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+<manualpage metafile="sections.xml.meta">
<title>Configuration Sections</title>
<related>
<modulelist>
<module>core</module>
+<module>mod_version</module>
<module>mod_proxy</module>
</modulelist>
<directivelist>
<directive type="section" module="core">DirectoryMatch</directive>
<directive type="section" module="core">Files</directive>
<directive type="section" module="core">FilesMatch</directive>
+<directive type="section" module="core">If</directive>
<directive type="section" module="core">IfDefine</directive>
<directive type="section" module="core">IfModule</directive>
+<directive type="section" module="mod_version">IfVersion</directive>
<directive type="section" module="core">Location</directive>
<directive type="section" module="core">LocationMatch</directive>
<directive type="section" module="mod_proxy">Proxy</directive>
<p>There are two basic types of containers. Most containers are
evaluated for each request. The enclosed directives are applied only
for those requests that match the containers. The <directive
-type="section" module="core">IfDefine</directive> and <directive
-type="section" module="core">IfModule</directive> containers, on the
-other hand, are evaluated only at server startup and restart. If
-their conditions are true at startup, then the enclosed directives
-will apply to all requests. If the conditions are not true, the
-enclosed directives will be ignored.</p>
+type="section" module="core">IfDefine</directive>, <directive
+type="section" module="core">IfModule</directive>, and
+<directive type="section" module="mod_version">IfVersion</directive>
+containers, on the other hand, are evaluated only at server startup
+and restart. If their conditions are true at startup, then the
+enclosed directives will apply to all requests. If the conditions are
+not true, the enclosed directives will be ignored.</p>
<p>The <directive type="section" module="core">IfDefine</directive> directive
encloses directives that will only be applied if an appropriate
-parameter is defined on the <code>httpd</code> command line. For example,
+parameter is defined on the <program>httpd</program> command line. For example,
with the following configuration, all requests will be redirected
to another site only if the server is started using
<code>httpd -DClosedForNow</code>:</p>
-<example>
-<IfDefine ClosedForNow><br />
-Redirect / http://otherserver.example.com/<br />
+<highlight language="config">
+<IfDefine ClosedForNow>
+ Redirect "/" "http://otherserver.example.com/"
</IfDefine>
-</example>
+</highlight>
<p>The <directive type="section" module="core">IfModule</directive>
directive is very similar, except it encloses directives that will
about missing modules.</p>
<p>In the following example, the <directive
-module="mod_mime_magic">MimeMagicFiles</directive> directive will be
+module="mod_mime_magic">MimeMagicFile</directive> directive will be
applied only if <module>mod_mime_magic</module> is available.</p>
-<example>
-<IfModule mod_mime_magic.c><br />
-MimeMagicFile conf/magic<br />
+<highlight language="config">
+<IfModule mod_mime_magic.c>
+ MimeMagicFile conf/magic
</IfModule>
-</example>
-
-<p>Both <directive type="section" module="core">IfDefine</directive>
-and <directive type="section" module="core">IfModule</directive>
+</highlight>
+
+<p>The <directive type="section" module="mod_version">IfVersion</directive>
+directive is very similar to <directive type="section"
+module="core">IfDefine</directive> and <directive type="section"
+module="core">IfModule</directive>, except it encloses directives that will
+only be applied if a particular version of the server is executing. This
+module is designed for the use in test suites and large networks which have to
+deal with different httpd versions and different configurations.</p>
+
+<highlight language="config">
+<IfVersion >= 2.4>
+ # this happens only in versions greater or
+ # equal 2.4.0.
+</IfVersion>
+</highlight>
+
+<p><directive type="section" module="core">IfDefine</directive>,
+<directive type="section" module="core">IfModule</directive>, and the
+<directive type="section" module="mod_version">IfVersion</directive>
can apply negative conditions by preceding their test with "!".
