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8 <title>core - Apache HTTP Server</title>
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15 <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>
16 <p class="apache">Apache HTTP Server Version 2.3</p>
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18 <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
20 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a> > <a href="./">Modules</a></div>
21 <div id="page-content">
22 <div id="preamble"><h1>Apache Core Features</h1>
24 <p><span>Available Languages: </span><a href="../de/mod/core.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
25 <a href="../en/mod/core.html" title="English"> en </a> |
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27 <a href="../ja/mod/core.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
28 <a href="../tr/mod/core.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p>
30 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Core Apache HTTP Server features that are always
32 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Core</td></tr></table>
34 <div id="quickview"><h3 class="directives">Directives</h3>
36 <li><img alt="" src="../images/down.gif" /> <a href="#acceptfilter">AcceptFilter</a></li>
37 <li><img alt="" src="../images/down.gif" /> <a href="#acceptpathinfo">AcceptPathInfo</a></li>
38 <li><img alt="" src="../images/down.gif" /> <a href="#accessfilename">AccessFileName</a></li>
39 <li><img alt="" src="../images/down.gif" /> <a href="#adddefaultcharset">AddDefaultCharset</a></li>
40 <li><img alt="" src="../images/down.gif" /> <a href="#addoutputfilterbytype">AddOutputFilterByType</a></li>
41 <li><img alt="" src="../images/down.gif" /> <a href="#allowencodedslashes">AllowEncodedSlashes</a></li>
42 <li><img alt="" src="../images/down.gif" /> <a href="#allowoverride">AllowOverride</a></li>
43 <li><img alt="" src="../images/down.gif" /> <a href="#cgimapextension">CGIMapExtension</a></li>
44 <li><img alt="" src="../images/down.gif" /> <a href="#contentdigest">ContentDigest</a></li>
45 <li><img alt="" src="../images/down.gif" /> <a href="#defaulttype">DefaultType</a></li>
46 <li><img alt="" src="../images/down.gif" /> <a href="#define">Define</a></li>
47 <li><img alt="" src="../images/down.gif" /> <a href="#directory"><Directory></a></li>
48 <li><img alt="" src="../images/down.gif" /> <a href="#directorymatch"><DirectoryMatch></a></li>
49 <li><img alt="" src="../images/down.gif" /> <a href="#documentroot">DocumentRoot</a></li>
50 <li><img alt="" src="../images/down.gif" /> <a href="#enablemmap">EnableMMAP</a></li>
51 <li><img alt="" src="../images/down.gif" /> <a href="#enablesendfile">EnableSendfile</a></li>
52 <li><img alt="" src="../images/down.gif" /> <a href="#errordocument">ErrorDocument</a></li>
53 <li><img alt="" src="../images/down.gif" /> <a href="#errorlog">ErrorLog</a></li>
54 <li><img alt="" src="../images/down.gif" /> <a href="#fileetag">FileETag</a></li>
55 <li><img alt="" src="../images/down.gif" /> <a href="#files"><Files></a></li>
56 <li><img alt="" src="../images/down.gif" /> <a href="#filesmatch"><FilesMatch></a></li>
57 <li><img alt="" src="../images/down.gif" /> <a href="#forcetype">ForceType</a></li>
58 <li><img alt="" src="../images/down.gif" /> <a href="#hostnamelookups">HostnameLookups</a></li>
59 <li><img alt="" src="../images/down.gif" /> <a href="#if"><If></a></li>
60 <li><img alt="" src="../images/down.gif" /> <a href="#ifdefine"><IfDefine></a></li>
61 <li><img alt="" src="../images/down.gif" /> <a href="#ifmodule"><IfModule></a></li>
62 <li><img alt="" src="../images/down.gif" /> <a href="#include">Include</a></li>
63 <li><img alt="" src="../images/down.gif" /> <a href="#keepalive">KeepAlive</a></li>
64 <li><img alt="" src="../images/down.gif" /> <a href="#keepalivetimeout">KeepAliveTimeout</a></li>
65 <li><img alt="" src="../images/down.gif" /> <a href="#limit"><Limit></a></li>
66 <li><img alt="" src="../images/down.gif" /> <a href="#limitexcept"><LimitExcept></a></li>
67 <li><img alt="" src="../images/down.gif" /> <a href="#limitinternalrecursion">LimitInternalRecursion</a></li>
68 <li><img alt="" src="../images/down.gif" /> <a href="#limitrequestbody">LimitRequestBody</a></li>
69 <li><img alt="" src="../images/down.gif" /> <a href="#limitrequestfields">LimitRequestFields</a></li>
70 <li><img alt="" src="../images/down.gif" /> <a href="#limitrequestfieldsize">LimitRequestFieldSize</a></li>
71 <li><img alt="" src="../images/down.gif" /> <a href="#limitrequestline">LimitRequestLine</a></li>
72 <li><img alt="" src="../images/down.gif" /> <a href="#limitxmlrequestbody">LimitXMLRequestBody</a></li>
73 <li><img alt="" src="../images/down.gif" /> <a href="#location"><Location></a></li>
74 <li><img alt="" src="../images/down.gif" /> <a href="#locationmatch"><LocationMatch></a></li>
75 <li><img alt="" src="../images/down.gif" /> <a href="#loglevel">LogLevel</a></li>
76 <li><img alt="" src="../images/down.gif" /> <a href="#maxkeepaliverequests">MaxKeepAliveRequests</a></li>
77 <li><img alt="" src="../images/down.gif" /> <a href="#mutex">Mutex</a></li>
78 <li><img alt="" src="../images/down.gif" /> <a href="#namevirtualhost">NameVirtualHost</a></li>
79 <li><img alt="" src="../images/down.gif" /> <a href="#options">Options</a></li>
80 <li><img alt="" src="../images/down.gif" /> <a href="#rlimitcpu">RLimitCPU</a></li>
81 <li><img alt="" src="../images/down.gif" /> <a href="#rlimitmem">RLimitMEM</a></li>
82 <li><img alt="" src="../images/down.gif" /> <a href="#rlimitnproc">RLimitNPROC</a></li>
83 <li><img alt="" src="../images/down.gif" /> <a href="#scriptinterpretersource">ScriptInterpreterSource</a></li>
84 <li><img alt="" src="../images/down.gif" /> <a href="#serveradmin">ServerAdmin</a></li>
85 <li><img alt="" src="../images/down.gif" /> <a href="#serveralias">ServerAlias</a></li>
86 <li><img alt="" src="../images/down.gif" /> <a href="#servername">ServerName</a></li>
87 <li><img alt="" src="../images/down.gif" /> <a href="#serverpath">ServerPath</a></li>
88 <li><img alt="" src="../images/down.gif" /> <a href="#serverroot">ServerRoot</a></li>
89 <li><img alt="" src="../images/down.gif" /> <a href="#serversignature">ServerSignature</a></li>
90 <li><img alt="" src="../images/down.gif" /> <a href="#servertokens">ServerTokens</a></li>
91 <li><img alt="" src="../images/down.gif" /> <a href="#sethandler">SetHandler</a></li>
92 <li><img alt="" src="../images/down.gif" /> <a href="#setinputfilter">SetInputFilter</a></li>
93 <li><img alt="" src="../images/down.gif" /> <a href="#setoutputfilter">SetOutputFilter</a></li>
94 <li><img alt="" src="../images/down.gif" /> <a href="#timeout">TimeOut</a></li>
95 <li><img alt="" src="../images/down.gif" /> <a href="#traceenable">TraceEnable</a></li>
96 <li><img alt="" src="../images/down.gif" /> <a href="#usecanonicalname">UseCanonicalName</a></li>
97 <li><img alt="" src="../images/down.gif" /> <a href="#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></li>
98 <li><img alt="" src="../images/down.gif" /> <a href="#virtualhost"><VirtualHost></a></li>
102 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
103 <div class="directive-section"><h2><a name="AcceptFilter" id="AcceptFilter">AcceptFilter</a> <a name="acceptfilter" id="acceptfilter">Directive</a></h2>
104 <table class="directive">
105 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures optimizations for a Protocol's Listener Sockets</td></tr>
106 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AcceptFilter <var>protocol</var> <var>accept_filter</var></code></td></tr>
107 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
108 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
109 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
110 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.1.5 and later.
