svn commit: r43711 - head/en_US.ISO8859-1/books/handbook/network-servers
Dru Lavigne
dru at FreeBSD.org
Fri Jan 31 21:54:19 UTC 2014
Author: dru
Date: Fri Jan 31 21:54:18 2014
New Revision: 43711
URL: http://svnweb.freebsd.org/changeset/doc/43711
Log:
White space fix only. Translators can ignore.
Sponsored by: iXsystems
Modified:
head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml
Modified: head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml
==============================================================================
--- head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml Fri Jan 31 21:35:11 2014 (r43710)
+++ head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml Fri Jan 31 21:54:18 2014 (r43711)
@@ -5228,39 +5228,38 @@ Starting smbd.</screen>
<title>Clock Synchronization with NTP</title>
<indexterm><primary>NTP</primary>
- <secondary>ntpd</secondary>
+ <secondary>ntpd</secondary>
</indexterm>
- <para>Over time, a computer's clock is prone to drift. This is
- problematic as many network services require the computers on a network
- to share the same accurate time. Accurate time is also needed to ensure
- that file timestamps stay
- consistent. The
- Network Time Protocol (<acronym>NTP</acronym>) is one way to provide clock
- accuracy in a network.</para>
-
- <para>&os; includes &man.ntpd.8;
- which can be configured to query other
- <acronym>NTP</acronym> servers in order to
- synchronize the clock on that machine or to provide time services to
- other computers in the network. The servers which are queried
- can be local to the network or provided by an <acronym>ISP</acronym>.
- In addition, an <link
- xlink:href="http://support.ntp.org/bin/view/Servers/WebHome">online
- list of publicly accessible <acronym>NTP</acronym> servers</link>
- is available. When choosing a public <acronym>NTP</acronym> server, select
- one that is geographically close and
- review its usage policy.</para>
-
- <para>Choosing several <acronym>NTP</acronym> servers is recommended in
- case one of the servers becomes unreachable or
- its clock proves unreliable. As <application>ntpd</application> receives responses,
- it favors
- reliable servers over the less reliable ones.</para>
-
- <para>This section describes how to configure <application>ntpd</application> on &os;. Further documentation can be found in
- <filename>/usr/share/doc/ntp/</filename> in HTML
- format.</para>
+ <para>Over time, a computer's clock is prone to drift. This is
+ problematic as many network services require the computers on a
+ network to share the same accurate time. Accurate time is also
+ needed to ensure that file timestamps stay consistent. The
+ Network Time Protocol (<acronym>NTP</acronym>) is one way to
+ provide clock accuracy in a network.</para>
+
+ <para>&os; includes &man.ntpd.8; which can be configured to query
+ other <acronym>NTP</acronym> servers in order to synchronize the
+ clock on that machine or to provide time services to other
+ computers in the network. The servers which are queried can be
+ local to the network or provided by an <acronym>ISP</acronym>.
+ In addition, an <link
+ xlink:href="http://support.ntp.org/bin/view/Servers/WebHome">online
+ list of publicly accessible <acronym>NTP</acronym>
+ servers</link> is available. When choosing a public
+ <acronym>NTP</acronym> server, select one that is geographically
+ close and review its usage policy.</para>
+
+ <para>Choosing several <acronym>NTP</acronym> servers is
+ recommended in case one of the servers becomes unreachable or
+ its clock proves unreliable. As <application>ntpd</application>
+ receives responses, it favors reliable servers over the less
+ reliable ones.</para>
+
+ <para>This section describes how to configure
+ <application>ntpd</application> on &os;. Further documentation
+ can be found in <filename>/usr/share/doc/ntp/</filename> in HTML
+ format.</para>
<sect2>
<title><acronym>NTP</acronym> Configuration</title>
@@ -5270,115 +5269,117 @@ Starting smbd.</screen>
<tertiary>ntpdate</tertiary>
</indexterm>
- <para>To only synchronize the clock when a system boots,
- use &man.ntpdate.8;. This alone can be appropriate for
- desktops which are frequently rebooted. However,
- most systems should
- run <application>ntpdate</application> at boot time as well as configure <application>ntpd</application>.
