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8 <title>Mapping URLs to Filesystem Locations - Apache HTTP Server</title>
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14 <p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p>
15 <p class="apache">Apache HTTP Server Version 2.1</p>
16 <img alt="" src="./images/feather.gif" /></div>
17 <div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div>
19 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="./">Version 2.1</a></div><div id="page-content"><div id="preamble"><h1>Mapping URLs to Filesystem Locations</h1>
21 <p><span>Available Languages: </span><a href="./en/urlmapping.html"> en </a> | <a href="./ja/urlmapping.html"> ja </a></p>
24 <p>This document explains how Apache uses the URL of a request
25 to determine the filesystem location from which to serve a
28 <div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#related">Related Modules and Directives</a></li>
29 <li><img alt="" src="./images/down.gif" /> <a href="#documentroot">DocumentRoot</a></li>
30 <li><img alt="" src="./images/down.gif" /> <a href="#outside">Files Outside the DocumentRoot</a></li>
31 <li><img alt="" src="./images/down.gif" /> <a href="#user">User Directories</a></li>
32 <li><img alt="" src="./images/down.gif" /> <a href="#redirect">URL Redirection</a></li>
33 <li><img alt="" src="./images/down.gif" /> <a href="#proxy">Reverse Proxy</a></li>
34 <li><img alt="" src="./images/down.gif" /> <a href="#rewrite">Rewriting Engine</a></li>
35 <li><img alt="" src="./images/down.gif" /> <a href="#notfound">File Not Found</a></li>
37 <div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
39 <h2><a name="related" id="related">Related Modules and Directives</a></h2>
41 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_alias.html">mod_alias</a></code></li><li><code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code></li><li><code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code></li><li><code class="module"><a href="./mod/mod_userdir.html">mod_userdir</a></code></li><li><code class="module"><a href="./mod/mod_speling.html">mod_speling</a></code></li><li><code class="module"><a href="./mod/mod_vhost_alias.html">mod_vhost_alias</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mod_alias.html#alias">Alias</a></code></li><li><code class="directive"><a href="./mod/mod_alias.html#aliasmatch">AliasMatch</a></code></li><li><code class="directive"><a href="./mod/mod_speling.html#checkspelling">CheckSpelling</a></code></li><li><code class="directive"><a href="./mod/core.html#documentroot">DocumentRoot</a></code></li><li><code class="directive"><a href="./mod/core.html#errordocument">ErrorDocument</a></code></li><li><code class="directive"><a href="./mod/core.html#options">Options</a></code></li><li><code class="directive"><a href="./mod/mod_proxy.html#proxypass">ProxyPass</a></code></li><li><code class="directive"><a href="./mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code></li><li><code class="directive"><a href="./mod/mod_alias.html#redirect">Redirect</a></code></li><li><code class="directive"><a href="./mod/mod_alias.html#redirectmatch">RedirectMatch</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewritecond">RewriteCond</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewritematch">RewriteMatch</a></code></li><li><code class="directive"><a href="./mod/mod_alias.html#scriptalias">ScriptAlias</a></code></li><li><code class="directive"><a href="./mod/mod_alias.html#scriptaliasmatch">ScriptAliasMatch</a></code></li><li><code class="directive"><a href="./mod/mod_userdir.html#userdir">UserDir</a></code></li></ul></td></tr></table>
42 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
44 <h2><a name="documentroot" id="documentroot">DocumentRoot</a></h2>
46 <p>In deciding what file to serve for a given request, Apache's
47 default behavior is to take the URL-Path for the request (the part
48 of the URL following the hostname and port) and add it to the end
49 of the <code class="directive"><a href="./mod/core.html#documentroot">DocumentRoot</a></code> specified
50 in your configuration files. Therefore, the files and directories
51 underneath the <code class="directive"><a href="./mod/core.html#documentroot">DocumentRoot</a></code>
52 make up the basic document tree which will be visible from the
55 <p>Apache is also capable of <a href="vhosts/">Virtual
56 Hosting</a>, where the server receives requests for more than one
57 host. In this case, a different <code class="directive"><a href="./mod/core.html#documentroot">DocumentRoot</a></code> can be specified for each
58 virtual host, or alternatively, the directives provided by the
59 module <code class="module"><a href="./mod/mod_vhost_alias.html">mod_vhost_alias</a></code> can
60 be used to dynamically determine the appropriate place from which
61 to serve content based on the requested IP address or
63 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
65 <h2><a name="outside" id="outside">Files Outside the DocumentRoot</a></h2>
67 <p>There are frequently circumstances where it is necessary to
68 allow web access to parts of the filesystem that are not strictly
69 underneath the <code class="directive"><a href="./mod/core.html#documentroot">DocumentRoot</a></code>. Apache offers several
70 different ways to accomplish this. On Unix systems, symbolic links
71 can bring other parts of the filesystem under the <code class="directive"><a href="./mod/core.html#documentroot">DocumentRoot</a></code>. For security reasons,
