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| <manualpage metafile="sections.xml.meta"> | |
| <title>Configuration Sections</title> | |
| <summary> <p>Directives in the <a | |
| href="configuring.html">configuration files</a> may apply to the | |
| entire server, or they may be restricted to apply only to particular | |
| directories, files, hosts, or URLs. This document describes how to | |
| use configuration section containers or <code>.htaccess</code> files | |
| to change the scope of other configuration directives.</p> | |
| </summary> | |
| <section id="types"><title>Types of Configuration Section Containers</title> | |
| <related> | |
| <modulelist> | |
| <module>core</module> | |
| <module>mod_version</module> | |
| <module>mod_proxy</module> | |
| </modulelist> | |
| <directivelist> | |
| <directive type="section" module="core">Directory</directive> | |
| <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" idtype="section" module="mod_md">MDomainSet</directive> | |
| <directive type="section" module="mod_proxy">Proxy</directive> | |
| <directive type="section" module="mod_proxy">ProxyMatch</directive> | |
| <directive type="section" module="core">VirtualHost</directive> | |
| </directivelist> | |
| </related> | |
| <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>, <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 <program>httpd</program> command line, | |
| or with a <directive module="core">Define</directive> directive. 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> | |
| <highlight language="config"> | |
| <IfDefine ClosedForNow> | |
| Redirect "/" "http://otherserver.example.com/" | |
| </IfDefine> | |
| </highlight> | |
| <p>The <directive type="section" module="core">IfModule</directive> | |
| directive is very similar, except it encloses directives that will | |
| only be applied if a particular module is available in the server. | |
| The module must either be statically compiled in the server, or it | |
| must be dynamically compiled and its <directive | |
| module="mod_so">LoadModule</directive> line must be earlier in the | |
| configuration file. This directive should only be used if you need | |
| your configuration file to work whether or not certain modules are | |
| installed. It should not be used to enclose directives that you want | |
| to work all the time, because it can suppress useful error messages | |
| about missing modules.</p> | |
| <p>In the following example, the <directive | |
| module="mod_mime_magic">MimeMagicFile</directive> directive will be | |
| applied only if <module>mod_mime_magic</module> is available.</p> | |
| <highlight language="config"> | |
| <IfModule mod_mime_magic.c> | |
| MimeMagicFile "conf/magic" | |
| </IfModule> | |
| </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, 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 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 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 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> | |
| <section id="filesystem"><title>Filesystem Containers</title> | |
| <p>The <directive type="section" module="core">Directory</directive> | |
| and <directive type="section" module="core">Files</directive> | |
| 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 (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> | |
| <highlight language="config"> | |
| <Directory "/var/web/dir1"> | |
| Options +Indexes | |
| </Directory> | |
| </highlight> | |
| <p>Directives enclosed in a <directive type="section" | |
| module="core">Files</directive> section apply to any file with | |
| the specified name, regardless of what directory it lies in. | |
| So for example, the following configuration directives will, | |
| when placed in the main section of the configuration file, | |
| deny access to any file named <code>private.html</code> regardless | |
| of where it is found.</p> | |
| <highlight language="config"> | |
| <Files "private.html"> | |
| Require all denied | |
| </Files> | |
| </highlight> | |
| <p>To address files found in a particular part of the filesystem, the | |
| <directive type="section" module="core">Files</directive> and | |
| <directive type="section" module="core">Directory</directive> sections | |
| can be combined. For example, the following configuration will deny | |
| access to <code>/var/web/dir1/private.html</code>, | |
| <code>/var/web/dir1/subdir2/private.html</code>, | |
| <code>/var/web/dir1/subdir3/private.html</code>, and any other instance | |
| of <code>private.html</code> found under the <code>/var/web/dir1/</code> | |
| directory.</p> | |
| <highlight language="config"> | |
| <Directory "/var/web/dir1"> | |
| <Files "private.html"> | |
| Require all denied | |
| </Files> | |
| </Directory> | |
| </highlight> | |
| </section> | |
| <section id="webspace"><title>Webspace Containers</title> | |
| <p>The <directive type="section" module="core">Location</directive> | |
| 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</code>, | |
| <code>http://yoursite.example.com/private123</code>, and | |
| <code>http://yoursite.example.com/private/dir/file.html</code> as well | |
| as any other requests starting with the <code>/private</code> string.</p> | |
| <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 handler provided by <module>mod_status</module>. | |
| No file called <code>server-status</code> needs to exist on the | |
| filesystem.</p> | |
| <highlight language="config"> | |
| # Map a URL to a built-in handler: | |
| <Location "/server-status"> | |
| SetHandler server-status | |
| </Location> | |
| # Map a URL path to a reverse proxy backend: | |
| <Location "/app"> | |