111 On Windows from Apache 2.3.3 and later.</td></tr>
113 <p>This directive enables operating system specific optimizations for a
114 listening socket by the Protocol type. The basic premise is for the
115 kernel to not send a socket to the server process until either data
116 is received or an entire HTTP Request is buffered. Only
117 <a href="http://www.freebsd.org/cgi/man.cgi?query=accept_filter&sektion=9">
118 FreeBSD's Accept Filters</a>, Linux's more primitive
119 <code>TCP_DEFER_ACCEPT</code>, and Windows' optimized AcceptEx()
120 are currently supported.</p>
122 <p>Using <code>none</code> for an argument will disable any accept filters
123 for that protocol. This is useful for protocols that require a server
124 send data first, such as <code>ftp:</code> or <code>nntp</code>:</p>
125 <div class="example"><p><code>AcceptFilter nntp none</code></p></div>
127 <p>The default values on FreeBSD are:</p>
128 <div class="example"><p><code>
129 AcceptFilter http httpready <br />
130 AcceptFilter https dataready
133 <p>The <code>httpready</code> accept filter buffers entire HTTP requests at
134 the kernel level. Once an entire request is received, the kernel then
135 sends it to the server. See the
136 <a href="http://www.freebsd.org/cgi/man.cgi?query=accf_http&sektion=9">
137 accf_http(9)</a> man page for more details. Since HTTPS requests are
138 encrypted only the <a href="http://www.freebsd.org/cgi/man.cgi?query=accf_data&sektion=9">
139 accf_data(9)</a> filter is used.</p>
141 <p>The default values on Linux are:</p>
142 <div class="example"><p><code>
143 AcceptFilter http data <br />
144 AcceptFilter https data
147 <p>Linux's <code>TCP_DEFER_ACCEPT</code> does not support buffering http
148 requests. Any value besides <code>none</code> will enable
149 <code>TCP_DEFER_ACCEPT</code> on that listener. For more details
151 <a href="http://homepages.cwi.nl/~aeb/linux/man2html/man7/tcp.7.html">
152 tcp(7)</a> man page.</p>
154 <p>The default values on Windows are:</p>
155 <div class="example"><p><code>
156 AcceptFilter http data <br />
157 AcceptFilter https data
160 <p>Window's mpm_winnt interprets the AcceptFilter to toggle the AcceptEx()
161 API, and does not support http protocol buffering. There are two values
162 which utilize the Windows AcceptEx() API and will recycle network
163 sockets between connections. <code>data</code> waits until data has
164 been transmitted as documented above, and the initial data buffer and
165 network endpoint addresses are all retrieved from the single AcceptEx()
166 invocation. <code>connect</code> will use the AcceptEx() API, also
167 retrieve the network endpoint addresses, but like <code>none</code>
168 the <code>connect</code> option does not wait for the initial data
171 <p>On Windows, <code>none</code> uses accept() rather than than AcceptEx()
172 and will not recycle sockets between connections. This is useful for
173 network adapters with broken driver support, as well as some virtual
174 network providers such as vpn drivers, or spam, virus or spyware
179 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
180 <div class="directive-section"><h2><a name="AcceptPathInfo" id="AcceptPathInfo">AcceptPathInfo</a> <a name="acceptpathinfo" id="acceptpathinfo">Directive</a></h2>
181 <table class="directive">
182 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Resources accept trailing pathname information</td></tr>
183 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AcceptPathInfo On|Off|Default</code></td></tr>
184 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AcceptPathInfo Default</code></td></tr>
185 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
186 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
187 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
188 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
189 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.0.30 and later</td></tr>
192 <p>This directive controls whether requests that contain trailing
193 pathname information that follows an actual filename (or
194 non-existent file in an existing directory) will be accepted or
195 rejected. The trailing pathname information can be made
196 available to scripts in the <code>PATH_INFO</code> environment
199 <p>For example, assume the location <code>/test/</code> points to
200 a directory that contains only the single file
201 <code>here.html</code>. Then requests for
202 <code>/test/here.html/more</code> and
203 <code>/test/nothere.html/more</code> both collect
204 <code>/more</code> as <code>PATH_INFO</code>.</p>
206 <p>The three possible arguments for the
207 <code class="directive">AcceptPathInfo</code> directive are:</p>
209 <dt><code>Off</code></dt><dd>A request will only be accepted if it
210 maps to a literal path that exists. Therefore a request with
211 trailing pathname information after the true filename such as
212 <code>/test/here.html/more</code> in the above example will return
213 a 404 NOT FOUND error.</dd>
215 <dt><code>On</code></dt><dd>A request will be accepted if a
216 leading path component maps to a file that exists. The above
217 example <code>/test/here.html/more</code> will be accepted if
218 <code>/test/here.html</code> maps to a valid file.</dd>
220 <dt><code>Default</code></dt><dd>The treatment of requests with
221 trailing pathname information is determined by the <a href="../handler.html">handler</a> responsible for the request.
222 The core handler for normal files defaults to rejecting
223 <code>PATH_INFO</code> requests. Handlers that serve scripts, such as <a href="mod_cgi.html">cgi-script</a> and <a href="mod_isapi.html">isapi-handler</a>, generally accept
224 <code>PATH_INFO</code> by default.</dd>
227 <p>The primary purpose of the <code>AcceptPathInfo</code>
228 directive is to allow you to override the handler's choice of
229 accepting or rejecting <code>PATH_INFO</code>. This override is required,
230 for example, when you use a <a href="../filter.html">filter</a>, such
231 as <a href="mod_include.html">INCLUDES</a>, to generate content
232 based on <code>PATH_INFO</code>. The core handler would usually reject
233 the request, so you can use the following configuration to enable
236 <div class="example"><p><code>
237 <Files "mypaths.shtml"><br />
238 <span class="indent">
239 Options +Includes<br />
240 SetOutputFilter INCLUDES<br />
241 AcceptPathInfo On<br />
248 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
249 <div class="directive-section"><h2><a name="AccessFileName" id="AccessFileName">AccessFileName</a> <a name="accessfilename" id="accessfilename">Directive</a></h2>
250 <table class="directive">
251 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Name of the distributed configuration file</td></tr>
252 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AccessFileName <var>filename</var> [<var>filename</var>] ...</code></td></tr>
253 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AccessFileName .htaccess</code></td></tr>
254 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
255 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
256 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
258 <p>While processing a request the server looks for
259 the first existing configuration file from this list of names in
260 every directory of the path to the document, if distributed
261 configuration files are <a href="#allowoverride">enabled for that
262 directory</a>. For example:</p>
264 <div class="example"><p><code>
268 <p>before returning the document
269 <code>/usr/local/web/index.html</code>, the server will read
270 <code>/.acl</code>, <code>/usr/.acl</code>,
271 <code>/usr/local/.acl</code> and <code>/usr/local/web/.acl</code>
272 for directives, unless they have been disabled with</p>
274 <div class="example"><p><code>
275 <Directory /><br />
276 <span class="indent">
277 AllowOverride None<br />
284 <li><code class="directive"><a href="#allowoverride">AllowOverride</a></code></li>
285 <li><a href="../configuring.html">Configuration Files</a></li>
286 <li><a href="../howto/htaccess.html">.htaccess Files</a></li>
289 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
290 <div class="directive-section"><h2><a name="AddDefaultCharset" id="AddDefaultCharset">AddDefaultCharset</a> <a name="adddefaultcharset" id="adddefaultcharset">Directive</a></h2>
291 <table class="directive">
292 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default charset parameter to be added when a response
293 content-type is <code>text/plain</code> or <code>text/html</code></td></tr>
294 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AddDefaultCharset On|Off|<var>charset</var></code></td></tr>
295 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AddDefaultCharset Off</code></td></tr>
296 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
297 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
298 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
299 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
301 <p>This directive specifies a default value for the media type
302 charset parameter (the name of a character encoding) to be added
303 to a response if and only if the response's content-type is either
304 <code>text/plain</code> or <code>text/html</code>. This should override
305 any charset specified in the body of the response via a <code>META</code>
306 element, though the exact behavior is often dependent on the user's client
307 configuration. A setting of <code>AddDefaultCharset Off</code>
308 disables this functionality. <code>AddDefaultCharset On</code> enables
309 a default charset of <code>iso-8859-1</code>. Any other value is assumed
310 to be the <var>charset</var> to be used, which should be one of the
311 <a href="http://www.iana.org/assignments/character-sets">IANA registered
312 charset values</a> for use in Internet media types (MIME types).
315 <div class="example"><p><code>
316 AddDefaultCharset utf-8
319 <p><code class="directive">AddDefaultCharset</code> should only be used when all
320 of the text resources to which it applies are known to be in that
321 character encoding and it is too inconvenient to label their charset
322 individually. One such example is to add the charset parameter
323 to resources containing generated content, such as legacy CGI
324 scripts, that might be vulnerable to cross-site scripting attacks
325 due to user-provided data being included in the output. Note, however,
326 that a better solution is to just fix (or delete) those scripts, since
327 setting a default charset does not protect users that have enabled
328 the "auto-detect character encoding" feature on their browser.</p>
332 <li><code class="directive"><a href="../mod/mod_mime.html#addcharset">AddCharset</a></code></li>
335 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
336 <div class="directive-section"><h2><a name="AddOutputFilterByType" id="AddOutputFilterByType">AddOutputFilterByType</a> <a name="addoutputfilterbytype" id="addoutputfilterbytype">Directive</a></h2>
337 <table class="directive">
338 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>assigns an output filter to a particular media-type</td></tr>
339 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AddOutputFilterByType <var>filter</var>[;<var>filter</var>...]