- This is because <application>ntpd</application>
- changes the clock gradually, whereas <application>ntpdate</application>
- sets the clock, no matter how great the difference between a
- machine's current clock setting and the correct time.</para>
-
- <para>To enable <application>ntpdate</application> at boot time, add
- <literal>ntpdate_enable="YES"</literal> to
- <filename>/etc/rc.conf</filename>. To also enable
- <application>ntpd</application>, add the <literal>ntpd_enable="YES"</literal>
- entry to <filename>/etc/rc.conf</filename>. Additional variables can be specified
- in <filename>/etc/rc.conf</filename>. Refer to &man.rc.conf.5;,
- &man.ntpdate.8;, and &man.ntpd.8; for details.</para>
-
- <para>Both applications
- read <filename>/etc/ntp.conf</filename> to determine
- which servers to query. Here is a simple example of an
- <filename>/etc/ntp.conf</filename>:</para>
+ <para>To only synchronize the clock when a system boots, use
+ &man.ntpdate.8;. This alone can be appropriate for desktops
+ which are frequently rebooted. However, most systems should
+ run <application>ntpdate</application> at boot time as well as
+ configure <application>ntpd</application>. This is because
+ <application>ntpd</application> changes the clock gradually,
+ whereas <application>ntpdate</application> sets the clock, no
+ matter how great the difference between a machine's current
+ clock setting and the correct time.</para>
+
+ <para>To enable <application>ntpdate</application> at boot time,
+ add <literal>ntpdate_enable="YES"</literal> to
+ <filename>/etc/rc.conf</filename>. To also enable
+ <application>ntpd</application>, add the
+ <literal>ntpd_enable="YES"</literal> entry to
+ <filename>/etc/rc.conf</filename>. Additional variables can
+ be specified in <filename>/etc/rc.conf</filename>. Refer to
+ &man.rc.conf.5;, &man.ntpdate.8;, and &man.ntpd.8; for
+ details.</para>
+
+ <para>Both applications read <filename>/etc/ntp.conf</filename>
+ to determine which servers to query. Here is a simple example
+ of an <filename>/etc/ntp.conf</filename>:</para>
- <example>
- <title> Sample <filename>/etc/ntp.conf</filename></title>
+ <example>
+ <title> Sample <filename>/etc/ntp.conf</filename></title>
<programlisting>server ntplocal.example.com prefer
server timeserver.example.org
server ntp2a.example.net
driftfile /var/db/ntp.drift</programlisting>
- </example>
+ </example>
- <para>The format of this file is
- described in &man.ntp.conf.5;. The <literal>server</literal> option specifies which
- servers to query, with one server listed on each line.
- If a server entry includes <literal>prefer</literal>,
- that server is preferred over other servers. A response
- from a preferred server will be discarded if it differs
- significantly from responses; otherwise it
- will be used.
- The <literal>prefer</literal> argument should only be used for
- <acronym>NTP</acronym> servers that are known to be highly accurate, such as
- those with special time monitoring hardware.</para>
-
- <para>The <literal>driftfile</literal> entry specifies which
- file is used to store the system clock's frequency offset.
- <application>ntpd</application> uses this to automatically
- compensate for the clock's natural drift, allowing it to
- maintain a reasonably correct setting even if it is cut off
- from all external time sources for a period of time. This
- file also stores information about previous responses
- from <acronym>NTP</acronym> servers. Since this file contains
- internal information for <acronym>NTP</acronym>, it should not be modified.</para>
-
- <para>By default, an <acronym>NTP</acronym> server is accessible to any
- network host. The <literal>restrict</literal>
- option in <filename>/etc/ntp.conf</filename> can be used to
- control which systems can access the server. For example,
- to deny all machines from accessing the <acronym>NTP</acronym>
- server, add the following line to
- <filename>/etc/ntp.conf</filename>:</para>
+ <para>The format of this file is described in &man.ntp.conf.5;.
+ The <literal>server</literal> option specifies which servers
+ to query, with one server listed on each line. If a server
+ entry includes <literal>prefer</literal>, that server is
+ preferred over other servers. A response from a preferred
+ server will be discarded if it differs significantly from
+ responses; otherwise it will be used. The
+ <literal>prefer</literal> argument should only be used for
+ <acronym>NTP</acronym> servers that are known to be highly
+ accurate, such as those with special time monitoring
+ hardware.</para>
+
+ <para>The <literal>driftfile</literal> entry specifies which
+ file is used to store the system clock's frequency offset.