| ProxyPass "http://backend.example.com/" | |
| ProxyPassReverse "http://backend.example.com/" | |
| </Location> | |
| # Deny access to a URL path regardless of what serves it: | |
| <Location "/private"> | |
| Require all denied | |
| </Location> | |
| </highlight> | |
| <p>Because <directive type="section" module="core">Location</directive> | |
| operates on URLs rather than filesystem paths, it is the appropriate | |
| container for proxy configuration and module-provided endpoints.</p> | |
| </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> | |
| <p>The <directive type="section" module="core">Directory</directive>, | |
| <directive type="section" module="core">Files</directive>, and | |
| <directive type="section" module="core">Location</directive> | |
| directives can each use shell-style wildcard characters as in | |
| <code>fnmatch</code> from the C standard library. The character "*" | |
| matches any sequence of characters, "?" matches any single character, | |
| and "[<em>seq</em>]" matches any character in <em>seq</em>. The "/" | |
| character will not be matched by any wildcard; it must be specified | |
| explicitly.</p> | |
| <p>If even more flexible matching is required, each | |
| 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 | |
| <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> | |
| <highlight language="config"> | |
| <Directory "/home/*/public_html"> | |
| Options Indexes | |
| </Directory> | |
| </highlight> | |
| <p>Using regex sections, we can deny access to many types of image files | |
| at once:</p> | |
| <highlight language="config"> | |
| <FilesMatch "\.(?i:gif|jpe?g|png)$"> | |
| Require all denied | |
| </FilesMatch> | |
| </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> | |
| <section id="whichwhen"><title>What to use When</title> | |
| <p>Choosing between filesystem containers and webspace containers is | |
| actually quite easy. When applying directives to objects that reside | |
| in the filesystem always use <directive type="section" | |
| module="core">Directory</directive> or <directive type="section" | |
| module="core">Files</directive>. When applying directives to objects | |
| that do not reside in the filesystem (such as a webpage generated from | |
| a database), use <directive type="section" | |
| module="core">Location</directive>.</p> | |
| <p>It is important to never use <directive type="section" | |
| module="core">Location</directive> when trying to restrict | |
| access to objects in the filesystem. This is because many | |
| different webspace locations (URLs) could map to the same filesystem | |
| location, allowing your restrictions to be circumvented. | |
| For example, consider the following configuration:</p> | |
| <highlight language="config"> | |
| <Location "/dir/"> | |
| Require all denied | |
| </Location> | |
| </highlight> | |
| <p>This works fine if the request is for | |
| <code>http://yoursite.example.com/dir/</code>. But what if you are on | |
| a case-insensitive filesystem? Then your restriction could be easily | |
| circumvented by requesting | |
| <code>http://yoursite.example.com/DIR/</code>. The <directive | |
| type="section" module="core">Directory</directive> directive, in | |
| contrast, will apply to any content served from that location, | |
| regardless of how it is called. (An exception is filesystem links. | |
| The same directory can be placed in more than one part of the | |
| filesystem using symbolic links. The <directive type="section" | |
| module="core">Directory</directive> directive will follow the symbolic | |
| link without resetting the pathname. Therefore, for the highest level | |
| of security, symbolic links should be disabled with the appropriate | |
| <directive module="core">Options</directive> directive.)</p> | |
| <p>If you are, perhaps, thinking that none of this applies to you | |
| because you use a case-sensitive filesystem, remember that there are | |
| many other ways to map multiple webspace locations to the same | |
| 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 | |
| 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 (but not inside another | |
| <directive type="section" module="core">If</directive>). 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> | |
| <p>The <directive type="section" module="core">VirtualHost</directive> | |
| container encloses directives that apply to specific hosts. | |
| This is useful when serving multiple hosts from the same machine | |
| with a different configuration for each. For more information, | |
| see the <a href="vhosts/">Virtual Host Documentation</a>.</p> | |
| </section> | |
| <section id="proxy"><title>Proxy</title> | |
| <p>The <directive type="section" module="mod_proxy">Proxy</directive> | |
| 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 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> | |
| </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 | |
| <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">Files</directive>, | |
| <directive type="section" module="core">FilesMatch</directive>, | |
| <directive type="section" module="core">Location</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> | |
| <ul> | |
| <li>The <directive module="core">AllowOverride</directive> directive | |
| works only in <directive type="section" module="core">Directory</directive> | |
| sections.</li> | |
| <li>The <code>FollowSymLinks</code> and | |
| <code>SymLinksIfOwnerMatch</code> <directive | |
| module="core">Options</directive> work only in <directive | |
| type="section" module="core">Directory</directive> sections or | |
| <code>.htaccess</code> files.</li> | |
| <li>The <directive module="core">Options</directive> directive cannot | |