340 <var>media-type</var> [<var>media-type</var>] ...</code></td></tr>
341 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
342 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
343 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
344 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
345 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.0.33 and later; deprecated in Apache 2.1 and later</td></tr>
347 <p>This directive activates a particular output <a href="../filter.html">filter</a> for a request depending on the
348 response <a class="glossarylink" href="../glossary.html#media-type" title="see glossary">media-type</a>. Because of certain
349 problems discussed below, this directive is deprecated. The same
350 functionality is available using <code class="module"><a href="../mod/mod_filter.html">mod_filter</a></code>.</p>
352 <p>The following example uses the <code>DEFLATE</code> filter, which
353 is provided by <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code>. It will compress all
354 output (either static or dynamic) which is labeled as
355 <code>text/html</code> or <code>text/plain</code> before it is sent
358 <div class="example"><p><code>
359 AddOutputFilterByType DEFLATE text/html text/plain
362 <p>If you want the content to be processed by more than one filter, their
363 names have to be separated by semicolons. It's also possible to use one
364 <code class="directive">AddOutputFilterByType</code> directive for each of
367 <p>The configuration below causes all script output labeled as
368 <code>text/html</code> to be processed at first by the
369 <code>INCLUDES</code> filter and then by the <code>DEFLATE</code>
372 <div class="example"><p><code>
373 <Location /cgi-bin/><br />
374 <span class="indent">
375 Options Includes<br />
376 AddOutputFilterByType INCLUDES;DEFLATE text/html<br />
381 <div class="warning"><h3>Note</h3>
382 <p>Enabling filters with <code class="directive">AddOutputFilterByType</code>
383 may fail partially or completely in some cases. For example, no
384 filters are applied if the <a class="glossarylink" href="../glossary.html#media-type" title="see glossary">media-type</a> could not
385 be determined. If you want to make sure that the filters will be
386 applied, assign the content type to a resource explicitly; for
387 example, with <code class="directive"><a href="../mod/mod_mime.html#addtype">AddType</a></code> or
388 <code class="directive"><a href="#forcetype">ForceType</a></code>. Setting the
389 content type within a (non-nph) CGI script is also safe.</p>
395 <li><code class="directive"><a href="../mod/mod_mime.html#addoutputfilter">AddOutputFilter</a></code></li>
396 <li><code class="directive"><a href="#setoutputfilter">SetOutputFilter</a></code></li>
397 <li><a href="../filter.html">filters</a></li>
400 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
401 <div class="directive-section"><h2><a name="AllowEncodedSlashes" id="AllowEncodedSlashes">AllowEncodedSlashes</a> <a name="allowencodedslashes" id="allowencodedslashes">Directive</a></h2>
402 <table class="directive">
403 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determines whether encoded path separators in URLs are allowed to
404 be passed through</td></tr>
405 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AllowEncodedSlashes On|Off</code></td></tr>
406 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AllowEncodedSlashes Off</code></td></tr>
407 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
408 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
409 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
410 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.0.46 and later</td></tr>
412 <p>The <code class="directive">AllowEncodedSlashes</code> directive allows URLs
413 which contain encoded path separators (<code>%2F</code> for <code>/</code>
414 and additionally <code>%5C</code> for <code>\</code> on according systems)
415 to be used. Normally such URLs are refused with a 404 (Not found) error.</p>
417 <p>Turning <code class="directive">AllowEncodedSlashes</code> <code>On</code> is
418 mostly useful when used in conjunction with <code>PATH_INFO</code>.</p>
420 <div class="note"><h3>Note</h3>
421 <p>Allowing encoded slashes does <em>not</em> imply <em>decoding</em>.
422 Occurrences of <code>%2F</code> or <code>%5C</code> (<em>only</em> on
423 according systems) will be left as such in the otherwise decoded URL
429 <li><code class="directive"><a href="#acceptpathinfo">AcceptPathInfo</a></code></li>
432 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
433 <div class="directive-section"><h2><a name="AllowOverride" id="AllowOverride">AllowOverride</a> <a name="allowoverride" id="allowoverride">Directive</a></h2>
434 <table class="directive">
435 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Types of directives that are allowed in
436 <code>.htaccess</code> files</td></tr>
437 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AllowOverride All|None|<var>directive-type</var>
438 [<var>directive-type</var>] ...</code></td></tr>
439 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AllowOverride All</code></td></tr>
440 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory</td></tr>
441 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
442 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
444 <p>When the server finds an <code>.htaccess</code> file (as
445 specified by <code class="directive"><a href="#accessfilename">AccessFileName</a></code>)
446 it needs to know which directives declared in that file can override
447 earlier configuration directives.</p>
449 <div class="note"><h3>Only available in <Directory> sections</h3>
450 <code class="directive">AllowOverride</code> is valid only in
451 <code class="directive"><a href="#directory"><Directory></a></code>
452 sections specified without regular expressions, not in <code class="directive"><a href="#location"><Location></a></code>, <code class="directive"><a href="#directorymatch"><DirectoryMatch></a></code> or
453 <code class="directive"><a href="#files"><Files></a></code> sections.
456 <p>When this directive is set to <code>None</code>, then
457 <a href="#accessfilename">.htaccess</a> files are completely ignored.
458 In this case, the server will not even attempt to read
459 <code>.htaccess</code> files in the filesystem.</p>
461 <p>When this directive is set to <code>All</code>, then any
462 directive which has the .htaccess <a href="directive-dict.html#Context">Context</a> is allowed in
463 <code>.htaccess</code> files.</p>
465 <p>The <var>directive-type</var> can be one of the following
466 groupings of directives.</p>
473 Allow use of the authorization directives (<code class="directive"><a href="../mod/mod_authn_dbm.html#authdbmgroupfile">AuthDBMGroupFile</a></code>,
474 <code class="directive"><a href="../mod/mod_authn_dbm.html#authdbmuserfile">AuthDBMUserFile</a></code>,
475 <code class="directive"><a href="../mod/mod_authz_groupfile.html#authgroupfile">AuthGroupFile</a></code>,
476 <code class="directive"><a href="../mod/mod_authn_core.html#authname">AuthName</a></code>,
477 <code class="directive"><a href="../mod/mod_authn_core.html#authtype">AuthType</a></code>, <code class="directive"><a href="../mod/mod_authn_file.html#authuserfile">AuthUserFile</a></code>, <code class="directive"><a href="../mod/mod_authz_core.html#require">Require</a></code>, <em>etc.</em>).</dd>
482 Allow use of the directives controlling document types
483 (<code class="directive"><a href="#errordocument">ErrorDocument</a></code>,
484 <code class="directive"><a href="#forcetype">ForceType</a></code>,
485 <code class="directive"><a href="../mod/mod_negotiation.html#languagepriority">LanguagePriority</a></code>,
486 <code class="directive"><a href="#sethandler">SetHandler</a></code>,
487 <code class="directive"><a href="#setinputfilter">SetInputFilter</a></code>,
488 <code class="directive"><a href="#setoutputfilter">SetOutputFilter</a></code>, and
489 <code class="module"><a href="../mod/mod_mime.html">mod_mime</a></code> Add* and Remove* directives),
490 document meta data (<code class="directive"><a href="../mod/mod_headers.html#header">Header</a></code>, <code class="directive"><a href="../mod/mod_headers.html#requestheader">RequestHeader</a></code>, <code class="directive"><a href="../mod/mod_setenvif.html#setenvif">SetEnvIf</a></code>, <code class="directive"><a href="../mod/mod_setenvif.html#setenvifnocase">SetEnvIfNoCase</a></code>, <code class="directive"><a href="../mod/mod_setenvif.html#browsermatch">BrowserMatch</a></code>, <code class="directive"><a href="../mod/mod_usertrack.html#cookieexpires">CookieExpires</a></code>, <code class="directive"><a href="../mod/mod_usertrack.html#cookiedomain">CookieDomain</a></code>, <code class="directive"><a href="../mod/mod_usertrack.html#cookiestyle">CookieStyle</a></code>, <code class="directive"><a href="../mod/mod_usertrack.html#cookietracking">CookieTracking</a></code>, <code class="directive"><a href="../mod/mod_usertrack.html#cookiename">CookieName</a></code>),
491 <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> directives <code class="directive"><a href="../mod/mod_rewrite.html#rewriteengine">RewriteEngine</a></code>, <code class="directive"><a href="../mod/mod_rewrite.html#rewriteoptions">RewriteOptions</a></code>, <code class="directive"><a href="../mod/mod_rewrite.html#rewritebase">RewriteBase</a></code>, <code class="directive"><a href="../mod/mod_rewrite.html#rewritecond">RewriteCond</a></code>, <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>) and
492 <code class="directive"><a href="../mod/mod_actions.html#action">Action</a></code> from
493 <code class="module"><a href="../mod/mod_actions.html">mod_actions</a></code>.
499 Allow use of the directives controlling directory indexing
500 (<code class="directive"><a href="../mod/mod_autoindex.html#adddescription">AddDescription</a></code>,
501 <code class="directive"><a href="../mod/mod_autoindex.html#addicon">AddIcon</a></code>, <code class="directive"><a href="../mod/mod_autoindex.html#addiconbyencoding">AddIconByEncoding</a></code>,
502 <code class="directive"><a href="../mod/mod_autoindex.html#addiconbytype">AddIconByType</a></code>,
503 <code class="directive"><a href="../mod/mod_autoindex.html#defaulticon">DefaultIcon</a></code>, <code class="directive"><a href="../mod/mod_dir.html#directoryindex">DirectoryIndex</a></code>, <code class="directive"><a href="../mod/mod_autoindex.html#fancyindexing">FancyIndexing</a></code>, <code class="directive"><a href="../mod/mod_autoindex.html#headername">HeaderName</a></code>, <code class="directive"><a href="../mod/mod_autoindex.html#indexignore">IndexIgnore</a></code>, <code class="directive"><a href="../mod/mod_autoindex.html#indexoptions">IndexOptions</a></code>, <code class="directive"><a href="../mod/mod_autoindex.html#readmename">ReadmeName</a></code>,
509 Allow use of the directives controlling host access (<code class="directive"><a href="../mod/mod_authz_host.html#allow">Allow</a></code>, <code class="directive"><a href="../mod/mod_authz_host.html#deny">Deny</a></code> and <code class="directive"><a href="../mod/mod_authz_host.html#order">Order</a></code>).</dd>
511 <dt>Options[=<var>Option</var>,...]</dt>
514 Allow use of the directives controlling specific directory
515 features (<code class="directive"><a href="#options">Options</a></code> and
516 <code class="directive"><a href="../mod/mod_include.html#xbithack">XBitHack</a></code>).