Also, these sections can be nested to achieve more complex
restrictions.</p>
</section>
-<section id="file-and-web"><title>Filesystem and Webspace</title>
+<section id="file-and-web"><title>Filesystem, Webspace, and Boolean Expressions</title>
<p>The most commonly used configuration section containers are the
ones that change the configuration of particular places in the
filesystem or webspace. First, it is important to understand the
difference between the two. The filesystem is the view of your disks
as seen by your operating system. For example, in a default install,
-Apache resides at <code>/usr/local/apache2</code> in the Unix
+Apache httpd resides at <code>/usr/local/apache2</code> in the Unix
filesystem or <code>"c:/Program Files/Apache Group/Apache2"</code> in
the Windows filesystem. (Note that forward slashes should always be
-used as the path separator in Apache, even for Windows.) In contrast,
+used as the path separator in Apache httpd configuration files, even for Windows.) In contrast,
the webspace is the view of your site as delivered by the web server
and seen by the client. So the path <code>/dir/</code> in the
webspace corresponds to the path
<code>/usr/local/apache2/htdocs/dir/</code> in the filesystem of a
-default Apache install on Unix. The webspace need not map directly to
+default Apache httpd install on Unix. The webspace need not map directly to
the filesystem, since webpages may be generated dynamically
from databases or other locations.</p>
<p>The <directive type="section" module="core">Directory</directive>
and <directive type="section" module="core">Files</directive>
-directives, along with their regex counterparts, apply directives to
+directives, along with their <glossary ref="regex">regex</glossary>
+counterparts, apply directives to
parts of the filesystem. Directives enclosed in a <directive
type="section" module="core">Directory</directive> section apply to
the named filesystem directory and all subdirectories of that
-directory. The same effect can be obtained using <a
+directory (as well as the files in those directories).
+The same effect can be obtained using <a
href="howto/htaccess.html">.htaccess files</a>. For example, in the
following configuration, directory indexes will be enabled for the
<code>/var/web/dir1</code> directory and all subdirectories.</p>
-<example>
-<Directory /var/web/dir1><br />
-Options +Indexes<br />
+<highlight language="config">
+<Directory "/var/web/dir1">
+ Options +Indexes
</Directory>
-</example>
+</highlight>
<p>Directives enclosed in a <directive type="section"
module="core">Files</directive> section apply to any file with
deny access to any file named <code>private.html</code> regardless
of where it is found.</p>
-<example>
-<Files private.html><br />
-Order allow,deny<br />
-Deny from all<br />
+<highlight language="config">
+<Files "private.html">
+ Require all denied
</Files>
-</example>
+</highlight>
<p>To address files found in a particular part of the filesystem, the
<directive type="section" module="core">Files</directive> and
of <code>private.html</code> found under the <code>/var/web/dir1/</code>
directory.</p>
-<example>
-<Directory /var/web/dir1><br />
-<Files private.html><br />
-Order allow,deny<br />
-Deny from all<br />
-</Files><br />
+<highlight language="config">
+<Directory "/var/web/dir1">
+ <Files "private.html">
+ Require all denied
+ </Files>
</Directory>
-</example>
+</highlight>
</section>
<section id="webspace"><title>Webspace Containers</title>
<p>The <directive type="section" module="core">Location</directive>
-directive and its regex counterpart, on the other hand, change the
+directive and its <glossary ref="regex">regex</glossary> counterpart, on
+the other hand, change the
configuration for content in the webspace. For example, the following
configuration prevents access to any URL-path that begins in /private.
In particular, it will apply to requests for
<code>http://yoursite.example.com/private/dir/file.html</code> as well
as any other requests starting with the <code>/private</code> string.</p>
-<example>
-<Location /private><br />
-Order Allow,Deny<br />
-Deny from all<br />
-</Location>
-</example>
+<highlight language="config">
+<LocationMatch "^/private">
+ Require all denied
+</LocationMatch>
+</highlight>
<p>The <directive type="section" module="core">Location</directive>
directive need not have anything to do with the filesystem.
For example, the following example shows how to map a particular
-URL to an internal Apache handler provided by <module>mod_status</module>.
+URL to an internal Apache HTTP Server handler provided by <module>mod_status</module>.
