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<title>Chapter�3.�Name Server Configuration</title>
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<tr><th colspan="3" align="center">Chapter�3.�Name Server Configuration</th></tr>
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<div class="chapter" lang="en">
<div class="titlepage"><div><div><h2 class="title">
<div class="toc">
<p><b>Table of Contents</b></p>
<dl>
<dt><span class="sect1"><a href="Bv9ARM.ch03.html#sample_configuration">Sample Configurations</a></span></dt>
<dd><dl>
<dt><span class="sect2"><a href="Bv9ARM.ch03.html#id2548733">A Caching-only Name Server</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch03.html#id2548749">An Authoritative-only Name Server</a></span></dt>
</dl></dd>
<dd><dl>
<dt><span class="sect2"><a href="Bv9ARM.ch03.html#id2549269">Tools for Use With the Name Server Daemon</a></span></dt>
</dl></dd>
</dl>
</div>
<p>
In this section we provide some suggested configurations along
with guidelines for their use. We suggest reasonable values for
certain option settings.
</p>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sample_configuration"></a>Sample Configurations</h2></div></div></div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2548733"></a>A Caching-only Name Server</h3></div></div></div>
<p>
The following sample configuration is appropriate for a caching-only
name server for use by clients internal to a corporation. All
queries
from outside clients are refused using the <span><strong class="command">allow-query</strong></span>
option. Alternatively, the same effect could be achieved using
suitable
firewall rules.
</p>
<pre class="programlisting">
// Two corporate subnets we wish to allow queries from.
options {
allow-query { corpnets; };
};
// Provide a reverse mapping for the loopback address 127.0.0.1
zone "0.0.127.in-addr.arpa" {
type master;
file "localhost.rev";
notify no;
};
</pre>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2548749"></a>An Authoritative-only Name Server</h3></div></div></div>
<p>
This sample configuration is for an authoritative-only server
</p>
<pre class="programlisting">
options {
allow-query-cache { none; }; // Do not allow access to cache
allow-query { any; }; // This is the default
recursion no; // Do not provide recursive service
};
// Provide a reverse mapping for the loopback address 127.0.0.1
zone "0.0.127.in-addr.arpa" {
type master;
file "localhost.rev";
notify no;
};
// We are the master server for example.com
zone "example.com" {
type master;
file "example.com.db";
// IP addresses of slave servers allowed to transfer example.com
allow-transfer {
192.168.4.14;
192.168.5.53;
};
};
// We are a slave server for eng.example.com
zone "eng.example.com" {
type slave;
file "eng.example.com.bk";
// IP address of eng.example.com master server
masters { 192.168.4.12; };
};
</pre>
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2548772"></a>Load Balancing</h2></div></div></div>
<p>
A primitive form of load balancing can be achieved in
the <span class="acronym">DNS</span> by using multiple A records for
one name.
</p>
<p>
For example, if you have three WWW servers with network addresses
of 10.0.0.1, 10.0.0.2 and 10.0.0.3, a set of records such as the
following means that clients will connect to each machine one third
of the time:
</p>
<div class="informaltable"><table border="1">
<colgroup>
<col>
<col>
<col>
<col>
<col>
</colgroup>
<tbody>
<tr>
<td>
<p>
Name
</p>
</td>
<td>
<p>
TTL
</p>
</td>
<td>
<p>
CLASS
</p>
</td>
<td>
<p>
TYPE
</p>
</td>
<td>
<p>
Resource Record (RR) Data
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="literal">www</code>
</p>
</td>
<td>
<p>
<code class="literal">600</code>
</p>
</td>
<td>
<p>
<code class="literal">IN</code>
</p>
</td>
<td>
<p>
<code class="literal">A</code>
</p>
</td>
<td>
<p>
<code class="literal">10.0.0.1</code>
</p>
</td>
</tr>
<tr>
<td>
<p></p>
</td>
<td>
<p>
<code class="literal">600</code>
</p>
</td>
<td>
<p>
<code class="literal">IN</code>
</p>
</td>
<td>
<p>
<code class="literal">A</code>
</p>
</td>
<td>
<p>
<code class="literal">10.0.0.2</code>
</p>
</td>
</tr>
<tr>
<td>
<p></p>
</td>
<td>
<p>
<code class="literal">600</code>
</p>
</td>
<td>
<p>
<code class="literal">IN</code>
</p>
</td>
<td>
<p>
<code class="literal">A</code>
</p>
</td>
<td>
<p>
<code class="literal">10.0.0.3</code>
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
When a resolver queries for these records, <span class="acronym">BIND</span> will rotate
them and respond to the query with the records in a different
order. In the example above, clients will randomly receive
records in the order 1, 2, 3; 2, 3, 1; and 3, 1, 2. Most clients
will use the first record returned and discard the rest.