517 An equal sign may be given followed by a comma (but no spaces)
518 separated lists of options that may be set using the <code class="directive"><a href="#options">Options</a></code> command.</dd>
523 <div class="example"><p><code>
524 AllowOverride AuthConfig Indexes
527 <p>In the example above all directives that are neither in the group
528 <code>AuthConfig</code> nor <code>Indexes</code> cause an internal
531 <div class="note"><p>For security and performance reasons, do not set
532 <code>AllowOverride</code> to anything other than <code>None</code>
533 in your <code><Directory /></code> block. Instead, find (or
534 create) the <code><Directory></code> block that refers to the
535 directory where you're actually planning to place a
536 <code>.htaccess</code> file.</p>
541 <li><code class="directive"><a href="#accessfilename">AccessFileName</a></code></li>
542 <li><a href="../configuring.html">Configuration Files</a></li>
543 <li><a href="../howto/htaccess.html">.htaccess Files</a></li>
546 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
547 <div class="directive-section"><h2><a name="CGIMapExtension" id="CGIMapExtension">CGIMapExtension</a> <a name="cgimapextension" id="cgimapextension">Directive</a></h2>
548 <table class="directive">
549 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Technique for locating the interpreter for CGI
551 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CGIMapExtension <var>cgi-path</var> <var>.extension</var></code></td></tr>
552 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
553 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
554 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
555 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
556 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>NetWare only</td></tr>
558 <p>This directive is used to control how Apache finds the
559 interpreter used to run CGI scripts. For example, setting
560 <code>CGIMapExtension sys:\foo.nlm .foo</code> will
561 cause all CGI script files with a <code>.foo</code> extension to
562 be passed to the FOO interpreter.</p>
565 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
566 <div class="directive-section"><h2><a name="ContentDigest" id="ContentDigest">ContentDigest</a> <a name="contentdigest" id="contentdigest">Directive</a></h2>
567 <table class="directive">
568 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables the generation of <code>Content-MD5</code> HTTP Response
570 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ContentDigest On|Off</code></td></tr>
571 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ContentDigest Off</code></td></tr>
572 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
573 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Options</td></tr>
574 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
575 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
577 <p>This directive enables the generation of
578 <code>Content-MD5</code> headers as defined in RFC1864
579 respectively RFC2616.</p>
581 <p>MD5 is an algorithm for computing a "message digest"
582 (sometimes called "fingerprint") of arbitrary-length data, with
583 a high degree of confidence that any alterations in the data
584 will be reflected in alterations in the message digest.</p>
586 <p>The <code>Content-MD5</code> header provides an end-to-end
587 message integrity check (MIC) of the entity-body. A proxy or
588 client may check this header for detecting accidental
589 modification of the entity-body in transit. Example header:</p>
591 <div class="example"><p><code>
592 Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==
595 <p>Note that this can cause performance problems on your server
596 since the message digest is computed on every request (the
597 values are not cached).</p>
599 <p><code>Content-MD5</code> is only sent for documents served
600 by the <code class="module"><a href="../mod/core.html">core</a></code>, and not by any module. For example,
601 SSI documents, output from CGI scripts, and byte range responses
602 do not have this header.</p>
605 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
606 <div class="directive-section"><h2><a name="DefaultType" id="DefaultType">DefaultType</a> <a name="defaulttype" id="defaulttype">Directive</a></h2>
607 <table class="directive">
608 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>This directive has no effect other than to emit warnings
609 if the value is not <code>none</code>. In prior versions, DefaultType
610 would specify a default media type to assign to response content for
611 which no other media type configuration could be found.
613 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DefaultType <var>media-type|none</var></code></td></tr>
614 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DefaultType none</code></td></tr>
615 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
616 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
617 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
618 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
619 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The argument <code>none</code> is available in Apache 2.2.7 and later. All other choices are DISABLED for 2.3.x and later.</td></tr>
621 <p>This directive has been disabled. For backwards compatibility
622 of configuration files, it may be specified with the value
623 <code>none</code>, meaning no default media type. For example:</p>
625 <div class="example"><p><code>
629 <p><code>DefaultType None</code> is only available in
630 httpd-2.2.7 and later.</p>
632 <p>Use the mime.types configuration file and the
633 <code class="directive"><a href="../mod/mod_mime.html#addtype">AddType</a></code> to configure media
634 type assignments via file extensions, or the
635 <code class="directive"><a href="#forcetype">ForceType</a></code> directive to configure
636 the media type for specific resources. Otherwise, the server will
637 send the response without a Content-Type header field and the
638 recipient may attempt to guess the media type.</p>
641 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
642 <div class="directive-section"><h2><a name="Define" id="Define">Define</a> <a name="define" id="define">Directive</a></h2>
643 <table class="directive">
644 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Define the existence of a variable</td></tr>
645 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Define <var>parameter-name</var></code></td></tr>
646 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
647 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
648 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
650 <p>Equivalent to passing the <code>-D</code> argument to <code class="program"><a href="../programs/httpd.html">httpd</a></code>.</p>
651 <p>This directive can be used to toggle the use of <code class="directive"><a href="#ifdefine"><IfDefine></a></code> sections without needing to alter
652 <code>-D</code> arguments in any startup scripts.</p>
655 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
656 <div class="directive-section"><h2><a name="Directory" id="Directory"><Directory></a> <a name="directory" id="directory">Directive</a></h2>
657 <table class="directive">
658 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enclose a group of directives that apply only to the
659 named file-system directory and sub-directories</td></tr>
660 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><Directory <var>directory-path</var>>
661 ... </Directory></code></td></tr>
662 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
663 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
664 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
666 <p><code class="directive"><Directory></code> and
667 <code></Directory></code> are used to enclose a group of
668 directives that will apply only to the named directory and
669 sub-directories of that directory. Any directive that is allowed
670 in a directory context may be used. <var>Directory-path</var> is
671 either the full path to a directory, or a wild-card string using
672 Unix shell-style matching. In a wild-card string, <code>?</code> matches
673 any single character, and <code>*</code> matches any sequences of
674 characters. You may also use <code>[]</code> character ranges. None
675 of the wildcards match a `/' character, so <code><Directory
676 /*/public_html></code> will not match
677 <code>/home/user/public_html</code>, but <code><Directory
678 /home/*/public_html></code> will match. Example:</p>
680 <div class="example"><p><code>
681 <Directory /usr/local/httpd/htdocs><br />
682 <span class="indent">
683 Options Indexes FollowSymLinks<br />
689 <p>Be careful with the <var>directory-path</var> arguments:
690 They have to literally match the filesystem path which Apache uses
691 to access the files. Directives applied to a particular
692 <code><Directory></code> will not apply to files accessed from
693 that same directory via a different path, such as via different symbolic
697 <p><a class="glossarylink" href="../glossary.html#regex" title="see glossary">Regular
698 expressions</a> can also be used, with the addition of the
699 <code>~</code> character. For example:</p>
701 <div class="example"><p><code>
702 <Directory ~ "^/www/.*/[0-9]{3}">
705 <p>would match directories in <code>/www/</code> that consisted of
708 <p>If multiple (non-regular expression) <code class="directive"><Directory></code> sections
709 match the directory (or one of its parents) containing a document,
710 then the directives are applied in the order of shortest match
711 first, interspersed with the directives from the <a href="#accessfilename">.htaccess</a> files. For example,
714 <div class="example"><p><code>
715 <Directory /><br />
716 <span class="indent">
717 AllowOverride None<br />
719 </Directory><br />
721 <Directory /home/><br />
722 <span class="indent">
723 AllowOverride FileInfo<br />
728 <p>for access to the document <code>/home/web/dir/doc.html</code>
732 <li>Apply directive <code>AllowOverride None</code>
733 (disabling <code>.htaccess</code> files).</li>
735 <li>Apply directive <code>AllowOverride FileInfo</code> (for
736 directory <code>/home</code>).</li>
738 <li>Apply any <code>FileInfo</code> directives in
739 <code>/home/.htaccess</code>, <code>/home/web/.htaccess</code> and
740 <code>/home/web/dir/.htaccess</code> in that order.</li>
743 <p>Regular expressions are not considered until after all of the
744 normal sections have been applied. Then all of the regular
745 expressions are tested in the order they appeared in the
746 configuration file. For example, with</p>
748 <div class="example"><p><code>
749 <Directory ~ abc$><br />
750 <span class="indent">
751 # ... directives here ...<br />
756 <p>the regular expression section won't be considered until after
757 all normal <code class="directive"><Directory></code>s and
758 <code>.htaccess</code> files have been applied. Then the regular
759 expression will match on <code>/home/abc/public_html/abc</code> and
760 the corresponding <code class="directive"><Directory></code> will
763 <p><strong>Note that the default Apache access for
764 <code><Directory /></code> is <code>Allow from All</code>.
765 This means that Apache will serve any file mapped from an URL. It is
766 recommended that you change this with a block such
769 <div class="example"><p><code>
770 <Directory /><br />
771 <span class="indent">
772 Order Deny,Allow<br />
778 <p><strong>and then override this for directories you
779 <em>want</em> accessible. See the <a href="../misc/security_tips.html">Security Tips</a> page for more
780 details.</strong></p>
782 <p>The directory sections occur in the <code>httpd.conf</code> file.
