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42<div class="titlepage"><div><div><h1 class="title">
43<a name="Bv9ARM.ch03"></a>Chapter�3.�Name Server Configuration</h1></div></div></div>
44<div class="toc">
45<p><b>Table of Contents</b></p>
46<dl class="toc">
47<dt><span class="section"><a href="Bv9ARM.ch03.html#sample_configuration">Sample Configurations</a></span></dt>
48<dd><dl>
49<dt><span class="section"><a href="Bv9ARM.ch03.html#cache_only_sample">A Caching-only Name Server</a></span></dt>
50<dt><span class="section"><a href="Bv9ARM.ch03.html#auth_only_sample">An Authoritative-only Name Server</a></span></dt>
51</dl></dd>
52<dt><span class="section"><a href="Bv9ARM.ch03.html#load_balancing">Load Balancing</a></span></dt>
53<dt><span class="section"><a href="Bv9ARM.ch03.html#ns_operations">Name Server Operations</a></span></dt>
54<dd><dl>
55<dt><span class="section"><a href="Bv9ARM.ch03.html#tools">Tools for Use With the Name Server Daemon</a></span></dt>
56<dt><span class="section"><a href="Bv9ARM.ch03.html#signals">Signals</a></span></dt>
57</dl></dd>
58</dl>
59</div>
60<p>
61      In this chapter we provide some suggested configurations along
62      with guidelines for their use.  We suggest reasonable values for
63      certain option settings.
64    </p>
65<div class="section">
66<div class="titlepage"><div><div><h2 class="title" style="clear: both">
67<a name="sample_configuration"></a>Sample Configurations</h2></div></div></div>
68<div class="section">
69<div class="titlepage"><div><div><h3 class="title">
70<a name="cache_only_sample"></a>A Caching-only Name Server</h3></div></div></div>
71<p>
72          The following sample configuration is appropriate for a caching-only
73          name server for use by clients internal to a corporation.  All
74          queries
75          from outside clients are refused using the <span class="command"><strong>allow-query</strong></span>
76          option.  Alternatively, the same effect could be achieved using
77          suitable
78          firewall rules.
79        </p>
80<pre class="programlisting">
81// Two corporate subnets we wish to allow queries from.
82acl corpnets { 192.168.4.0/24; 192.168.7.0/24; };
83options {
84     // Working directory
85     directory "/etc/namedb";
86
87     allow-query { corpnets; };
88};
89// Provide a reverse mapping for the loopback
90// address 127.0.0.1
91zone "0.0.127.in-addr.arpa" {
92     type master;
93     file "localhost.rev";
94     notify no;
95};
96</pre>
97</div>
98<div class="section">
99<div class="titlepage"><div><div><h3 class="title">
100<a name="auth_only_sample"></a>An Authoritative-only Name Server</h3></div></div></div>
101<p>
102          This sample configuration is for an authoritative-only server
103          that is the master server for "<code class="filename">example.com</code>"
104          and a slave for the subdomain "<code class="filename">eng.example.com</code>".
105        </p>
106<pre class="programlisting">
107options {
108     // Working directory
109     directory "/etc/namedb";
110     // Do not allow access to cache
111     allow-query-cache { none; };
112     // This is the default
113     allow-query { any; };
114     // Do not provide recursive service
115     recursion no;
116};
117
118// Provide a reverse mapping for the loopback
119// address 127.0.0.1
120zone "0.0.127.in-addr.arpa" {
121     type master;
122     file "localhost.rev";
123     notify no;
124};
125// We are the master server for example.com
126zone "example.com" {
127     type master;
128     file "example.com.db";
129     // IP addresses of slave servers allowed to
130     // transfer example.com
131     allow-transfer {
132          192.168.4.14;
133          192.168.5.53;
134     };
135};
136// We are a slave server for eng.example.com
137zone "eng.example.com" {
138     type slave;
139     file "eng.example.com.bk";
140     // IP address of eng.example.com master server
141     masters { 192.168.4.12; };
142};
143</pre>
144</div>
145</div>
146<div class="section">
147<div class="titlepage"><div><div><h2 class="title" style="clear: both">
148<a name="load_balancing"></a>Load Balancing</h2></div></div></div>
149<p>
150        A primitive form of load balancing can be achieved in
151        the <acronym class="acronym">DNS</acronym> by using multiple records
152        (such as multiple A records) for one name.