72 Apache will follow symbolic links only if the <code class="directive"><a href="./mod/core.html#options">Options</a></code> setting for the relevant
73 directory includes <code>FollowSymLinks</code> or
74 <code>SymLinksIfOwnerMatch</code>.</p>
76 <p>Alternatively, the <code class="directive"><a href="./mod/mod_alias.html#alias">Alias</a></code> directive will map any part
77 of the filesystem into the web space. For example, with</p>
79 <div class="example"><p><code>Alias /docs /var/web</code></p></div>
81 <p>the URL <code>http://www.example.com/docs/dir/file.html</code>
82 will be served from <code>/var/web/dir/file.html</code>. The
83 <code class="directive"><a href="./mod/mod_alias.html#scriptalias">ScriptAlias</a></code> directive
84 works the same way, with the additional effect that all content
85 located at the target path is treated as CGI scripts.</p>
87 <p>For situations where you require additional flexibility, you
88 can use the <code class="directive"><a href="./mod/mod_alias.html#aliasmatch">AliasMatch</a></code> and
89 <code class="directive"><a href="./mod/mod_alias.html#scriptaliasmatch">ScriptAliasMatch</a></code>
90 directives to do powerful regular-expression based matching and
91 substitution. For example,</p>
93 <div class="example"><p><code>ScriptAliasMatch ^/~([a-zA-Z0-9]*)/cgi-bin/(.*)
94 /home/$1/cgi-bin/$2</code></p></div>
96 <p>will map a request to
97 <code>http://example.com/~user/cgi-bin/script.cgi</code> to the
98 path <code>/home/user/cgi-bin/script.cgi</code> and will treat
99 the resulting file as a CGI script.</p>
100 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
101 <div class="section">
102 <h2><a name="user" id="user">User Directories</a></h2>
104 <p>Traditionally on Unix systems, the home directory of a
105 particular <em>user</em> can be referred to as
106 <code>~user/</code>. The module <code class="module"><a href="./mod/mod_userdir.html">mod_userdir</a></code>
107 extends this idea to the web by allowing files under each user's
108 home directory to be accessed using URLs such as the
111 <div class="example"><p><code>http://www.example.com/~user/file.html</code></p></div>
113 <p>For security reasons, it is inappropriate to give direct
114 access to a user's home directory from the web. Therefore, the
115 <code class="directive"><a href="./mod/mod_userdir.html#userdir">UserDir</a></code> directive
116 specifies a directory underneath the user's home directory
117 where web files are located. Using the default setting of
118 <code>Userdir public_html</code>, the above URL maps to a file
120 <code>/home/user/public_html/file.html</code> where
121 <code>/home/user/</code> is the user's home directory as
122 specified in <code>/etc/passwd</code>.</p>
124 <p>There are also several other forms of the
125 <code>Userdir</code> directive which you can use on systems
126 where <code>/etc/passwd</code> does not contain the location of
127 the home directory.</p>
129 <p>Some people find the "~" symbol (which is often encoded on the
130 web as <code>%7e</code>) to be awkward and prefer to use an
131 alternate string to represent user directories. This functionality
132 is not supported by mod_userdir. However, if users' home
133 directories are structured in a regular way, then it is possible
134 to use the <code class="directive"><a href="./mod/mod_alias.html#aliasmatch">AliasMatch</a></code>
135 directive to achieve the desired effect. For example, to make
136 <code>http://www.example.com/upages/user/file.html</code> map to
137 <code>/home/user/public_html/file.html</code>, use the following
138 <code>AliasMatch</code> directive:</p>
140 <div class="example"><p><code>AliasMatch ^/upages/([a-zA-Z0-9]*)/?(.*)
141 /home/$1/public_html/$2</code></p></div>
142 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
143 <div class="section">
144 <h2><a name="redirect" id="redirect">URL Redirection</a></h2>
146 <p>The configuration directives discussed in the above sections
147 tell Apache to get content from a specific place in the filesystem
148 and return it to the client. Sometimes, it is desirable instead to
149 inform the client that the requested content is located at a
150 different URL, and instruct the client to make a new request with
151 the new URL. This is called <em>redirection</em> and is
152 implemented by the <code class="directive"><a href="./mod/mod_alias.html#redirect">Redirect</a></code> directive. For example, if
153 the contents of the directory <code>/foo/</code> under the
154 <code class="directive"><a href="./mod/core.html#documentroot">DocumentRoot</a></code> are moved
155 to the new directory <code>/bar/</code>, you can instruct clients
156 to request the content at the new location as follows:</p>
158 <div class="example"><p><code>Redirect permanent /foo/
159 http://www.example.com/bar/</code></p></div>
161 <p>This will redirect any URL-Path starting in
162 <code>/foo/</code> to the same URL path on the
163 <code>www.example.com</code> server with <code>/bar/</code>
164 substituted for <code>/foo/</code>. You can redirect clients to
165 any server, not only the origin server.</p>
167 <p>Apache also provides a <code class="directive"><a href="./mod/mod_alias.html#redirectmatch">RedirectMatch</a></code> directive for more
168 complicated rewriting problems. For example, to redirect requests
169 for the site home page to a different site, but leave all other
170 requests alone, use the following configuration:</p>