+ <application>ntpd</application> uses this to automatically
+ compensate for the clock's natural drift, allowing it to
+ maintain a reasonably correct setting even if it is cut off
+ from all external time sources for a period of time. This
+ file also stores information about previous responses
+ from <acronym>NTP</acronym> servers. Since this file contains
+ internal information for <acronym>NTP</acronym>, it should not
+ be modified.</para>
+
+ <para>By default, an <acronym>NTP</acronym> server is accessible
+ to any network host. The <literal>restrict</literal> option
+ in <filename>/etc/ntp.conf</filename> can be used to control
+ which systems can access the server. For example, to deny all
+ machines from accessing the <acronym>NTP</acronym> server, add
+ the following line to
+ <filename>/etc/ntp.conf</filename>:</para>
- <programlisting>restrict default ignore</programlisting>
+ <programlisting>restrict default ignore</programlisting>
<note>
- <para>This will also prevent access from other <acronym>NTP</acronym> servers.
- If there is a
- need to synchronize with an external <acronym>NTP</acronym>
+ <para>This will also prevent access from other
+ <acronym>NTP</acronym> servers. If there is a need to
+ synchronize with an external <acronym>NTP</acronym>
server, allow only that specific server. Refer to
&man.ntp.conf.5; for more information.</para>
</note>
- <para>To allow machines within the network to synchronize
- their clocks with the server, but ensure they are not
- allowed to configure the server or be used as peers to
- synchronize against, instead use:</para>
-
- <programlisting>restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap</programlisting>
-
- <para>where
- <systemitem class="ipaddress">192.168.1.0</systemitem> is the
- local network address and
- <systemitem class="netmask">255.255.255.0</systemitem> is
- the network's subnet mask.</para>
-
- <para>Multiple <literal>restrict</literal> entries are supported.
- For more
- details, refer to the <literal>Access Control Support</literal>
- subsection of &man.ntp.conf.5;.</para>
-
- <para>Once
- <literal>ntpd_enable="YES"</literal> has been added to
- <filename>/etc/rc.conf</filename>, <application>ntpd</application>
- can be started now without rebooting the system by typing:</para>
+ <para>To allow machines within the network to synchronize their
+ clocks with the server, but ensure they are not allowed to
+ configure the server or be used as peers to synchronize
+ against, instead use:</para>
+
+ <programlisting>restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap</programlisting>
+
+ <para>where <systemitem
+ class="ipaddress">192.168.1.0</systemitem> is the local
+ network address and <systemitem
+ class="netmask">255.255.255.0</systemitem> is the network's
+ subnet mask.</para>
+
+ <para>Multiple <literal>restrict</literal> entries are
+ supported. For more details, refer to the <literal>Access
+ Control Support</literal> subsection of
+ &man.ntp.conf.5;.</para>
+
+ <para>Once <literal>ntpd_enable="YES"</literal> has been added
+ to <filename>/etc/rc.conf</filename>,
+ <application>ntpd</application> can be started now without
+ rebooting the system by typing:</para>
<screen>&prompt.root; <userinput>service ntpd start</userinput></screen>
</sect2>
<sect2>
- <title>Using <acronym>NTP</acronym> with a <acronym>PPP</acronym>
- Connection</title>
+ <title>Using <acronym>NTP</acronym> with a
+ <acronym>PPP</acronym> Connection</title>
<para><application>ntpd</application> does not need a permanent
connection to the Internet to function properly. However, if
a <acronym>PPP</acronym> connection is configured to dial out
- on demand, <acronym>NTP</acronym> traffic should be prevented from
- triggering a dial out or keeping the connection alive. This can be configured
- with <literal>filter</literal>
+ on demand, <acronym>NTP</acronym> traffic should be prevented
+ from triggering a dial out or keeping the connection alive.
+ This can be configured with <literal>filter</literal>
directives in <filename>/etc/ppp/ppp.conf</filename>. For
example:</para>
@@ -5398,8 +5399,8 @@ driftfile /var/db/ntp.drift</programlist
<note>
<para>Some Internet access providers block low-numbered ports,
- preventing NTP from functioning since replies never
- reach the machine.</para>
+ preventing NTP from functioning since replies never reach
+ the machine.</para>
</note>
</sect2>
</sect1>
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