No file called <code>server-status</code> needs to exist in the
filesystem.</p>
-<example>
-<Location /server-status><br />
-SetHandler server-status<br />
+<highlight language="config">
+<Location "/server-status">
+ SetHandler server-status
</Location>
-</example>
+</highlight>
+</section>
+
+<section id="overlapping-webspace"><title>Overlapping Webspace</title>
+<p>In order to have two overlapping URLs one has to consider the order in which
+certain sections or directives are evaluated. For
+<directive type="section" module="core">Location</directive> this would be:</p>
+<highlight language="config">
+<Location "/foo">
+</Location>
+<Location "/foo/bar">
+</Location>
+</highlight>
+<p><directive type="section" module="mod_alias">Alias</directive>es on the other hand,
+are mapped vice-versa:</p>
+<highlight language="config">
+Alias "/foo/bar" "/srv/www/uncommon/bar"
+Alias "/foo" "/srv/www/common/foo"
+</highlight>
+<p>The same is true for the <directive module="mod_proxy">ProxyPass</directive>
+directives:</p>
+<highlight language="config">
+ProxyPass "/special-area" "http://special.example.com" smax=5 max=10
+ProxyPass "/" "balancer://mycluster/" stickysession=JSESSIONID|jsessionid nofailover=On
+</highlight>
</section>
<section id="wildcards"><title>Wildcards and Regular Expressions</title>
explicitly.</p>
<p>If even more flexible matching is required, each
-container has a regular-expression (regex) counterpart <directive
+container has a regular expression (regex) counterpart <directive
type="section" module="core">DirectoryMatch</directive>, <directive
type="section" module="core">FilesMatch</directive>, and <directive
type="section" module="core">LocationMatch</directive> that allow
perl-compatible
-<a href="glossary.html#regex">regular expressions</a>
+<glossary ref="regex">regular expressions</glossary>
to be used in choosing the matches. But see the section below on
configuration merging to find out how using regex sections will change
how directives are applied.</p>
<p>A non-regex wildcard section that changes the configuration of
all user directories could look as follows:</p>
-<example>
-<Directory /home/*/public_html><br />
-Options Indexes<br />
+<highlight language="config">
+<Directory "/home/*/public_html">
+ Options Indexes
</Directory>
-</example>
+</highlight>
<p>Using regex sections, we can deny access to many types of image files
at once:</p>
-<example>
-<FilesMatch \.(?i:gif|jpe?g|png)$><br />
-Order allow,deny<br />
-Deny from all<br />
+<highlight language="config">
+<FilesMatch "\.(?i:gif|jpe?g|png)$">
+ Require all denied
</FilesMatch>
-</example>
+</highlight>
+
+<p>Regular expressions containing <strong>named groups and
+backreferences</strong> are added to the environment with the
+corresponding name in uppercase. This allows elements of filename paths
+and URLs to be referenced from within <a href="expr.html">expressions</a>
+and modules like <module>mod_rewrite</module>.</p>
+
+<highlight language="config">
+<DirectoryMatch "^/var/www/combined/(?<SITENAME>[^/]+)">
+ require ldap-group cn=%{env:MATCH_SITENAME},ou=combined,o=Example
+</DirectoryMatch>
+</highlight>
+
+</section>
+
+<section id="expressions"><title>Boolean expressions</title>
+<p>The <directive type="section" module="core">If</directive>
+directive change the configuration depending on a condition which can be
+expressed by a boolean expression. For example, the following configuration
+denies access if the HTTP Referer header does not start with
+"http://www.example.com/".</p>
+<highlight language="config">
+<If "!(%{HTTP_REFERER} -strmatch 'http://www.example.com/*')">
+ Require all denied
+</If>
+</highlight>
</section>
location, allowing your restrictions to be circumvented.