783 <code class="directive"><Directory></code> directives
784 cannot nest, and cannot appear in a <code class="directive"><a href="#limit"><Limit></a></code> or <code class="directive"><a href="#limitexcept"><LimitExcept></a></code> section.</p>
788 <li><a href="../sections.html">How <Directory>,
789 <Location> and <Files> sections work</a> for an
790 explanation of how these different sections are combined when a
791 request is received</li>
794 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
795 <div class="directive-section"><h2><a name="DirectoryMatch" id="DirectoryMatch"><DirectoryMatch></a> <a name="directorymatch" id="directorymatch">Directive</a></h2>
796 <table class="directive">
797 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enclose directives that apply to
798 file-system directories matching a regular expression and their
799 subdirectories</td></tr>
800 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><DirectoryMatch <var>regex</var>>
801 ... </DirectoryMatch></code></td></tr>
802 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
803 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
804 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
806 <p><code class="directive"><DirectoryMatch></code> and
807 <code></DirectoryMatch></code> are used to enclose a group
808 of directives which will apply only to the named directory and
809 sub-directories of that directory, the same as <code class="directive"><a href="#directory"><Directory></a></code>. However, it
810 takes as an argument a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular
811 expression</a>. For example:</p>
813 <div class="example"><p><code>
814 <DirectoryMatch "^/www/(.+/)?[0-9]{3}">
817 <p>would match directories in <code>/www/</code> that consisted of three
822 <li><code class="directive"><a href="#directory"><Directory></a></code> for
823 a description of how regular expressions are mixed in with normal
824 <code class="directive"><Directory></code>s</li>
825 <li><a href="../sections.html">How <Directory>, <Location> and
826 <Files> sections work</a> for an explanation of how these different
827 sections are combined when a request is received</li>
830 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
831 <div class="directive-section"><h2><a name="DocumentRoot" id="DocumentRoot">DocumentRoot</a> <a name="documentroot" id="documentroot">Directive</a></h2>
832 <table class="directive">
833 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory that forms the main document tree visible
834 from the web</td></tr>
835 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DocumentRoot <var>directory-path</var></code></td></tr>
836 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DocumentRoot /usr/local/apache/htdocs</code></td></tr>
837 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
838 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
839 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
841 <p>This directive sets the directory from which <code class="program"><a href="../programs/httpd.html">httpd</a></code>
842 will serve files. Unless matched by a directive like <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code>, the server appends the
843 path from the requested URL to the document root to make the
844 path to the document. Example:</p>
846 <div class="example"><p><code>
847 DocumentRoot /usr/web
851 <code>http://www.my.host.com/index.html</code> refers to
852 <code>/usr/web/index.html</code>. If the <var>directory-path</var> is
853 not absolute then it is assumed to be relative to the <code class="directive"><a href="#serverroot">ServerRoot</a></code>.</p>
855 <p>The <code class="directive">DocumentRoot</code> should be specified without
856 a trailing slash.</p>
860 <li><a href="../urlmapping.html#documentroot">Mapping URLs to Filesystem
864 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
865 <div class="directive-section"><h2><a name="EnableMMAP" id="EnableMMAP">EnableMMAP</a> <a name="enablemmap" id="enablemmap">Directive</a></h2>
866 <table class="directive">
867 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Use memory-mapping to read files during delivery</td></tr>
868 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableMMAP On|Off</code></td></tr>
869 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableMMAP On</code></td></tr>
870 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
871 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
872 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
873 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
875 <p>This directive controls whether the <code class="program"><a href="../programs/httpd.html">httpd</a></code> may use
876 memory-mapping if it needs to read the contents of a file during
877 delivery. By default, when the handling of a request requires
878 access to the data within a file -- for example, when delivering a
879 server-parsed file using <code class="module"><a href="../mod/mod_include.html">mod_include</a></code> -- Apache
880 memory-maps the file if the OS supports it.</p>
882 <p>This memory-mapping sometimes yields a performance improvement.
883 But in some environments, it is better to disable the memory-mapping
884 to prevent operational problems:</p>
887 <li>On some multiprocessor systems, memory-mapping can reduce the
888 performance of the <code class="program"><a href="../programs/httpd.html">httpd</a></code>.</li>
889 <li>Deleting or truncating a file while <code class="program"><a href="../programs/httpd.html">httpd</a></code>
890 has it memory-mapped can cause <code class="program"><a href="../programs/httpd.html">httpd</a></code> to
891 crash with a segmentation fault.
895 <p>For server configurations that are vulnerable to these problems,
896 you should disable memory-mapping of delivered files by specifying:</p>
898 <div class="example"><p><code>
902 <p>For NFS mounted files, this feature may be disabled explicitly for
903 the offending files by specifying:</p>
905 <div class="example"><p><code>
906 <Directory "/path-to-nfs-files">
907 <span class="indent">
914 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
915 <div class="directive-section"><h2><a name="EnableSendfile" id="EnableSendfile">EnableSendfile</a> <a name="enablesendfile" id="enablesendfile">Directive</a></h2>
916 <table class="directive">
917 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Use the kernel sendfile support to deliver files to the client</td></tr>
918 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableSendfile On|Off</code></td></tr>
919 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableSendfile On</code></td></tr>
920 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
921 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
922 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
923 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
924 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.44 and later</td></tr>
926 <p>This directive controls whether <code class="program"><a href="../programs/httpd.html">httpd</a></code> may use the
927 sendfile support from the kernel to transmit file contents to the client.
928 By default, when the handling of a request requires no access
929 to the data within a file -- for example, when delivering a
930 static file -- Apache uses sendfile to deliver the file contents
931 without ever reading the file if the OS supports it.</p>
933 <p>This sendfile mechanism avoids separate read and send operations,
934 and buffer allocations. But on some platforms or within some
935 filesystems, it is better to disable this feature to avoid
936 operational problems:</p>
939 <li>Some platforms may have broken sendfile support that the build
940 system did not detect, especially if the binaries were built on
941 another box and moved to such a machine with broken sendfile
943 <li>On Linux the use of sendfile triggers TCP-checksum
944 offloading bugs on certain networking cards when using IPv6.</li>
945 <li>On Linux on Itanium, sendfile may be unable to handle files
946 over 2GB in size.</li>
947 <li>With a network-mounted <code class="directive"><a href="#documentroot">DocumentRoot</a></code> (e.g., NFS or SMB),
948 the kernel may be unable to serve the network file through
952 <p>For server configurations that are vulnerable to these problems,
953 you should disable this feature by specifying:</p>
955 <div class="example"><p><code>
959 <p>For NFS or SMB mounted files, this feature may be disabled explicitly
960 for the offending files by specifying:</p>
962 <div class="example"><p><code>
963 <Directory "/path-to-nfs-files">
964 <span class="indent">
969 <p>Please note that the per-directory and .htaccess configuration
970 of <code class="directive">EnableSendfile</code> is not supported by
971 <code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code>.
972 Only global definition of <code class="directive">EnableSendfile</code>
973 is taken into account by the module.
977 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
978 <div class="directive-section"><h2><a name="ErrorDocument" id="ErrorDocument">ErrorDocument</a> <a name="errordocument" id="errordocument">Directive</a></h2>
979 <table class="directive">
980 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>What the server will return to the client
981 in case of an error</td></tr>
982 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ErrorDocument <var>error-code</var> <var>document</var></code></td></tr>
983 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
984 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
985 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
986 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
987 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Quoting syntax for text messages is different in Apache
990 <p>In the event of a problem or error, Apache can be configured
991 to do one of four things,</p>
994 <li>output a simple hardcoded error message</li>
996 <li>output a customized message</li>
998 <li>redirect to a local <var>URL-path</var> to handle the
1001 <li>redirect to an external <var>URL</var> to handle the
1005 <p>The first option is the default, while options 2-4 are
1006 configured using the <code class="directive">ErrorDocument</code>
1007 directive, which is followed by the HTTP response code and a URL
1008 or a message. Apache will sometimes offer additional information
1009 regarding the problem/error.</p>
1011 <p>URLs can begin with a slash (/) for local web-paths (relative
1012 to the <code class="directive"><a href="#documentroot">DocumentRoot</a></code>), or be a
1013 full URL which the client can resolve. Alternatively, a message
1014 can be provided to be displayed by the browser. Examples:</p>
1016 <div class="example"><p><code>
1017 ErrorDocument 500 http://foo.example.com/cgi-bin/tester<br />
1018 ErrorDocument 404 /cgi-bin/bad_urls.pl<br />
1019 ErrorDocument 401 /subscription_info.html<br />
1020 ErrorDocument 403 "Sorry can't allow you access today"
1023 <p>Additionally, the special value <code>default</code> can be used
1024 to specify Apache's simple hardcoded message. While not required
1025 under normal circumstances, <code>default</code> will restore
1026 Apache's simple hardcoded message for configurations that would
1027 otherwise inherit an existing <code class="directive">ErrorDocument</code>.</p>
1029 <div class="example"><p><code>
1030 ErrorDocument 404 /cgi-bin/bad_urls.pl<br /><br />
1031 <Directory /web/docs><br />
1032 <span class="indent">
1033 ErrorDocument 404 default<br />
1038 <p>Note that when you specify an <code class="directive">ErrorDocument</code>
1039 that points to a remote URL (ie. anything with a method such as
1040 <code>http</code> in front of it), Apache will send a redirect to the
1041 client to tell it where to find the document, even if the
1042 document ends up being on the same server. This has several
1043 implications, the most important being that the client will not
1044 receive the original error status code, but instead will
1045 receive a redirect status code. This in turn can confuse web
1046 robots and other clients which try to determine if a URL is
1047 valid using the status code. In addition, if you use a remote
1048 URL in an <code>ErrorDocument 401</code>, the client will not
1049 know to prompt the user for a password since it will not
1050 receive the 401 status code. Therefore, <strong>if you use an
1051 <code>ErrorDocument 401</code> directive then it must refer to a local
1052 document.</strong></p>
1054 <p>Microsoft Internet Explorer (MSIE) will by default ignore
1055 server-generated error messages when they are "too small" and substitute
1056 its own "friendly" error messages. The size threshold varies depending on
1057 the type of error, but in general, if you make your error document
1058 greater than 512 bytes, then MSIE will show the server-generated
1059 error rather than masking it. More information is available in
1060 Microsoft Knowledge Base article <a href="http://support.microsoft.com/default.aspx?scid=kb;en-us;Q294807">Q294807</a>.</p>
1062 <p>Although most error messages can be overriden, there are certain
1063 circumstances where the internal messages are used regardless of the
1064 setting of <code class="directive"><a href="#errordocument">ErrorDocument</a></code>. In
1065 particular, if a malformed request is detected, normal request processing
1066 will be immediately halted and the internal error message returned.