153      </p>
154<p>
155        For example, if you have three WWW servers with network addresses
156        of 10.0.0.1, 10.0.0.2 and 10.0.0.3, a set of records such as the
157        following means that clients will connect to each machine one third
158        of the time:
159      </p>
160<div class="informaltable"><table border="1">
161<colgroup>
162<col width="0.875in" class="1">
163<col width="0.500in" class="2">
164<col width="0.750in" class="3">
165<col width="0.750in" class="4">
166<col width="2.028in" class="5">
167</colgroup>
168<tbody>
169<tr>
170<td>
171                <p>
172                  Name
173                </p>
174              </td>
175<td>
176                <p>
177                  TTL
178                </p>
179              </td>
180<td>
181                <p>
182                  CLASS
183                </p>
184              </td>
185<td>
186                <p>
187                  TYPE
188                </p>
189              </td>
190<td>
191                <p>
192                  Resource Record (RR) Data
193                </p>
194              </td>
195</tr>
196<tr>
197<td>
198                <p>
199                  <code class="literal">www</code>
200                </p>
201              </td>
202<td>
203                <p>
204                  <code class="literal">600</code>
205                </p>
206              </td>
207<td>
208                <p>
209                  <code class="literal">IN</code>
210                </p>
211              </td>
212<td>
213                <p>
214                  <code class="literal">A</code>
215                </p>
216              </td>
217<td>
218                <p>
219                  <code class="literal">10.0.0.1</code>
220                </p>
221              </td>
222</tr>
223<tr>
224<td>
225                <p></p>
226              </td>
227<td>
228                <p>
229                  <code class="literal">600</code>
230                </p>
231              </td>
232<td>
233                <p>
234                  <code class="literal">IN</code>
235                </p>
236              </td>
237<td>
238                <p>
239                  <code class="literal">A</code>
240                </p>
241              </td>
242<td>
243                <p>
244                  <code class="literal">10.0.0.2</code>
245                </p>
246              </td>
247</tr>
248<tr>
249<td>
250                <p></p>
251              </td>
252<td>
253                <p>
254                  <code class="literal">600</code>
255                </p>
256              </td>
257<td>
258                <p>
259                  <code class="literal">IN</code>
260                </p>
261              </td>
262<td>
263                <p>
264                  <code class="literal">A</code>
265                </p>
266              </td>
267<td>
268                <p>
269                  <code class="literal">10.0.0.3</code>
270                </p>
271              </td>
272</tr>
273</tbody>
274</table></div>
275<p>
276        When a resolver queries for these records, <acronym class="acronym">BIND</acronym> will rotate
277        them and respond to the query with the records in a different
278        order.  In the example above, clients will randomly receive
279        records in the order 1, 2, 3; 2, 3, 1; and 3, 1, 2. Most clients
280        will use the first record returned and discard the rest.
281      </p>
282<p>
283        For more detail on ordering responses, check the
284        <span class="command"><strong>rrset-order</strong></span> sub-statement in the
285        <span class="command"><strong>options</strong></span> statement, see
286        <a class="xref" href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">RRset Ordering</a>.
287      </p>
288</div>
289<div class="section">
290<div class="titlepage"><div><div><h2 class="title" style="clear: both">
291<a name="ns_operations"></a>Name Server Operations</h2></div></div></div>
292<div class="section">
293<div class="titlepage"><div><div><h3 class="title">
294<a name="tools"></a>Tools for Use With the Name Server Daemon</h3></div></div></div>
295<p>
296          This section describes several indispensable diagnostic,
297          administrative and monitoring tools available to the system
298          administrator for controlling and debugging the name server
299          daemon.
300        </p>
301<div class="section">
302<div class="titlepage"><div><div><h4 class="title">
303<a name="diagnostic_tools"></a>Diagnostic Tools</h4></div></div></div>
304<p>
305            The <span class="command"><strong>dig</strong></span>, <span class="command"><strong>host</strong></span>, and
306            <span class="command"><strong>nslookup</strong></span> programs are all command
307            line tools
308            for manually querying name servers.  They differ in style and
309            output format.
310          </p>
311<div class="variablelist"><dl class="variablelist">
312<dt><span class="term"><a name="dig"></a><span class="command"><strong>dig</strong></span></span></dt>
313<dd>
314<p>
315                  The domain information groper (<span class="command"><strong>dig</strong></span>)
316                  is the most versatile and complete of these lookup tools.