For example, consider the following configuration:</p>
-<example>
-<Location /dir/><br />
-Order allow,deny<br />
-Deny from all<br />
+<highlight language="config">
+<Location "/dir/">
+ Require all denied
</Location>
-</example>
+</highlight>
<p>This works fine if the request is for
<code>http://yoursite.example.com/dir/</code>. But what if you are on
filesystem location. Therefore you should always use the filesystem
containers when you can. There is, however, one exception to this
rule. Putting configuration restrictions in a <code><Location
-/></code> section is perfectly safe because this section will apply
+"/"></code> section is perfectly safe because this section will apply
to all requests regardless of the specific URL.</p>
</section>
+<section id="nesting"><title>Nesting of sections</title>
+
+<p>Some section types can be nested inside other section types. On the one
+hand, <directive type="section" module="core">Files</directive> can be used
+inside <directive type="section" module="core">Directory</directive>. On
+the other hand, <directive type="section" module="core">If</directive> can
+be used inside <directive type="section" module="core">Directory</directive>,
+<directive type="section" module="core">Location</directive>, and <directive
+type="section" module="core">Files</directive> sections. The regex
+counterparts of the named section behave identically.</p>
+
+<p>Nested sections are merged after non-nested sections of the same type.</p>
+
+</section>
+
</section>
<section id="virtualhost"><title>Virtual Hosts</title>
and <directive type="section" module="mod_proxy">ProxyMatch</directive>
containers apply enclosed configuration directives only
to sites accessed through <module>mod_proxy</module>'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>cnn.com</code> website.</p>
-
-<example>
-<Proxy http://cnn.com/*><br />
-Order allow,deny<br />
-Deny from all<br />
+that match the specified URL. For example, the following configuration
+will allow only a subset of clients to access the
+<code>www.example.com</code> website using the proxy server:</p>
+
+<highlight language="config">
+<Proxy http://www.example.com/*>
+ Require host yournetwork.example.com
</Proxy>
-</example>
+</highlight>
</section>
<section id="whatwhere"><title>What Directives are Allowed?</title>
<p>To find out what directives are allowed in what types of
configuration sections, check the <a
href="mod/directive-dict.html#Context">Context</a> of the directive.
-Everything that is allowed in
+Everything that is allowed in
<directive type="section" module="core">Directory</directive>
sections is also syntactically allowed in
<directive type="section" module="core">DirectoryMatch</directive>,
<directive type="section" module="core">LocationMatch</directive>,
<directive type="section" module="mod_proxy">Proxy</directive>,
and <directive type="section" module="mod_proxy">ProxyMatch</directive>
-sections. There are some exceptions, however.</p>
+sections. There are some exceptions, however:</p>
<ul>
<li>The <directive module="core">AllowOverride</directive> directive
</ul>
</section>
-<section id="mergin"><title>How the sections are merged</title>
+<section id="merging"><title>How the sections are merged</title>
<p>The configuration sections are applied in a very particular order.
Since this can have important effects on how configuration directives
<ol>
<li> <directive type="section"
module="core">Directory</directive> (except regular expressions)
- and .htaccess done simultaneously (with .htaccess, if allowed,
- overriding <directive type="section"
- module="core">Directory</directive>)</li>
+ and <code>.htaccess</code> done simultaneously (with
+ <code>.htaccess</code>, if allowed, overriding
+ <directive type="section" module="core">Directory</directive>)</li>
<li><directive type="section" module="core">DirectoryMatch</directive>
(and <code><Directory ~></code>)</li>
<li><directive type="section" module="core">Location</directive>
and <directive type="section"
module="core">LocationMatch</directive> done simultaneously</li>
+
+ <li><directive type="section" module="core">If</directive>
+ </li>
+
</ol>
<p>Apart from <directive type="section"
the order that they appear in the configuration files. <directive
type="section" module="core">Directory</directive> (group 1 above)
is processed in the order shortest directory component to longest.
- So for example, <code><Directory /var/web/dir></code> will
+ So for example, <code><Directory "/var/web/dir"></code> will
be processed before <code><Directory
- /var/web/dir/subdir></code>. If multiple <directive
+ "/var/web/dir/subdir"></code>. If multiple <directive
type="section" module="core">Directory</directive> sections apply
to the same directory they are processed in the configuration file
order. Configurations included via the <directive
the virtual host definition. This allows virtual hosts to
override the main server configuration.</p>
- <p>Later sections override earlier ones.</p>
+ <p>When the request is served by <module>mod_proxy</module>, the
+ <directive module="mod_proxy" type="section">Proxy</directive>
+ container takes the place of the <directive module="core"
+ type="section">Directory</directive> container in the processing
+ order.</p>
-<note><title>Technical Note</title>
+ <note><title>Technical Note</title>
There is actually a
<code><Location></code>/<code><LocationMatch></code>
sequence performed just before the name translation phase
are used to map URLs to filenames). The results of this
sequence are completely thrown away after the translation has
completed.