</p>
<p>
For more detail on ordering responses, check the
<span><strong class="command">rrset-order</strong></span> substatement in the
<span><strong class="command">options</strong></span> statement, see
</p>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2549264"></a>Name Server Operations</h2></div></div></div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2549269"></a>Tools for Use With the Name Server Daemon</h3></div></div></div>
<p>
This section describes several indispensable diagnostic,
administrative and monitoring tools available to the system
administrator for controlling and debugging the name server
daemon.
</p>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="diagnostic_tools"></a>Diagnostic Tools</h4></div></div></div>
<p>
The <span><strong class="command">dig</strong></span>, <span><strong class="command">host</strong></span>, and
<span><strong class="command">nslookup</strong></span> programs are all command
line tools
for manually querying name servers. They differ in style and
output format.
</p>
<div class="variablelist"><dl>
<dt><span class="term"><a name="dig"></a><span><strong class="command">dig</strong></span></span></dt>
<dd>
<p>
The domain information groper (<span><strong class="command">dig</strong></span>)
is the most versatile and complete of these lookup tools.
It has two modes: simple interactive
mode for a single query, and batch mode which executes a
query for
each in a list of several query lines. All query options are
accessible
from the command line.
</p>
<div class="cmdsynopsis"><p><code class="command">dig</code> [@<em class="replaceable"><code>server</code></em>] <em class="replaceable"><code>domain</code></em> [<em class="replaceable"><code>query-type</code></em>] [<em class="replaceable"><code>query-class</code></em>] [+<em class="replaceable"><code>query-option</code></em>] [-<em class="replaceable"><code>dig-option</code></em>] [%<em class="replaceable"><code>comment</code></em>]</p></div>
<p>
The usual simple use of dig will take the form
</p>
<p>
<span><strong class="command">dig @server domain query-type query-class</strong></span>
</p>
<p>
For more information and a list of available commands and
options, see the <span><strong class="command">dig</strong></span> man
page.
</p>
</dd>
<dt><span class="term"><span><strong class="command">host</strong></span></span></dt>
<dd>
<p>
The <span><strong class="command">host</strong></span> utility emphasizes
simplicity
and ease of use. By default, it converts
between host names and Internet addresses, but its
functionality
can be extended with the use of options.
</p>
<div class="cmdsynopsis"><p><code class="command">host</code> [-aCdlrTwv] [-c <em class="replaceable"><code>class</code></em>] [-N <em class="replaceable"><code>ndots</code></em>] [-t <em class="replaceable"><code>type</code></em>] [-W <em class="replaceable"><code>timeout</code></em>] [-R <em class="replaceable"><code>retries</code></em>] <em class="replaceable"><code>hostname</code></em> [<em class="replaceable"><code>server</code></em>]</p></div>
<p>
For more information and a list of available commands and
options, see the <span><strong class="command">host</strong></span> man
page.
</p>
</dd>
<dt><span class="term"><span><strong class="command">nslookup</strong></span></span></dt>
<dd>
<p><span><strong class="command">nslookup</strong></span>
has two modes: interactive and
non-interactive. Interactive mode allows the user to
query name servers for information about various
hosts and domains or to print a list of hosts in a
domain. Non-interactive mode is used to print just
the name and requested information for a host or
domain.
</p>
<div class="cmdsynopsis"><p><code class="command">nslookup</code> [-option...] [[<em class="replaceable"><code>host-to-find</code></em>] | [- [server]]]</p></div>
<p>
Interactive mode is entered when no arguments are given (the
default name server will be used) or when the first argument
is a
hyphen (`-') and the second argument is the host name or
Internet address
of a name server.
</p>
<p>
Non-interactive mode is used when the name or Internet
address
of the host to be looked up is given as the first argument.
The
optional second argument specifies the host name or address
of a name server.
</p>
<p>
Due to its arcane user interface and frequently inconsistent
behavior, we do not recommend the use of <span><strong class="command">nslookup</strong></span>.
Use <span><strong class="command">dig</strong></span> instead.
</p>
</dd>
</dl></div>
</div>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="admin_tools"></a>Administrative Tools</h4></div></div></div>
<p>
Administrative tools play an integral part in the management
of a server.