317                  It has two modes: simple interactive
318                  mode for a single query, and batch mode which executes a
319                  query for
320                  each in a list of several query lines. All query options are
321                  accessible
322                  from the command line.
323                </p>
324<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>
325<p>
326                  The usual simple use of <span class="command"><strong>dig</strong></span> will take the form
327                </p>
328<p class="simpara">
329                  <span class="command"><strong>dig @server domain query-type query-class</strong></span>
330                </p>
331<p>
332                  For more information and a list of available commands and
333                  options, see the <span class="command"><strong>dig</strong></span> man
334                  page.
335                </p>
336</dd>
337<dt><span class="term"><span class="command"><strong>host</strong></span></span></dt>
338<dd>
339<p>
340                  The <span class="command"><strong>host</strong></span> utility emphasizes
341                  simplicity
342                  and ease of use.  By default, it converts
343                  between host names and Internet addresses, but its
344                  functionality
345                  can be extended with the use of options.
346                </p>
347<div class="cmdsynopsis"><p><code class="command">host</code>  [-aCdlnrsTwv] [-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>] [-m <em class="replaceable"><code>flag</code></em>] [-4] [-6]  <em class="replaceable"><code>hostname</code></em>  [<em class="replaceable"><code>server</code></em>]</p></div>
348<p>
349                  For more information and a list of available commands and
350                  options, see the <span class="command"><strong>host</strong></span> man
351                  page.
352                </p>
353</dd>
354<dt><span class="term"><span class="command"><strong>nslookup</strong></span></span></dt>
355<dd>
356<p><span class="command"><strong>nslookup</strong></span>
357                  has two modes: interactive and
358                  non-interactive. Interactive mode allows the user to
359                  query name servers for information about various
360                  hosts and domains or to print a list of hosts in a
361                  domain. Non-interactive mode is used to print just
362                  the name and requested information for a host or
363                  domain.
364                </p>
365<div class="cmdsynopsis"><p><code class="command">nslookup</code>  [-option...] [[<em class="replaceable"><code>host-to-find</code></em>] |  [- [server]]]</p></div>
366<p>
367                  Interactive mode is entered when no arguments are given (the
368                  default name server will be used) or when the first argument
369                  is a
370                  hyphen (`-') and the second argument is the host name or
371                  Internet address
372                  of a name server.
373                </p>
374<p>
375                  Non-interactive mode is used when the name or Internet
376                  address
377                  of the host to be looked up is given as the first argument.
378                  The
379                  optional second argument specifies the host name or address
380                  of a name server.
381                </p>
382<p>
383                  Due to its arcane user interface and frequently inconsistent
384                  behavior, we do not recommend the use of <span class="command"><strong>nslookup</strong></span>.
385                  Use <span class="command"><strong>dig</strong></span> instead.
386                </p>
387</dd>
388</dl></div>
389</div>
390<div class="section">
391<div class="titlepage"><div><div><h4 class="title">
392<a name="admin_tools"></a>Administrative Tools</h4></div></div></div>
393<p>
394            Administrative tools play an integral part in the management
395            of a server.
396          </p>
397<div class="variablelist"><dl class="variablelist">
398<dt>
399<a name="named-checkconf"></a><span class="term"><span class="command"><strong>named-checkconf</strong></span></span>
400</dt>
401<dd>
402<p>
403                  The <span class="command"><strong>named-checkconf</strong></span> program
404                  checks the syntax of a <code class="filename">named.conf</code> file.
405                </p>
406<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>
407</dd>
408<dt>
409<a name="named-checkzone"></a><span class="term"><span class="command"><strong>named-checkzone</strong></span></span>
410</dt>
411<dd>
412<p>
413                  The <span class="command"><strong>named-checkzone</strong></span> program
414                  checks a master file for
415                  syntax and consistency.
416                </p>
417<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>
418</dd>
419<dt>
420<a name="named-compilezone"></a><span class="term"><span class="command"><strong>named-compilezone</strong></span></span>
421</dt>
422<dd><p>
423                  Similar to <span class="command"><strong>named-checkzone,</strong></span> but
424                  it always dumps the zone content to a specified file
425                  (typically in a different format).