-</note>
+ </note>
+
+<section id="relationship-module-configuration"><title>Relationship between modules and configuration sections</title>
+ <p>One question that often arises after reading how configuration sections are
+ merged is related to how and when directives of specific modules like <module>mod_rewrite</module>
+ 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
+ <directive module="mod_headers">Header</directive> directive of <module>mod_headers</module> 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>
+ <highlight language="config">
+
+<Directory "/">
+ Header set CustomHeaderName one
+ <FilesMatch ".*">
+ Header set CustomHeaderName three
+ </FilesMatch>
+</Directory>
-<section id="merge-examples"><title>Some Examples</title>
+<Directory "/example">
+ Header set CustomHeaderName two
+</Directory>
+
+ </highlight>
+ <ul>
+ <li><directive>Directory</directive> "/" matches and an initial configuration to set the <code>CustomHeaderName</code> header with the value <code>one</code> is created.</li>
+ <li><directive>Directory</directive> "/example" matches, and since <module>mod_headers</module> 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><directive>FilesMatch</directive> ".*" 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 <module>mod_headers</module> will be called and it will receive the configuration to set the <code>CustomHeaderName</code> header with the value <code>three</code>. <module>mod_headers</module> 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 <directive>Directory</directive> in the merge order. The important concept to understand is that configuration sections like <directive>Directory</directive> and <directive>FilesMatch</directive> are not comparable to module specific directives like <directive module="mod_headers">Header</directive> or <directive module="mod_rewrite">RewriteRule</directive> because they operate on different levels.
+ </p>
+</section>
+
+<section id="merge-examples"><title>Some useful examples</title>
<p>Below is an artificial example to show the order of
merging. Assuming they all apply to the request, the directives in
this example will be applied in the order A > B > C > D >
E.</p>
-<example>
-<Location /><br />
-E<br />
-</Location><br />
-<br />
-<Files f.html><br />
-D<br />
-</Files><br />
-<br />
-<VirtualHost *><br />
-<Directory /a/b><br />
-B<br />
-</Directory><br />
-</VirtualHost><br />
-<br />
-<DirectoryMatch "^.*b$"><br />
-C<br />
-</DirectoryMatch><br />
-<br />
-<Directory /a/b><br />
-A<br />
-</Directory><br />
-<br />
-</example>
+<highlight language="config">
+<Location "/">
+ E
+</Location>
+
+<Files "f.html">
+ D
+</Files>
+
+<VirtualHost *>
+ <Directory "/a/">
+ B
+ </Directory>
+</VirtualHost>
+
+<DirectoryMatch "^.*b$">
+ C
+</DirectoryMatch>
+
+<Directory "/a/b">
+ A
+</Directory>
+
+</highlight>
+
<p>For a more concrete example, consider the following. Regardless of
any access restrictions placed in <directive module="core"
evaluated last and will allow unrestricted access to the server. In
other words, order of merging is important, so be careful!</p>
-<example>
-<Location /><br />
-Order deny,allow<br />
-Allow from all<br />
-</Location><br />
-<br />
-# Woops! This <Directory> section will have no effect<br />
-<Directory /><br />
-Order allow,deny<br />
-Allow from all<br />
-Deny from badguy.example.com<br />
+<highlight language="config">
+<Location "/">
+ Require all granted
+</Location>
+
+# Whoops! This <Directory> section will have no effect
+<Directory "/">
+ <RequireAll>
+ Require all granted
+ Require not host badguy.example.com
+ </RequireAll>
</Directory>
-</example>
+</highlight>
</section>
</section>
</manualpage>
-
projects / apache / blobdiff