</p>
<div class="variablelist"><dl>
<dt>
<a name="named-checkconf"></a><span class="term"><span><strong class="command">named-checkconf</strong></span></span>
</dt>
<dd>
<p>
The <span><strong class="command">named-checkconf</strong></span> program
</p>
<div class="cmdsynopsis"><p><code class="command">named-checkconf</code> [-jvz] [-t <em class="replaceable"><code>directory</code></em>] [<em class="replaceable"><code>filename</code></em>]</p></div>
</dd>
<dt>
<a name="named-checkzone"></a><span class="term"><span><strong class="command">named-checkzone</strong></span></span>
</dt>
<dd>
<p>
The <span><strong class="command">named-checkzone</strong></span> program
checks a master file for
syntax and consistency.
</p>
<div class="cmdsynopsis"><p><code class="command">named-checkzone</code> [-djqvD] [-c <em class="replaceable"><code>class</code></em>] [-o <em class="replaceable"><code>output</code></em>] [-t <em class="replaceable"><code>directory</code></em>] [-w <em class="replaceable"><code>directory</code></em>] [-k <em class="replaceable"><code>(ignore|warn|fail)</code></em>] [-n <em class="replaceable"><code>(ignore|warn|fail)</code></em>] [-W <em class="replaceable"><code>(ignore|warn)</code></em>] <em class="replaceable"><code>zone</code></em> [<em class="replaceable"><code>filename</code></em>]</p></div>
</dd>
<dt>
<a name="named-compilezone"></a><span class="term"><span><strong class="command">named-compilezone</strong></span></span>
</dt>
<dd><p>
Similar to <span><strong class="command">named-checkzone,</strong></span> but
it always dumps the zone content to a specified file
(typically in a different format).
</p></dd>
<dt>
<a name="rndc"></a><span class="term"><span><strong class="command">rndc</strong></span></span>
</dt>
<dd>
<p>
The remote name daemon control
(<span><strong class="command">rndc</strong></span>) program allows the
system
administrator to control the operation of a name server.
If you run <span><strong class="command">rndc</strong></span> without any
options
it will display a usage message as follows:
</p>
<div class="cmdsynopsis"><p><code class="command">rndc</code> [-c <em class="replaceable"><code>config</code></em>] [-s <em class="replaceable"><code>server</code></em>] [-p <em class="replaceable"><code>port</code></em>] [-y <em class="replaceable"><code>key</code></em>] <em class="replaceable"><code>command</code></em> [<em class="replaceable"><code>command</code></em>...]</p></div>
<p>The <span><strong class="command">command</strong></span>
is one of the following:
</p>
<div class="variablelist"><dl>
<dt><span class="term"><strong class="userinput"><code>reload</code></strong></span></dt>
<dd><p>
Reload configuration file and zones.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>reload <em class="replaceable"><code>zone</code></em>
[<span class="optional"><em class="replaceable"><code>class</code></em>
[<span class="optional"><em class="replaceable"><code>view</code></em></span>]</span>]</code></strong></span></dt>
<dd><p>
Reload the given zone.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>refresh <em class="replaceable"><code>zone</code></em>
[<span class="optional"><em class="replaceable"><code>class</code></em>
[<span class="optional"><em class="replaceable"><code>view</code></em></span>]</span>]</code></strong></span></dt>
<dd><p>
Schedule zone maintenance for the given zone.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>retransfer <em class="replaceable"><code>zone</code></em>
[<span class="optional"><em class="replaceable"><code>class</code></em>
[<span class="optional"><em class="replaceable"><code>view</code></em></span>]</span>]</code></strong></span></dt>
<dd><p>
Retransfer the given zone from the master.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>freeze
[<span class="optional"><em class="replaceable"><code>zone</code></em>
[<span class="optional"><em class="replaceable"><code>class</code></em>
[<span class="optional"><em class="replaceable"><code>view</code></em></span>]</span>]</span>]</code></strong></span></dt>
<dd><p>
Suspend updates to a dynamic zone. If no zone is
specified
then all zones are suspended. This allows manual
edits to be made to a zone normally updated by dynamic
update. It
also causes changes in the journal file to be synced
into the master
and the journal file to be removed. All dynamic
update attempts will
be refused while the zone is frozen.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>thaw
[<span class="optional"><em class="replaceable"><code>zone</code></em>
[<span class="optional"><em class="replaceable"><code>class</code></em>
[<span class="optional"><em class="replaceable"><code>view</code></em></span>]</span>]</span>]</code></strong></span></dt>
<dd><p>
Enable updates to a frozen dynamic zone. If no zone
is
specified then all frozen zones are enabled. This
causes
the server to reload the zone from disk, and
re-enables dynamic updates
after the load has completed. After a zone is thawed,
dynamic updates
will no longer be refused.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>notify <em class="replaceable"><code>zone</code></em>
[<span class="optional"><em class="replaceable"><code>class</code></em>
[<span class="optional"><em class="replaceable"><code>view</code></em></span>]</span>]</code></strong></span></dt>
<dd><p>
Resend NOTIFY messages for the zone.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>reconfig</code></strong></span></dt>
<dd><p>
Reload the configuration file and load new zones,
but do not reload existing zone files even if they
have changed.