426                </p></dd>
427<dt>
428<a name="rndc"></a><span class="term"><span class="command"><strong>rndc</strong></span></span>
429</dt>
430<dd>
431<p>
432                  The remote name daemon control
433                  (<span class="command"><strong>rndc</strong></span>) program allows the
434                  system
435                  administrator to control the operation of a name server.
436                  Since <acronym class="acronym">BIND</acronym> 9.2, <span class="command"><strong>rndc</strong></span>
437                  supports all the commands of the BIND 8 <span class="command"><strong>ndc</strong></span>
438                  utility except <span class="command"><strong>ndc start</strong></span> and
439                  <span class="command"><strong>ndc restart</strong></span>, which were also
440                  not supported in <span class="command"><strong>ndc</strong></span>'s
441                  channel mode.
442                  If you run <span class="command"><strong>rndc</strong></span> without any
443                  options
444                  it will display a usage message as follows:
445                </p>
446<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>
447<p>See <a class="xref" href="man.rndc.html" title="rndc"><span class="refentrytitle"><span class="application">rndc</span></span>(8)</a> for details of
448                  the available <span class="command"><strong>rndc</strong></span> commands.
449                </p>
450<p>
451                  <span class="command"><strong>rndc</strong></span> requires a configuration file,
452                  since all
453                  communication with the server is authenticated with
454                  digital signatures that rely on a shared secret, and
455                  there is no way to provide that secret other than with a
456                  configuration file.  The default location for the
457                  <span class="command"><strong>rndc</strong></span> configuration file is
458                  <code class="filename">/etc/rndc.conf</code>, but an
459                  alternate
460                  location can be specified with the <code class="option">-c</code>
461                  option.  If the configuration file is not found,
462                  <span class="command"><strong>rndc</strong></span> will also look in
463                  <code class="filename">/etc/rndc.key</code> (or whatever
464                  <code class="varname">sysconfdir</code> was defined when
465                  the <acronym class="acronym">BIND</acronym> build was
466                  configured).
467                  The <code class="filename">rndc.key</code> file is
468                  generated by
469                  running <span class="command"><strong>rndc-confgen -a</strong></span> as
470                  described in
471                  <a class="xref" href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and Usage">the section called &#8220;<span class="command"><strong>controls</strong></span> Statement Definition and
472          Usage&#8221;</a>.
473                </p>
474<p>
475                  The format of the configuration file is similar to
476                  that of <code class="filename">named.conf</code>, but
477                  limited to
478                  only four statements, the <span class="command"><strong>options</strong></span>,
479                  <span class="command"><strong>key</strong></span>, <span class="command"><strong>server</strong></span> and
480                  <span class="command"><strong>include</strong></span>
481                  statements.  These statements are what associate the
482                  secret keys to the servers with which they are meant to
483                  be shared.  The order of statements is not
484                  significant.
485                </p>
486<p>
487                  The <span class="command"><strong>options</strong></span> statement has
488                  three clauses:
489                  <span class="command"><strong>default-server</strong></span>, <span class="command"><strong>default-key</strong></span>,
490                  and <span class="command"><strong>default-port</strong></span>.
491                  <span class="command"><strong>default-server</strong></span> takes a
492                  host name or address argument  and represents the server
493                  that will
494                  be contacted if no <code class="option">-s</code>
495                  option is provided on the command line.
496                  <span class="command"><strong>default-key</strong></span> takes
497                  the name of a key as its argument, as defined by a <span class="command"><strong>key</strong></span> statement.
498                  <span class="command"><strong>default-port</strong></span> specifies the
499                  port to which
500                  <span class="command"><strong>rndc</strong></span> should connect if no
501                  port is given on the command line or in a
502                  <span class="command"><strong>server</strong></span> statement.
503                </p>
504<p>
505                  The <span class="command"><strong>key</strong></span> statement defines a
506                  key to be used
507                  by <span class="command"><strong>rndc</strong></span> when authenticating
508                  with
509                  <span class="command"><strong>named</strong></span>.  Its syntax is
510                  identical to the
511                  <span class="command"><strong>key</strong></span> statement in <code class="filename">named.conf</code>.
512                  The keyword <strong class="userinput"><code>key</code></strong> is
513                  followed by a key name, which must be a valid
514                  domain name, though it need not actually be hierarchical;
515                  thus,
516                  a string like "<strong class="userinput"><code>rndc_key</code></strong>" is a valid
517                  name.