172 <div class="example"><p><code>RedirectMatch permanent ^/$
173 http://www.example.com/startpage.html</code></p></div>
175 <p>Alternatively, to temporarily redirect all pages on one site
176 to a particular page on another site, use the following:</p>
178 <div class="example"><p><code>RedirectMatch temp .*
179 http://othersite.example.com/startpage.html</code></p></div>
180 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
181 <div class="section">
182 <h2><a name="proxy" id="proxy">Reverse Proxy</a></h2>
184 <p>Apache also allows you to bring remote documents into the URL space
185 of the local server. This technique is called <em>reverse
186 proxying</em> because the web server acts like a proxy server by
187 fetching the documents from a remote server and returning them to the
188 client. It is different from normal proxying because, to the client,
189 it appears the documents originate at the reverse proxy server.</p>
191 <p>In the following example, when clients request documents under the
192 <code>/foo/</code> directory, the server fetches those documents from
193 the <code>/bar/</code> directory on <code>internal.example.com</code>
194 and returns them to the client as if they were from the local
197 <div class="example"><p><code>
198 ProxyPass /foo/ http://internal.example.com/bar/<br />
199 ProxyPassReverse /foo/ http://internal.example.com/bar/
202 <p>The <code class="directive"><a href="./mod/mod_proxy.html#proxypass">ProxyPass</a></code> configures
203 the server to fetch the appropriate documents, while the
204 <code class="directive"><a href="./mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code>
205 directive rewrites redirects originating at
206 <code>internal.example.com</code> so that they target the appropriate
207 directory on the local server. It is important to note, however, that
208 links inside the documents will not be rewritten. So any absolute
209 links on <code>internal.example.com</code> will result in the client
210 breaking out of the proxy server and requesting directly from
211 <code>internal.example.com</code>.</p>
212 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
213 <div class="section">
214 <h2><a name="rewrite" id="rewrite">Rewriting Engine</a></h2>
216 <p>When even more powerful substitution is required, the rewriting
217 engine provided by <code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code>
218 can be useful. The directives provided by this module use
219 characteristics of the request such as browser type or source IP
220 address in deciding from where to serve content. In addition,
221 mod_rewrite can use external database files or programs to
222 determine how to handle a request. The rewriting engine is capable
223 of performing all three types of mappings discussed above:
224 internal redirects (aliases), external redirects, and proxying.
225 Many practical examples employing mod_rewrite are discussed in the
226 <a href="misc/rewriteguide.html">URL Rewriting Guide</a>.</p>
227 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
228 <div class="section">
229 <h2><a name="notfound" id="notfound">File Not Found</a></h2>
231 <p>Inevitably, URLs will be requested for which no matching
232 file can be found in the filesystem. This can happen for
233 several reasons. In some cases, it can be a result of moving
234 documents from one location to another. In this case, it is
235 best to use <a href="#redirect">URL redirection</a> to inform
236 clients of the new location of the resource. In this way, you
237 can assure that old bookmarks and links will continue to work,
238 even though the resource is at a new location.</p>
240 <p>Another common cause of "File Not Found" errors is
241 accidental mistyping of URLs, either directly in the browser,
242 or in HTML links. Apache provides the module
243 <code class="module"><a href="./mod/mod_speling.html">mod_speling</a></code> (sic) to help with
244 this problem. When this module is activated, it will intercept
245 "File Not Found" errors and look for a resource with a similar
246 filename. If one such file is found, mod_speling will send an
247 HTTP redirect to the client informing it of the correct
248 location. If several "close" files are found, a list of
249 available alternatives will be presented to the client.</p>
251 <p>An especially useful feature of mod_speling, is that it will
252 compare filenames without respect to case. This can help
253 systems where users are unaware of the case-sensitive nature of
254 URLs and the unix filesystem. But using mod_speling for
255 anything more than the occasional URL correction can place
256 additional load on the server, since each "incorrect" request
257 is followed by a URL redirection and a new request from the
260 <p>If all attempts to locate the content fail, Apache returns
261 an error page with HTTP status code 404 (file not found). The
262 appearance of this page is controlled with the
263 <code class="directive"><a href="./mod/core.html#errordocument">ErrorDocument</a></code> directive
264 and can be customized in a flexible manner as discussed in the
265 <a href="custom-error.html">Custom error responses</a>
268 <div class="bottomlang">
269 <p><span>Available Languages: </span><a href="./en/urlmapping.html"> en </a> | <a href="./ja/urlmapping.html"> ja </a></p>
270 </div><div id="footer">
271 <p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p>
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