This is faster than a full <span><strong class="command">reload</strong></span> when there
is a large number of zones because it avoids the need
to examine the
modification times of the zones files.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>stats</code></strong></span></dt>
<dd><p>
Write server statistics to the statistics file.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>querylog</code></strong></span></dt>
<dd><p>
Toggle query logging. Query logging can also be enabled
by explicitly directing the <span><strong class="command">queries</strong></span>
<span><strong class="command">category</strong></span> to a
<span><strong class="command">channel</strong></span> in the
<span><strong class="command">logging</strong></span> section of
<span><strong class="command">querylog yes;</strong></span> in the
<span><strong class="command">options</strong></span> section of
</p></dd>
<dt><span class="term"><strong class="userinput"><code>dumpdb
[<span class="optional">-all|-cache|-zone</span>]
[<span class="optional"><em class="replaceable"><code>view ...</code></em></span>]</code></strong></span></dt>
<dd><p>
Dump the server's caches (default) and / or zones to
the
dump file for the specified views. If no view is
specified all
views are dumped.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>stop [<span class="optional">-p</span>]</code></strong></span></dt>
<dd><p>
Stop the server, making sure any recent changes
made through dynamic update or IXFR are first saved to
the master files of the updated zones.
If -p is specified named's process id is returned.
This allows an external process to determine when named
had completed stopping.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>halt [<span class="optional">-p</span>]</code></strong></span></dt>
<dd><p>
Stop the server immediately. Recent changes
made through dynamic update or IXFR are not saved to
the master files, but will be rolled forward from the
journal files when the server is restarted.
If -p is specified named's process id is returned.
This allows an external process to determine when named
had completed halting.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>trace</code></strong></span></dt>
<dd><p>
Increment the servers debugging level by one.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>trace <em class="replaceable"><code>level</code></em></code></strong></span></dt>
<dd><p>
Sets the server's debugging level to an explicit
value.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>notrace</code></strong></span></dt>
<dd><p>
Sets the server's debugging level to 0.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>flush</code></strong></span></dt>
<dd><p>
Flushes the server's cache.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>flushname</code></strong> <em class="replaceable"><code>name</code></em></span></dt>
<dd><p>
Flushes the given name from the server's cache.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>status</code></strong></span></dt>
<dd><p>
Display status of the server.
Note the number of zones includes the internal <span><strong class="command">bind/CH</strong></span> zone
hint zone if there is not a
explicit root zone configured.
</p></dd>
<dt><span class="term"><strong class="userinput"><code>recursing</code></strong></span></dt>
<dd><p>
Dump the list of queries named is currently recursing
on.
</p></dd>
</dl></div>
<p>
In <span class="acronym">BIND</span> 9.2, <span><strong class="command">rndc</strong></span>
supports all the commands of the BIND 8 <span><strong class="command">ndc</strong></span>
utility except <span><strong class="command">ndc start</strong></span> and
<span><strong class="command">ndc restart</strong></span>, which were also
not supported in <span><strong class="command">ndc</strong></span>'s
channel mode.
</p>
<p>
A configuration file is required, since all
communication with the server is authenticated with
digital signatures that rely on a shared secret, and
there is no way to provide that secret other than with a
configuration file. The default location for the
<span><strong class="command">rndc</strong></span> configuration file is
alternate
location can be specified with the <code class="option">-c</code>
option. If the configuration file is not found,
<span><strong class="command">rndc</strong></span> will also look in
<code class="varname">sysconfdir</code> was defined when
the <span class="acronym">BIND</span> build was
configured).
generated by
running <span><strong class="command">rndc-confgen -a</strong></span> as
described in
<a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
Usage">the section called “<span><strong class="command">controls</strong></span> Statement Definition and
Usage”</a>.