1067 This is necessary to guard against security problems caused by
1070 <p>If you are using mod_proxy, you may wish to enable
1071 <code class="directive"><a href="../mod/mod_proxy.html#proxyerroroverride">ProxyErrorOverride</a></code> so that you can provide
1072 custom error messages on behalf of your Origin servers. If you don't enable ProxyErrorOverride,
1073 Apache will not generate custom error documents for proxied content.</p>
1077 <li><a href="../custom-error.html">documentation of
1078 customizable responses</a></li>
1081 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1082 <div class="directive-section"><h2><a name="ErrorLog" id="ErrorLog">ErrorLog</a> <a name="errorlog" id="errorlog">Directive</a></h2>
1083 <table class="directive">
1084 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location where the server will log errors</td></tr>
1085 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code> ErrorLog <var>file-path</var>|syslog[:<var>facility</var>]</code></td></tr>
1086 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ErrorLog logs/error_log (Unix) ErrorLog logs/error.log (Windows and OS/2)</code></td></tr>
1087 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
1088 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1089 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1091 <p>The <code class="directive">ErrorLog</code> directive sets the name of
1092 the file to which the server will log any errors it encounters. If
1093 the <var>file-path</var> is not absolute then it is assumed to be
1094 relative to the <code class="directive"><a href="#serverroot">ServerRoot</a></code>.</p>
1096 <div class="example"><h3>Example</h3><p><code>
1097 ErrorLog /var/log/httpd/error_log
1100 <p>If the <var>file-path</var>
1101 begins with a pipe (|) then it is assumed to be a command to spawn
1102 to handle the error log.</p>
1104 <div class="example"><h3>Example</h3><p><code>
1105 ErrorLog "|/usr/local/bin/httpd_errors"
1108 <p>Using <code>syslog</code> instead of a filename enables logging
1109 via syslogd(8) if the system supports it. The default is to use
1110 syslog facility <code>local7</code>, but you can override this by
1111 using the <code>syslog:<var>facility</var></code> syntax where
1112 <var>facility</var> can be one of the names usually documented in
1115 <div class="example"><h3>Example</h3><p><code>
1116 ErrorLog syslog:user
1119 <p>SECURITY: See the <a href="../misc/security_tips.html#serverroot">security tips</a>
1120 document for details on why your security could be compromised
1121 if the directory where log files are stored is writable by
1122 anyone other than the user that starts the server.</p>
1123 <div class="warning"><h3>Note</h3>
1124 <p>When entering a file path on non-Unix platforms, care should be taken
1125 to make sure that only forward slashed are used even though the platform
1126 may allow the use of back slashes. In general it is a good idea to always
1127 use forward slashes throughout the configuration files.</p>
1132 <li><code class="directive"><a href="#loglevel">LogLevel</a></code></li>
1133 <li><a href="../logs.html">Apache Log Files</a></li>
1136 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1137 <div class="directive-section"><h2><a name="FileETag" id="FileETag">FileETag</a> <a name="fileetag" id="fileetag">Directive</a></h2>
1138 <table class="directive">
1139 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File attributes used to create the ETag
1140 HTTP response header</td></tr>
1141 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>FileETag <var>component</var> ...</code></td></tr>
1142 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>FileETag INode MTime Size</code></td></tr>
1143 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
1144 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
1145 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1146 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1149 The <code class="directive">FileETag</code> directive configures the file
1150 attributes that are used to create the <code>ETag</code> (entity
1151 tag) response header field when the document is based on a file.
1152 (The <code>ETag</code> value is used in cache management to save
1153 network bandwidth.) In Apache 1.3.22 and earlier, the
1154 <code>ETag</code> value was <em>always</em> formed
1155 from the file's inode, size, and last-modified time (mtime). The
1156 <code class="directive">FileETag</code> directive allows you to choose
1157 which of these -- if any -- should be used. The recognized keywords are:
1161 <dt><strong>INode</strong></dt>
1162 <dd>The file's i-node number will be included in the calculation</dd>
1163 <dt><strong>MTime</strong></dt>
1164 <dd>The date and time the file was last modified will be included</dd>
1165 <dt><strong>Size</strong></dt>
1166 <dd>The number of bytes in the file will be included</dd>
1167 <dt><strong>All</strong></dt>
1168 <dd>All available fields will be used. This is equivalent to:
1169 <div class="example"><p><code>FileETag INode MTime Size</code></p></div></dd>
1170 <dt><strong>None</strong></dt>
1171 <dd>If a document is file-based, no <code>ETag</code> field will be
1172 included in the response</dd>
1175 <p>The <code>INode</code>, <code>MTime</code>, and <code>Size</code>
1176 keywords may be prefixed with either <code>+</code> or <code>-</code>,
1177 which allow changes to be made to the default setting inherited
1178 from a broader scope. Any keyword appearing without such a prefix
1179 immediately and completely cancels the inherited setting.</p>
1181 <p>If a directory's configuration includes
1182 <code>FileETag INode MTime Size</code>, and a
1183 subdirectory's includes <code>FileETag -INode</code>,
1184 the setting for that subdirectory (which will be inherited by
1185 any sub-subdirectories that don't override it) will be equivalent to
1186 <code>FileETag MTime Size</code>.</p>
1187 <div class="warning"><h3>Warning</h3>
1188 Do not change the default for directories or locations that have WebDAV
1189 enabled and use <code class="module"><a href="../mod/mod_dav_fs.html">mod_dav_fs</a></code> as a storage provider.
1190 <code class="module"><a href="../mod/mod_dav_fs.html">mod_dav_fs</a></code> uses <code>INode MTime Size</code>
1191 as a fixed format for <code>ETag</code> comparisons on conditional requests.
1192 These conditional requests will break if the <code>ETag</code> format is
1193 changed via <code class="directive">FileETag</code>.
1197 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1198 <div class="directive-section"><h2><a name="Files" id="Files"><Files></a> <a name="files" id="files">Directive</a></h2>
1199 <table class="directive">
1200 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Contains directives that apply to matched
1202 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><Files <var>filename</var>> ... </Files></code></td></tr>
1203 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
1204 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
1205 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1206 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1208 <p>The <code class="directive"><Files></code> directive
1209 limits the scope of the enclosed directives by filename. It is comparable
1210 to the <code class="directive"><a href="#directory"><Directory></a></code>
1211 and <code class="directive"><a href="#location"><Location></a></code>
1212 directives. It should be matched with a <code></Files></code>
1213 directive. The directives given within this section will be applied to
1214 any object with a basename (last component of filename) matching the
1215 specified filename. <code class="directive"><Files></code>
1216 sections are processed in the order they appear in the
1217 configuration file, after the <code class="directive"><a href="#directory"><Directory></a></code> sections and
1218 <code>.htaccess</code> files are read, but before <code class="directive"><a href="#location"><Location></a></code> sections. Note
1219 that <code class="directive"><Files></code> can be nested
1220 inside <code class="directive"><a href="#directory"><Directory></a></code> sections to restrict the
1221 portion of the filesystem they apply to.</p>
1223 <p>The <var>filename</var> argument should include a filename, or
1224 a wild-card string, where <code>?</code> matches any single character,
1225 and <code>*</code> matches any sequences of characters.
1226 <a class="glossarylink" href="../glossary.html#regex" title="see glossary">Regular expressions</a>
1227 can also be used, with the addition of the
1228 <code>~</code> character. For example:</p>
1230 <div class="example"><p><code>
1231 <Files ~ "\.(gif|jpe?g|png)$">
1234 <p>would match most common Internet graphics formats. <code class="directive"><a href="#filesmatch"><FilesMatch></a></code> is preferred,
1237 <p>Note that unlike <code class="directive"><a href="#directory"><Directory></a></code> and <code class="directive"><a href="#location"><Location></a></code> sections, <code class="directive"><Files></code> sections can be used inside
1238 <code>.htaccess</code> files. This allows users to control access to
1239 their own files, at a file-by-file level.</p>
1244 <li><a href="../sections.html">How <Directory>, <Location>
1245 and <Files> sections work</a> for an explanation of how these
1246 different sections are combined when a request is received</li>
1249 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1250 <div class="directive-section"><h2><a name="FilesMatch" id="FilesMatch"><FilesMatch></a> <a name="filesmatch" id="filesmatch">Directive</a></h2>
1251 <table class="directive">
1252 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Contains directives that apply to regular-expression matched
1254 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><FilesMatch <var>regex</var>> ... </FilesMatch></code></td></tr>
1255 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
1256 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
1257 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1258 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1260 <p>The <code class="directive"><FilesMatch></code> directive
1261 limits the scope of the enclosed directives by filename, just as the
1262 <code class="directive"><a href="#files"><Files></a></code> directive
1263 does. However, it accepts a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular
1264 expression</a>. For example:</p>
1266 <div class="example"><p><code>
1267 <FilesMatch "\.(gif|jpe?g|png)$">
1270 <p>would match most common Internet graphics formats.</p>
1274 <li><a href="../sections.html">How <Directory>, <Location>
1275 and <Files> sections work</a> for an explanation of how these
1276 different sections are combined when a request is received</li>
1279 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1280 <div class="directive-section"><h2><a name="ForceType" id="ForceType">ForceType</a> <a name="forcetype" id="forcetype">Directive</a></h2>
1281 <table class="directive">
1282 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Forces all matching files to be served with the specified
1283 media type in the HTTP Content-Type header field</td></tr>
1284 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ForceType <var>media-type</var>|None</code></td></tr>
1285 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
1286 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
1287 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1288 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1289 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Moved to the core in Apache 2.0</td></tr>
1291 <p>When placed into an <code>.htaccess</code> file or a
1292 <code class="directive"><a href="#directory"><Directory></a></code>, or
1293 <code class="directive"><a href="#location"><Location></a></code> or
1294 <code class="directive"><a href="#files"><Files></a></code>
1295 section, this directive forces all matching files to be served
1296 with the content type identification given by
1297 <var>media-type</var>. For example, if you had a directory full of
1298 GIF files, but did not want to label them all with <code>.gif</code>,
1299 you might want to use:</p>
1301 <div class="example"><p><code>
1305 <p>Note that this directive overrides other indirect media type
1306 associations defined in mime.types or via the
1307 <code class="directive"><a href="../mod/mod_mime.html#addtype">AddType</a></code>.</p>
1309 <p>You can also override more general
1310 <code class="directive">ForceType</code> settings
1311 by using the value of <code>None</code>:</p>
1313 <div class="example"><p><code>
1314 # force all files to be image/gif:<br />
1315 <Location /images><br />
1316 <span class="indent">
1317 ForceType image/gif<br />
1319 </Location><br />
1321 # but normal mime-type associations here:<br />
1322 <Location /images/mixed><br />
1323 <span class="indent">
1324 ForceType None<br />
1330 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1331 <div class="directive-section"><h2><a name="HostnameLookups" id="HostnameLookups">HostnameLookups</a> <a name="hostnamelookups" id="hostnamelookups">Directive</a></h2>
1332 <table class="directive">
1333 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables DNS lookups on client IP addresses</td></tr>
1334 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>HostnameLookups On|Off|Double</code></td></tr>
1335 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>HostnameLookups Off</code></td></tr>
1336 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
1337 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1338 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1340 <p>This directive enables DNS lookups so that host names can be
1341 logged (and passed to CGIs/SSIs in <code>REMOTE_HOST</code>).
