Documentation rebuild

containers apply enclosed configuration directives only

to sites accessed through <code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code>'s proxy server

that match the specified URL. For example, the following configuration

will prevent the proxy server from being used to access the

<code>www.example.com</code> website.</p>

will allow only a subset of clients to access the

<code>www.example.com</code> website using the proxy server:</p>

<pre class="prettyprint lang-config">&lt;Proxy "http://www.example.com/*"&gt;

    Require all granted

    Require host yournetwork.example.com

&lt;/Proxy&gt;</pre>

</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>

    container takes the place of the <code class="directive"><a href="./mod/core.html#directory">&lt;Directory&gt;</a></code> container in the processing

    order.</p>

    <p>Later sections override earlier ones, however each module is responsible

    for interpreting what form this override takes.  A later configuration section 

    with directives from a given module might cause a conceptual "merge" of some

    directives, all directives, or a complete replacement of the modules 

    configuration with the module defaults and directives explicitly listed in 

    the later context.</p>

    <div class="note"><h3>Technical Note</h3>

      There is actually a

      <code>&lt;Location&gt;</code>/<code>&lt;LocationMatch&gt;</code>

      completed.

    </div>

<h3><a name="merge-examples" id="merge-examples">Some Examples</a></h3>

<h3><a name="relationship-module-configuration" id="relationship-module-configuration">Relationship between modules and configuration sections</a></h3>

    <p>One question that often arises after reading how configuration sections are

    merged is related to how and when directives of specific modules like <code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code>

    are processed. The answer is not trivial and needs a bit of background. 

    Each httpd module manages its own configuration, and each of its directives in httpd.conf specify one piece 

    of configuration in a particular context. httpd does not execute a command as it is read.</p>

    <p>At runtime, the core of httpd iterates over the defined configuration sections in the order

    described above to determine which ones apply to the current request. When the first section matches, 

    it is considered the current configuration for this request. If a subsequent section matches too, 

    then each module with a directive in either of the sections is given a chance to merge its configuration between the two sections. The result is a third configuration, and the process goes on until all the configuration sections

    are evaluated.</p>

    <p>After the above step, the "real" processing of the HTTP request begins: each module has a chance to run 

    and perform whatever tasks they like. They can retrieve their own final merged configuration from the core

    of the httpd to determine how they should act.</p>

    <p>An example can help to visualize the whole process. The following configuration uses the 

        <code class="directive"><a href="./mod/mod_headers.html#header">Header</a></code> directive of <code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code> to set

        a specific HTTP header. What value will httpd set in the <code>CustomHeaderName</code> header for a request to

        <code>/example/index.html</code> ?

    </p>

    <pre class="prettyprint lang-config">&lt;Directory "/"&gt;

    Header set CustomHeaderName one

    <FilesMatch ".*">

        Header set CustomHeaderName three

    </FilesMatch>

</Directory>

<Directory "/example">

    Header set CustomHeaderName two

&lt;/Directory&gt;</pre>

    <ul>

        <li><code class="directive">Directory</code> "/" matches and an initial configuration to set the <code>CustomHeaderName</code> header with the value <code>one</code> is created.</li>

        <li><code class="directive">Directory</code> "/example" matches, and since <code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code> specifies in its code to override in case of a merge, a new configuration is created to set the <code>CustomHeaderName</code> header with the value <code>two</code>.</li>

        <li><code class="directive">FilesMatch</code> ".*" matches and another merge opportunity arises, causing the <code>CustomHeaderName</code> header to be set with the value <code>three</code>.</li>

        <li>Eventually during the next steps of the HTTP request processing <code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code> will be called and it will receive the configuration to set the <code>CustomHeaderName</code> header with the value <code>three</code>. <code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code> normally uses this configuration to perfom its job, namely setting the foo header. This does not mean that a module can't perform a more complex action like discarding directives because not needed or deprecated, etc..</li>

    </ul>

    <p>This is true for .htaccess too since they have the same priority as <code class="directive">Directory</code> in the merge order. The important concept to understand is that configuration sections like  <code class="directive">Directory</code> and <code class="directive">FilesMatch</code> are not comparable to module specific directives like <code class="directive"><a href="./mod/mod_headers.html#header">Header</a></code> or <code class="directive"><a href="./mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> because they operate on different levels.

    </p>

<h3><a name="merge-examples" id="merge-examples">Some useful examples</a></h3>

<p>Below is an artificial example to show the order of

merging. Assuming they all apply to the request, the directives in

&lt;/Directory&gt;</pre>

<p>For a more concrete example, consider the following.  Regardless of

any access restrictions placed in <code class="directive"><a href="./mod/core.html#directory">&lt;Directory&gt;</a></code> sections, the <code class="directive"><a href="./mod/core.html#location">&lt;Location&gt;</a></code> section will be

evaluated last and will allow unrestricted access to the server.  In