</p>
<p>
The format of the configuration file is similar to
limited to
only four statements, the <span><strong class="command">options</strong></span>,
<span><strong class="command">key</strong></span>, <span><strong class="command">server</strong></span> and
<span><strong class="command">include</strong></span>
statements. These statements are what associate the
secret keys to the servers with which they are meant to
be shared. The order of statements is not
significant.
</p>
<p>
The <span><strong class="command">options</strong></span> statement has
three clauses:
<span><strong class="command">default-server</strong></span>, <span><strong class="command">default-key</strong></span>,
and <span><strong class="command">default-port</strong></span>.
<span><strong class="command">default-server</strong></span> takes a
host name or address argument and represents the server
that will
be contacted if no <code class="option">-s</code>
option is provided on the command line.
<span><strong class="command">default-key</strong></span> takes
the name of a key as its argument, as defined by a <span><strong class="command">key</strong></span> statement.
<span><strong class="command">default-port</strong></span> specifies the
port to which
<span><strong class="command">rndc</strong></span> should connect if no
port is given on the command line or in a
<span><strong class="command">server</strong></span> statement.
</p>
<p>
The <span><strong class="command">key</strong></span> statement defines an
key to be used
by <span><strong class="command">rndc</strong></span> when authenticating
with
<span><strong class="command">named</strong></span>. Its syntax is
identical to the
The keyword <strong class="userinput"><code>key</code></strong> is
followed by a key name, which must be a valid
domain name, though it need not actually be hierarchical;
thus,
a string like "<strong class="userinput"><code>rndc_key</code></strong>" is a valid
name.
The <span><strong class="command">key</strong></span> statement has two
clauses:
<span><strong class="command">algorithm</strong></span> and <span><strong class="command">secret</strong></span>.
While the configuration parser will accept any string as the
argument
to algorithm, currently only the string "<strong class="userinput"><code>hmac-md5</code></strong>"
has any meaning. The secret is a base-64 encoded string
as specified in RFC 3548.
</p>
<p>
The <span><strong class="command">server</strong></span> statement
associates a key
defined using the <span><strong class="command">key</strong></span>
statement with a server.
The keyword <strong class="userinput"><code>server</code></strong> is followed by a
host name or address. The <span><strong class="command">server</strong></span> statement
has two clauses: <span><strong class="command">key</strong></span> and <span><strong class="command">port</strong></span>.
The <span><strong class="command">key</strong></span> clause specifies the
name of the key
to be used when communicating with this server, and the
<span><strong class="command">port</strong></span> clause can be used to
specify the port <span><strong class="command">rndc</strong></span> should
connect
to on the server.
</p>
<p>
A sample minimal configuration file is as follows:
</p>
<pre class="programlisting">
key rndc_key {
algorithm "hmac-md5";
secret "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K";
};
options {
default-server 127.0.0.1;
default-key rndc_key;
};
</pre>
<p>
would allow the command:
</p>
<p>
<code class="prompt">$ </code><strong class="userinput"><code>rndc reload</code></strong>
</p>
<p>
to connect to 127.0.0.1 port 953 and cause the name server
to reload, if a name server on the local machine were
running with
following controls statements:
</p>
<pre class="programlisting">
controls {
inet 127.0.0.1 allow { localhost; } keys { rndc_key; };
};
</pre>
<p>
and it had an identical key statement for
<code class="literal">rndc_key</code>.
</p>
<p>
Running the <span><strong class="command">rndc-confgen</strong></span>
program will
file for you, and also display the
corresponding <span><strong class="command">controls</strong></span>
statement that you need to
Alternatively,
you can run <span><strong class="command">rndc-confgen -a</strong></span>
to set up
modify
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2550907"></a>Signals</h3></div></div></div>
<p>
Certain UNIX signals cause the name server to take specific
actions, as described in the following table. These signals can
be sent using the <span><strong class="command">kill</strong></span> command.
</p>
<div class="informaltable"><table border="1">
<colgroup>
<col>
<col>
</colgroup>
<tbody>
<tr>
<td>
<p><span><strong class="command">SIGHUP</strong></span></p>
</td>
<td>
<p>
reload the database.
</p>
</td>
</tr>
<tr>
<td>
<p><span><strong class="command">SIGTERM</strong></span></p>
</td>
<td>
<p>
Causes the server to clean up and exit.
</p>
</td>
</tr>
<tr>
<td>
<p><span><strong class="command">SIGINT</strong></span></p>
</td>
<td>
<p>
Causes the server to clean up and exit.
</p>
</td>
</tr>
</tbody>
</table></div>
</div>
</div>
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