number of polls each time it is run and +the interval between runs. + +<p><tt>ntpdate</tt> can be run manually as necessary to set the +host clock, or it can be run from the host startup script to set +the clock at boot time. This is useful in some cases to set the +clock initially before starting the NTP daemon <tt>ntpd</tt>. It is +also possible to run <tt>ntpdate</tt> from a <tt>cron</tt> script. +However, it is important to note that <tt>ntpdate</tt> with +contrived <tt>cron</tt> scripts is no substitute for the NTP +daemon, which uses sophisticated algorithms to maximize accuracy +and reliability while minimizing resource use. Finally, since <tt> +ntpdate</tt> does not discipline the host clock frequency as does +<tt>ntpd</tt>, the accuracy using <tt>ntpdate</tt> is limited.</p> + +<p>Time adjustments are made by <tt>ntpdate</tt> in one of two +ways. If <tt>ntpdate</tt> determines the clock is in error more +than 0.5 second it will simply step the time by calling the system +<tt>settimeofday()</tt> routine. If the error is less than 0.5 +seconds, it will slew the time by calling the system <tt> +adjtime()</tt> routine. The latter technique is less disruptive and +more accurate when the error is small, and works quite well when +<tt>ntpdate</tt> is run by <tt>cron</tt> every hour or two.</p> + +<p><tt>ntpdate</tt> will decline to set the date if an NTP server +daemon (e.g., <tt>ntpd</tt>) is running on the same host. When +running <tt>ntpdate</tt> on a regular basis from <tt>cron</tt> as +an alternative to running a daemon, doing so once every hour or two +will result in precise enough timekeeping to avoid stepping the +clock.</p> + +<p>If NetInfo support is compiled into <tt>ntpdate</tt>, then the +<tt>server</tt> argument is optional if <tt>ntpdate</tt> can find a +time server in the NetInfo configuration for <tt>ntpd</tt>.</p> + +<h4>Command Line Options</h4> + +<dl> +<dt><tt>-a <i>key</i></tt></dt> + +<dd>Enable the authentication function and specify the key +identifier to be used for authentication as the argument <i> +key</i><tt>ntpdate</tt>. The keys and key identifiers must match in +both the client and server key files. The default is to disable the +authentication function.</dd> + +<dt><tt>-B</tt></dt> + +<dd>Force the time to always be slewed using the adjtime() system +call, even if the measured offset is greater than +-128 ms. The +default is to step the time using settimeofday() if the offset is +greater than +-128 ms. Note that, if the offset is much greater +than +-128 ms in this case, that it can take a long time (hours) to +slew the clock to the correct value. During this time. the host +should not be used to synchronize clients.</dd> + +<dt><tt>-b</tt></dt> + +<dd>Force the time to be stepped using the settimeofday() system +call, rather than slewed (default) using the adjtime() system call. +This option should be used when called from a startup file at boot +time.</dd> + +<dt><tt>-d</tt></dt> + +<dd>Enable the debugging mode, in which <tt>ntpdate</tt> will go +through all the steps, but not adjust the local clock. Information +useful for general debugging will also be printed.</dd> + +<dt><tt>-e <i>authdelay</i></tt></dt> + +<dd>Specify the processing delay to perform an authentication +function as the value <i>authdelay</i>, in seconds and fraction +(see <tt>ntpd</tt> for details). This number is usually small +enough to be negligible for most purposes, though specifying a +value may improve timekeeping on very slow CPU's.</dd> + +<dt><tt>-k <i>keyfile</i></tt></dt> + +<dd>Specify the path for the authentication key file as the string +<i>keyfile</i>. The default is <tt>/etc/ntp.keys</tt>. This file +should be in the format described in <tt>ntpd</tt>.</dd> + +<dt><tt>-o <i>version</i></tt></dt> + +<dd>Specify the NTP version for outgoint packets as the integer <i> +version</i>, which can be 1 or 2. The default is 3. This allows +<tt>ntpdate</tt> to be used with older NTP versions.</dd> + +<dt><tt>-p <i>samples</i></tt></dt> + +<dd>Specify the number of samples to be acquired from each server +as the integer <i>samples</i>, with values from 1 to 8 inclusive. +The default is 4.</dd> + +<dt><i><tt>-q</tt></i></dt> + +<dd>Query only - don't set the clock.</dd> + +<dt><tt>-s</tt></dt> + +<dd>Divert logging output from the standard output (default) to the +system <tt>syslog</tt> facility. This is designed primarily for +convenience of <tt>cron</tt> scripts.</dd> + +<dt><tt>-t <i>timeout</i></tt></dt> + +<dd>Specify the maximum time waiting for a server response as the +value <i>timeout</i>, in seconds and fraction. The value is is +rounded to a multiple of 0.2 seconds. The default is 1 second, a +value suitable for polling across a LAN.</dd> + +<dt><tt>-u</tt></dt> + +<dd>Direct <tt>ntpdate</tt> to use an unprivileged port or outgoing +packets. This is most useful when behind a firewall that blocks +incoming traffic to privileged ports, and you want to synchronise +with hosts beyond the firewall. Note that the <tt>-d</tt> option +always uses unprivileged ports.</dd> + +<dt><tt>-<i>v</i></tt></dt> + +<dd>Be verbose. This option will cause <tt>ntpdate</tt>'s version +identification string to be logged.</dd> +</dl> + +<h4>Files</h4> + +<tt>/etc/ntp.keys</tt> - encryption keys used by <tt>ntpdate</tt>. + +<h4>Bugs</h4> + +The slew adjustment is actually 50% larger than the measured +offset, since this (it is argued) will tend to keep a badly +drifting clock more accurate. This is probably not a good idea and +may cause a troubling hunt for some values of the kernel variables +<tt>tick</tt> and <tt>tickadj</tt>. + +<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 +<mills@udel.edu></a></address> +</body> +</html> + |
