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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0"
xml:id="man.clockdiff">
<refentryinfo>
<title>clockdiff</title>
<productname>iputils</productname>
</refentryinfo>
<refmeta>
<refentrytitle>
<application>clockdiff</application>
</refentrytitle>
<manvolnum>8</manvolnum>
<refmiscinfo class='manual'>iputils</refmiscinfo>
</refmeta>
<refnamediv>
<refname>clockdiff</refname>
<refpurpose>measure clock difference between hosts</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis sepchar=" ">
<command>clockdiff</command>
<arg choice="opt" rep="norepeat">
<option>-o</option>
</arg>
<arg choice="opt" rep="norepeat">
<option>-o1</option>
</arg>
<arg choice="opt" rep="norepeat">
<option>--time-format
<replaceable>ctime iso</replaceable></option>
</arg>
<arg choice="opt" rep="norepeat">
<option>-V</option>
</arg>
<arg choice="req" rep="norepeat">destination</arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsection xml:id="description">
<info>
<title>DESCRIPTION</title>
</info>
<para>
<command>clockdiff</command> Measures clock difference between
us and
<emphasis remap="I">destination</emphasis> with 1 msec
resolution using ICMP TIMESTAMP [2] packets or, optionally, IP
TIMESTAMP option [3] added to ICMP ECHO. [1]</para>
</refsection>
<refsection xml:id="options">
<info>
<title>OPTIONS</title>
</info>
<variablelist remap='TP'>
<varlistentry>
<term>
<option>-o</option>
</term>
<listitem>
<para>Use IP TIMESTAMP with ICMP ECHO instead of ICMP
TIMESTAMP messages. It is useful with some destinations,
which do not support ICMP TIMESTAMP (f.e. Solaris
<2.4).</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-o1</option>
</term>
<listitem>
<para>Slightly different form of
<option>-o</option>, namely it uses three-term IP
TIMESTAMP with prespecified hop addresses instead of four
term one. What flavor works better depends on target
host. Particularly,
<option>-o</option> is better for Linux.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-T</option>
</term>
<term>
<option>--time-format <replaceable>ctime iso</replaceable></option>
</term>
<listitem>
<para>Print time stamp in output either ISO-8601 format or
classical ctime format. The ctime format is default. The ISO
time stamp includes timezone, and is easier to parse.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-I</option>
</term>
<listitem>
<para>Alias of <option>--time-format <replaceable>iso</replaceable>
</option> option and argument.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-h</option>
</term>
<term>
<option>--help</option>
</term>
<listitem>
<para>Print help and exit.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-V</option>
</term>
<term>
<option>--version</option>
</term>
<listitem>
<para>Print version and exit.</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection xml:id="warnings">
<info>
<title>WARNINGS</title>
</info>
<variablelist remap="TP">
<varlistentry>
<listitem>
<para>• Some nodes (Cisco) use non-standard timestamps,
which is allowed by RFC, but makes timestamps mostly
useless.</para>
</listitem>
</varlistentry>
<varlistentry>
<listitem>
<para>• Some nodes generate messed timestamps
(Solaris>2.4), when run
<command>xntpd</command>. Seems, its IP stack uses a
corrupted clock source, which is synchronized to
time-of-day clock periodically and jumps randomly making
timestamps mostly useless. Good news is that you can use
NTP in this case, which is even better.</para>
</listitem>
</varlistentry>
<varlistentry>
<listitem>
<para>•
<command>clockdiff</command> shows difference in time
modulo 24 days.</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsect1 id='see_also'>
<title>SEE ALSO</title>
<para>
<citerefentry>
<refentrytitle>ping</refentrytitle>
<manvolnum>8</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>arping</refentrytitle>
<manvolnum>8</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>tracepath</refentrytitle>
<manvolnum>8</manvolnum>
</citerefentry>.</para>
</refsect1>
<refsection xml:id="references">
<info>
<title>REFERENCES</title>
</info>
<para>[1] ICMP ECHO, RFC0792, page 14.</para>
<para>[2] ICMP TIMESTAMP, RFC0792, page 16.</para>
<para>[3] IP TIMESTAMP option, RFC0791, 3.1, page 16.</para>
</refsection>
<refsect1 id='author'>
<title>AUTHOR</title>
<para>
<command>clockdiff</command> was compiled by Alexey Kuznetsov
<kuznet@ms2.inr.ac.ru>. It was based on code borrowed
from BSD
<command>timed</command> daemon.</para>
</refsect1>
<refsect1 id='security'>
<title>SECURITY</title>
<para>
<command>clockdiff</command> requires CAP_NET_RAW and
CAP_SYS_NICE capabilities to be executed. It is safe
to be used as set-uid root.</para>
</refsect1>
<refsect1 id='availability'>
<title>AVAILABILITY</title>
<para>
<command>clockdiff</command> is part of
<emphasis remap='I'>iputils</emphasis> package.</para>
</refsect1>
</refentry>
|