518                  The <span class="command"><strong>key</strong></span> statement has two
519                  clauses:
520                  <span class="command"><strong>algorithm</strong></span> and <span class="command"><strong>secret</strong></span>.
521                  While the configuration parser will accept any string as the
522                  argument
523                  to algorithm, currently only the string "<strong class="userinput"><code>hmac-md5</code></strong>"
524                  has any meaning.  The secret is a base-64 encoded string
525                  as specified in RFC 3548.
526                </p>
527<p>
528                  The <span class="command"><strong>server</strong></span> statement
529                  associates a key
530                  defined using the <span class="command"><strong>key</strong></span>
531                  statement with a server.
532                  The keyword <strong class="userinput"><code>server</code></strong> is followed by a
533                  host name or address.  The <span class="command"><strong>server</strong></span> statement
534                  has two clauses: <span class="command"><strong>key</strong></span> and <span class="command"><strong>port</strong></span>.
535                  The <span class="command"><strong>key</strong></span> clause specifies the
536                  name of the key
537                  to be used when communicating with this server, and the
538                  <span class="command"><strong>port</strong></span> clause can be used to
539                  specify the port <span class="command"><strong>rndc</strong></span> should
540                  connect
541                  to on the server.
542                </p>
543<p>
544                  A sample minimal configuration file is as follows:
545                </p>
546<pre class="programlisting">
547key rndc_key {
548     algorithm "hmac-md5";
549     secret
550       "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K";
551};
552options {
553     default-server 127.0.0.1;
554     default-key    rndc_key;
555};
556</pre>
557<p>
558                  This file, if installed as <code class="filename">/etc/rndc.conf</code>,
559                  would allow the command:
560                </p>
561<p>
562                  <code class="prompt">$ </code><strong class="userinput"><code>rndc reload</code></strong>
563                </p>
564<p>
565                  to connect to 127.0.0.1 port 953 and cause the name server
566                  to reload, if a name server on the local machine were
567                  running with
568                  following controls statements:
569                </p>
570<pre class="programlisting">
571controls {
572        inet 127.0.0.1
573            allow { localhost; } keys { rndc_key; };
574};
575</pre>
576<p>
577                  and it had an identical key statement for
578                  <code class="literal">rndc_key</code>.
579                </p>
580<p>
581                  Running the <span class="command"><strong>rndc-confgen</strong></span>
582                  program will
583                  conveniently create a <code class="filename">rndc.conf</code>
584                  file for you, and also display the
585                  corresponding <span class="command"><strong>controls</strong></span>
586                  statement that you need to
587                  add to <code class="filename">named.conf</code>.
588                  Alternatively,
589                  you can run <span class="command"><strong>rndc-confgen -a</strong></span>
590                  to set up
591                  a <code class="filename">rndc.key</code> file and not
592                  modify
593                  <code class="filename">named.conf</code> at all.
594                </p>
595</dd>
596</dl></div>
597</div>
598</div>
599<div class="section">
600<div class="titlepage"><div><div><h3 class="title">
601<a name="signals"></a>Signals</h3></div></div></div>
602<p>
603          Certain UNIX signals cause the name server to take specific
604          actions, as described in the following table.  These signals can
605          be sent using the <span class="command"><strong>kill</strong></span> command.
606        </p>
607<div class="informaltable"><table border="1">
608<colgroup>
609<col width="1.125in" class="1">
610<col width="4.000in" class="2">
611</colgroup>
612<tbody>
613<tr>
614<td>
615                  <p><span class="command"><strong>SIGHUP</strong></span></p>
616                </td>
617<td>
618                  <p>
619                    Causes the server to read <code class="filename">named.conf</code> and
620                    reload the database.
621                  </p>
622                </td>
623</tr>
624<tr>
625<td>
626                  <p><span class="command"><strong>SIGTERM</strong></span></p>
627                </td>
628<td>
629                  <p>
630                    Causes the server to clean up and exit.
631                  </p>
632                </td>
633</tr>
634<tr>
635<td>
636                  <p><span class="command"><strong>SIGINT</strong></span></p>
637                </td>
638<td>
639                  <p>
640                    Causes the server to clean up and exit.
641                  </p>
642                </td>
643</tr>
644</tbody>
645</table></div>
646</div>
647</div>
648</div>
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