1342 The value <code>Double</code> refers to doing double-reverse
1343 DNS lookup. That is, after a reverse lookup is performed, a forward
1344 lookup is then performed on that result. At least one of the IP
1345 addresses in the forward lookup must match the original
1346 address. (In "tcpwrappers" terminology this is called
1347 <code>PARANOID</code>.)</p>
1349 <p>Regardless of the setting, when <code class="module"><a href="../mod/mod_authz_host.html">mod_authz_host</a></code> is
1350 used for controlling access by hostname, a double reverse lookup
1351 will be performed. This is necessary for security. Note that the
1352 result of this double-reverse isn't generally available unless you
1353 set <code>HostnameLookups Double</code>. For example, if only
1354 <code>HostnameLookups On</code> and a request is made to an object
1355 that is protected by hostname restrictions, regardless of whether
1356 the double-reverse fails or not, CGIs will still be passed the
1357 single-reverse result in <code>REMOTE_HOST</code>.</p>
1359 <p>The default is <code>Off</code> in order to save the network
1360 traffic for those sites that don't truly need the reverse
1361 lookups done. It is also better for the end users because they
1362 don't have to suffer the extra latency that a lookup entails.
1363 Heavily loaded sites should leave this directive
1364 <code>Off</code>, since DNS lookups can take considerable
1365 amounts of time. The utility <code class="program"><a href="../programs/logresolve.html">logresolve</a></code>, compiled by
1366 default to the <code>bin</code> subdirectory of your installation
1367 directory, can be used to look up host names from logged IP addresses
1371 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1372 <div class="directive-section"><h2><a name="If" id="If"><If></a> <a name="if" id="if">Directive</a></h2>
1373 <table class="directive">
1374 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Contains directives that apply only if a condition is
1375 satisfied by a request at runtime</td></tr>
1376 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><If <var>expression</var>> ... </If></code></td></tr>
1377 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
1378 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
1379 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1380 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1382 <p>The <code class="directive"><If></code> directive
1383 evaluates an expression at runtime, and applies the enclosed
1384 directives if and only if the expression evaluates to true.
1387 <div class="example"><p><code>
1388 <If "$req{Host} = ''">
1391 <p>would match HTTP/1.0 requests without a <var>Host:</var> header.</p>
1393 <p>You may compare the value of any variable in the request headers
1394 ($req), response headers ($resp) or environment ($env) in your
1399 <li><a href="../sections.html">How <Directory>, <Location>,
1400 <Files> sections work</a> for an explanation of how these
1401 different sections are combined when a request is received.
1402 <code class="directive"><If></code> has the same precedence
1403 and usage as <code class="directive"><Files></code></li>
1406 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1407 <div class="directive-section"><h2><a name="IfDefine" id="IfDefine"><IfDefine></a> <a name="ifdefine" id="ifdefine">Directive</a></h2>
1408 <table class="directive">
1409 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Encloses directives that will be processed only
1410 if a test is true at startup</td></tr>
1411 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><IfDefine [!]<var>parameter-name</var>> ...
1412 </IfDefine></code></td></tr>
1413 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
1414 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
1415 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1416 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1418 <p>The <code><IfDefine <var>test</var>>...</IfDefine>
1419 </code> section is used to mark directives that are conditional. The
1420 directives within an <code class="directive"><IfDefine></code>
1421 section are only processed if the <var>test</var> is true. If <var>
1422 test</var> is false, everything between the start and end markers is
1425 <p>The <var>test</var> in the <code class="directive"><IfDefine></code> section directive can be one of two forms:</p>
1428 <li><var>parameter-name</var></li>
1430 <li><code>!</code><var>parameter-name</var></li>
1433 <p>In the former case, the directives between the start and end
1434 markers are only processed if the parameter named
1435 <var>parameter-name</var> is defined. The second format reverses
1436 the test, and only processes the directives if
1437 <var>parameter-name</var> is <strong>not</strong> defined.</p>
1439 <p>The <var>parameter-name</var> argument is a define as given on the
1440 <code class="program"><a href="../programs/httpd.html">httpd</a></code> command line via <code>-D<var>parameter</var>
1441 </code> at the time the server was started or by the <code class="directive"><a href="#define">Define</a></code> directive.</p>
1443 <p><code class="directive"><IfDefine></code> sections are
1444 nest-able, which can be used to implement simple
1445 multiple-parameter tests. Example:</p>
1447 <div class="example"><p><code>
1448 httpd -DReverseProxy -DUseCache -DMemCache ...<br />
1451 <IfDefine ReverseProxy><br />
1452 <span class="indent">
1453 LoadModule proxy_module modules/mod_proxy.so<br />
1454 LoadModule proxy_http_module modules/mod_proxy_http.so<br />
1455 <IfDefine UseCache><br />
1456 <span class="indent">
1457 LoadModule cache_module modules/mod_cache.so<br />
1458 <IfDefine MemCache><br />
1459 <span class="indent">
1460 LoadModule mem_cache_module modules/mod_mem_cache.so<br />
1462 </IfDefine><br />
1463 <IfDefine !MemCache><br />
1464 <span class="indent">
1465 LoadModule disk_cache_module modules/mod_disk_cache.so<br />
1475 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1476 <div class="directive-section"><h2><a name="IfModule" id="IfModule"><IfModule></a> <a name="ifmodule" id="ifmodule">Directive</a></h2>
1477 <table class="directive">
1478 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Encloses directives that are processed conditional on the
1479 presence or absence of a specific module</td></tr>
1480 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><IfModule [!]<var>module-file</var>|<var>module-identifier</var>> ...
1481 </IfModule></code></td></tr>
1482 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
1483 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
1484 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1485 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1486 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Module identifiers are available in version 2.1 and
1489 <p>The <code><IfModule <var>test</var>>...</IfModule></code>
1490 section is used to mark directives that are conditional on the presence of
1491 a specific module. The directives within an <code class="directive"><IfModule></code> section are only processed if the <var>test</var>
1492 is true. If <var>test</var> is false, everything between the start and
1493 end markers is ignored.</p>
1495 <p>The <var>test</var> in the <code class="directive"><IfModule></code> section directive can be one of two forms:</p>
1498 <li><var>module</var></li>
1500 <li>!<var>module</var></li>
1503 <p>In the former case, the directives between the start and end
1504 markers are only processed if the module named <var>module</var>
1505 is included in Apache -- either compiled in or
1506 dynamically loaded using <code class="directive"><a href="../mod/mod_so.html#loadmodule">LoadModule</a></code>. The second format reverses the test,
1507 and only processes the directives if <var>module</var> is
1508 <strong>not</strong> included.</p>
1510 <p>The <var>module</var> argument can be either the module identifier or
1511 the file name of the module, at the time it was compiled. For example,
1512 <code>rewrite_module</code> is the identifier and
1513 <code>mod_rewrite.c</code> is the file name. If a module consists of
1514 several source files, use the name of the file containing the string
1515 <code>STANDARD20_MODULE_STUFF</code>.</p>
1517 <p><code class="directive"><IfModule></code> sections are
1518 nest-able, which can be used to implement simple multiple-module
1521 <div class="note">This section should only be used if you need to have one
1522 configuration file that works whether or not a specific module
1523 is available. In normal operation, directives need not be
1524 placed in <code class="directive"><IfModule></code>
1528 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1529 <div class="directive-section"><h2><a name="Include" id="Include">Include</a> <a name="include" id="include">Directive</a></h2>
1530 <table class="directive">
1531 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Includes other configuration files from within
1532 the server configuration files</td></tr>
1533 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Include <var>file-path</var>|<var>directory-path</var></code></td></tr>
1534 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
1535 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1536 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1537 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Wildcard matching available in 2.0.41 and later</td></tr>
1539 <p>This directive allows inclusion of other configuration files
1540 from within the server configuration files.</p>
1542 <p>Shell-style (<code>fnmatch()</code>) wildcard characters can be used to
1543 include several files at once, in alphabetical order. In
1544 addition, if <code class="directive">Include</code> points to a directory,
1545 rather than a file, Apache will read all files in that directory
1546 and any subdirectory. However, including entire directories is not
1547 recommended, because it is easy to accidentally leave temporary
1548 files in a directory that can cause <code class="program"><a href="../programs/httpd.html">httpd</a></code> to
1549 fail. Instead, we encourage you to use the wildcard syntax shown
1550 below, to include files that match a particular pattern, such as
1551 *.conf, for example.</p>
1553 <p>The file path specified may be an absolute path, or may be relative
1554 to the <code class="directive"><a href="#serverroot">ServerRoot</a></code> directory.</p>
1558 <div class="example"><p><code>
1559 Include /usr/local/apache2/conf/ssl.conf<br />
1560 Include /usr/local/apache2/conf/vhosts/*.conf
1563 <p>Or, providing paths relative to your <code class="directive"><a href="#serverroot">ServerRoot</a></code> directory:</p>
1565 <div class="example"><p><code>
1566 Include conf/ssl.conf<br />
1567 Include conf/vhosts/*.conf
1572 <li><code class="program"><a href="../programs/apachectl.html">apachectl</a></code></li>
1575 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1576 <div class="directive-section"><h2><a name="KeepAlive" id="KeepAlive">KeepAlive</a> <a name="keepalive" id="keepalive">Directive</a></h2>
1577 <table class="directive">
1578 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables HTTP persistent connections</td></tr>
1579 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>KeepAlive On|Off</code></td></tr>
1580 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>KeepAlive On</code></td></tr>
1581 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
1582 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1583 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1585 <p>The Keep-Alive extension to HTTP/1.0 and the persistent
1586 connection feature of HTTP/1.1 provide long-lived HTTP sessions
1587 which allow multiple requests to be sent over the same TCP
1588 connection. In some cases this has been shown to result in an
1589 almost 50% speedup in latency times for HTML documents with
1590 many images. To enable Keep-Alive connections, set
1591 <code>KeepAlive On</code>.</p>
1593 <p>For HTTP/1.0 clients, Keep-Alive connections will only be
1594 used if they are specifically requested by a client. In
1595 addition, a Keep-Alive connection with an HTTP/1.0 client can
1596 only be used when the length of the content is known in
1597 advance. This implies that dynamic content such as CGI output,
1598 SSI pages, and server-generated directory listings will
1599 generally not use Keep-Alive connections to HTTP/1.0 clients.