| be used in <directive type="section" module="core">Files</directive> | |
| and <directive type="section" module="core">FilesMatch</directive> | |
| sections.</li> | |
| </ul> | |
| </section> | |
| <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 | |
| are interpreted, it is important to understand how this works.</p> | |
| <p>The order of merging is:</p> | |
| <ol> | |
| <li> <directive type="section" | |
| module="core">Directory</directive> (except regular expressions) | |
| 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">Files</directive> and <directive | |
| type="section" module="core">FilesMatch</directive> done | |
| simultaneously</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> sections, even when | |
| they are enclosed in any of the preceding contexts. | |
| </li> | |
| </ol> | |
| <p>Some important remarks:</p> | |
| <ul> | |
| <li>Apart from <directive type="section" | |
| module="core">Directory</directive>, within each group the sections are | |
| processed in the order they appear in the configuration files. | |
| For example, a request for <em>/foo/bar</em> will match | |
| <code><Location "/foo/bar"></code> and | |
| <code><Location "/foo"></code> (group 4 in this case): | |
| both sections will be evaluated | |
| but in the order they appear in the configuration files.</li> | |
| <li><directive type="section" module="core">Directory</directive> | |
| (group 1 above) is processed in the order shortest directory | |
| component to longest (regardless of the order in which they | |
| appear in the configuration file). For example, | |
| <code><Directory "/var/web/dir"></code> will be processed before | |
| <code><Directory "/var/web/dir/subdir"></code>.</li> | |
| <li>If multiple <directive | |
| type="section" module="core">Directory</directive> sections apply | |
| to the same directory they are processed in the configuration file | |
| order. The same applies when multiple | |
| <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">Location</directive>, or | |
| <directive type="section" module="core">LocationMatch</directive> | |
| sections match the same resource.</li> | |
| <li>Configurations included via the <directive | |
| module="core">Include</directive> directive will be treated as if | |
| they were inside the including file at the location of the | |
| <directive module="core">Include</directive> directive.</li> | |
| <li>Sections inside <directive type="section" | |
| module="core">VirtualHost</directive> sections | |
| are applied <em>after</em> the corresponding sections outside | |
| the virtual host definition. This allows virtual hosts to | |
| override the main server configuration. Note that unlike the | |
| other section types, only one | |
| <directive type="section" module="core">VirtualHost</directive> | |
| is selected per request — directives from multiple matching | |
| vhosts are never merged. See | |
| <a href="vhosts/details.html">virtual host matching</a> | |
| for details on how a vhost is selected.</li> | |
| <li>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.</li> | |
| <li> Caution should be exercised when mixing related configuration | |
| directives inside and outside of <directive type="section" module="core" | |
| >If</directive> because of the effect on merging order. Explicit use | |
| of <directive type="section" module="core" >Else</directive> can help. | |
| </li> | |
| <li> When <directive type="section" module="core" >If</directive> is | |
| used in <code>.htaccess</code>, the enclosed directives in a parent | |
| directory will be merged <em>after</em> non-enclosed directives in a | |
| subdirectory.</li> | |
| <li><note type="warning"><title>Caution: <Limit> inside | |
| <Location> can silently grant access</title> | |
| <p>Using <directive type="section" module="core">Limit</directive> | |
| inside a <directive type="section" module="core">Location</directive> | |
| section to restrict authorization to specific HTTP methods can have | |
| unexpected results. For methods not listed in the | |
| <directive type="section" module="core">Limit</directive>, the | |
| enclosing <directive type="section" module="core">Location</directive> | |
| section is treated as having no authorization requirements — which | |
| effectively grants access and overrides any | |
| <directive type="section" module="core">Directory</directive> | |
| restrictions that would otherwise apply. Use | |
| <directive type="section" module="core">LimitExcept</directive> | |
| instead, or apply authorization without method restrictions.</p> | |
| </note></li> | |
| </ul> | |
| <note><title>Technical Note</title> | |
| There is actually a | |
| <code><Location></code>/<code><LocationMatch></code> | |
| sequence performed just before the name translation phase | |
| (where <code>Aliases</code> and <code>DocumentRoots</code> | |
| are used to map URLs to filenames). The results of this | |
| sequence are completely thrown away after the translation has | |
| completed. | |
| </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> | |
| <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 perform 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> | |
| <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" | |
| type="section">Directory</directive> sections, the <directive | |
| module="core" type="section">Location</directive> section will be | |
| evaluated last and will allow unrestricted access to the server. In | |
| other words, order of merging is important, so be careful!</p> | |
| <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> | |
| </highlight> | |
| </section> | |
| </section> | |
| </manualpage> |