title: mod_headers module does not load, though it's enabled in httpd.conf
body: <p>I need <code>mod_headers</code> to force download of a file depending on GET parameter.</p>
  
  <pre><code>  &lt;FilesMatch "*.gif"&gt;
       &lt;If "%{QUERY_STRING} =~ /dl/"&gt;
          #Download header
          Header set Content-Disposition "attachment"
       &lt;/If&gt;
    &lt;/FilesMatch&gt;
  </code></pre>
  
  <p>Code above produces an error 500. However, if I wrap it properly in <code>&lt;IfModule&gt;</code>, it does not do anything at all:</p>
  
  <pre><code>&lt;IfModule mod_headers&gt;
    &lt;FilesMatch "*.gif"&gt;
       &lt;If "%{QUERY_STRING} =~ /dl/"&gt;
          Header set Content-Disposition "attachment"
       &lt;/If&gt;
    &lt;/FilesMatch&gt;
  &lt;/IfModule&gt;
  </code></pre>
  
  <p>This makes me think that <code>mod_headers</code> didn't load at all. But I have it enabled in <code>httpd.conf</code>:</p>
  
  <blockquote>
    <p>...<br>
    LoadModule filter_module modules/mod_filter.so<br>
    LoadModule headers_module modules/<strong>mod_headers.so</strong><br>
    <code>#</code>LoadModule heartbeat_module modules/mod_heartbeat.so<br>
    ...  </p>
  </blockquote>
  
  <p>Is there any debug log to find out what mods have been loaded and what not?</p>