1600 For HTTP/1.1 clients, persistent connections are the default
1601 unless otherwise specified. If the client requests it, chunked
1602 encoding will be used in order to send content of unknown
1603 length over persistent connections.</p>
1605 <p>When a client uses a Keep-Alive connection it will be counted
1606 as a single "request" for the <code class="directive"><a href="../mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code> directive, regardless
1607 of how many requests are sent using the connection.</p>
1611 <li><code class="directive"><a href="#maxkeepaliverequests">MaxKeepAliveRequests</a></code></li>
1614 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1615 <div class="directive-section"><h2><a name="KeepAliveTimeout" id="KeepAliveTimeout">KeepAliveTimeout</a> <a name="keepalivetimeout" id="keepalivetimeout">Directive</a></h2>
1616 <table class="directive">
1617 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Amount of time the server will wait for subsequent
1618 requests on a persistent connection</td></tr>
1619 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>KeepAliveTimeout <var>num</var>[ms]</code></td></tr>
1620 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>KeepAliveTimeout 5</code></td></tr>
1621 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
1622 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1623 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1624 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Specifying a value in milliseconds is available in
1625 Apache 2.3.2 and later</td></tr>
1627 <p>The number of seconds Apache will wait for a subsequent
1628 request before closing the connection. By adding a postfix of ms the
1629 timeout can be also set in milliseconds. Once a request has been
1630 received, the timeout value specified by the
1631 <code class="directive"><a href="#timeout">Timeout</a></code> directive applies.</p>
1633 <p>Setting <code class="directive">KeepAliveTimeout</code> to a high value
1634 may cause performance problems in heavily loaded servers. The
1635 higher the timeout, the more server processes will be kept
1636 occupied waiting on connections with idle clients.</p>
1638 <p>In a name-based virtual host context, the value of the first
1639 defined virtual host (the default host) in a set of <code class="directive"><a href="#namevirtualhost">NameVirtualHost</a></code> will be used.
1640 The other values will be ignored.</p>
1643 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1644 <div class="directive-section"><h2><a name="Limit" id="Limit"><Limit></a> <a name="limit" id="limit">Directive</a></h2>
1645 <table class="directive">
1646 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Restrict enclosed access controls to only certain HTTP
1648 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><Limit <var>method</var> [<var>method</var>] ... > ...
1649 </Limit></code></td></tr>
1650 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
1651 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig, Limit</td></tr>
1652 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1653 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1655 <p>Access controls are normally effective for
1656 <strong>all</strong> access methods, and this is the usual
1657 desired behavior. <strong>In the general case, access control
1658 directives should not be placed within a
1659 <code class="directive"><Limit></code> section.</strong></p>
1661 <p>The purpose of the <code class="directive"><Limit></code>
1662 directive is to restrict the effect of the access controls to the
1663 nominated HTTP methods. For all other methods, the access
1664 restrictions that are enclosed in the <code class="directive"><Limit></code> bracket <strong>will have no
1665 effect</strong>. The following example applies the access control
1666 only to the methods <code>POST</code>, <code>PUT</code>, and
1667 <code>DELETE</code>, leaving all other methods unprotected:</p>
1669 <div class="example"><p><code>
1670 <Limit POST PUT DELETE><br />
1671 <span class="indent">
1672 Require valid-user<br />
1677 <p>The method names listed can be one or more of: <code>GET</code>,
1678 <code>POST</code>, <code>PUT</code>, <code>DELETE</code>,
1679 <code>CONNECT</code>, <code>OPTIONS</code>,
1680 <code>PATCH</code>, <code>PROPFIND</code>, <code>PROPPATCH</code>,
1681 <code>MKCOL</code>, <code>COPY</code>, <code>MOVE</code>,
1682 <code>LOCK</code>, and <code>UNLOCK</code>. <strong>The method name is
1683 case-sensitive.</strong> If <code>GET</code> is used it will also
1684 restrict <code>HEAD</code> requests. The <code>TRACE</code> method
1685 cannot be limited (see <code class="directive"><a href="#traceenable">TraceEnable</a></code>).</p>
1687 <div class="warning">A <code class="directive"><a href="#limitexcept"><LimitExcept></a></code> section should always be
1688 used in preference to a <code class="directive"><Limit></code>
1689 section when restricting access, since a <code class="directive"><a href="#limitexcept"><LimitExcept></a></code> section provides protection
1690 against arbitrary methods.</div>
1692 <p>The <code class="directive"><Limit></code> and
1693 <code class="directive"><a href="#limitexcept"><LimitExcept></a></code>
1694 directives may be nested. In this case, each successive level of
1695 <code class="directive"><Limit></code> or <code class="directive"><a href="#limitexcept"><LimitExcept></a></code> directives must
1696 further restrict the set of methods to which access controls apply.</p>
1698 <div class="warning">When using
1699 <code class="directive"><Limit></code> or
1700 <code class="directive"><LimitExcept></code> directives with
1701 the <code class="directive"><a href="../mod/mod_authz_core.html#require">Require</a></code> directive,
1702 note that the first <code class="directive"><a href="../mod/mod_authz_core.html#require">Require</a></code>
1703 to succeed authorizes the request, regardless of the presence of other
1704 <code class="directive"><a href="../mod/mod_authz_core.html#require">Require</a></code> directives.</div>
1706 <p>For example, given the following configuration, all users will
1707 be authorized for <code>POST</code> requests, and the
1708 <code>Require group editors</code> directive will be ignored
1711 <div class="example"><p><code>
1712 <LimitExcept GET>
1713 <span class="indent">
1716 </LimitExcept><br />
1718 <span class="indent">
1719 Require group editors
1725 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1726 <div class="directive-section"><h2><a name="LimitExcept" id="LimitExcept"><LimitExcept></a> <a name="limitexcept" id="limitexcept">Directive</a></h2>
1727 <table class="directive">
1728 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Restrict access controls to all HTTP methods
1729 except the named ones</td></tr>
1730 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><LimitExcept <var>method</var> [<var>method</var>] ... > ...
1731 </LimitExcept></code></td></tr>
1732 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
1733 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig, Limit</td></tr>
1734 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1735 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1737 <p><code class="directive"><LimitExcept></code> and
1738 <code></LimitExcept></code> are used to enclose
1739 a group of access control directives which will then apply to any
1740 HTTP access method <strong>not</strong> listed in the arguments;
1741 i.e., it is the opposite of a <code class="directive"><a href="#limit"><Limit></a></code> section and can be used to control
1742 both standard and nonstandard/unrecognized methods. See the
1743 documentation for <code class="directive"><a href="#limit"><Limit></a></code> for more details.</p>
1747 <div class="example"><p><code>
1748 <LimitExcept POST GET><br />
1749 <span class="indent">
1750 Require valid-user<br />
1752 </LimitExcept>
1757 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1758 <div class="directive-section"><h2><a name="LimitInternalRecursion" id="LimitInternalRecursion">LimitInternalRecursion</a> <a name="limitinternalrecursion" id="limitinternalrecursion">Directive</a></h2>
1759 <table class="directive">
1760 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determine maximum number of internal redirects and nested
1761 subrequests</td></tr>
1762 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitInternalRecursion <var>number</var> [<var>number</var>]</code></td></tr>
1763 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitInternalRecursion 10</code></td></tr>
1764 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
1765 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1766 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1767 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.0.47 and later</td></tr>
1769 <p>An internal redirect happens, for example, when using the <code class="directive"><a href="../mod/mod_actions.html#action">Action</a></code> directive, which internally
1770 redirects the original request to a CGI script. A subrequest is Apache's
1771 mechanism to find out what would happen for some URI if it were requested.
1772 For example, <code class="module"><a href="../mod/mod_dir.html">mod_dir</a></code> uses subrequests to look for the
1773 files listed in the <code class="directive"><a href="../mod/mod_dir.html#directoryindex">DirectoryIndex</a></code>
1776 <p><code class="directive">LimitInternalRecursion</code> prevents the server
1777 from crashing when entering an infinite loop of internal redirects or
1778 subrequests. Such loops are usually caused by misconfigurations.</p>
1780 <p>The directive stores two different limits, which are evaluated on
1781 per-request basis. The first <var>number</var> is the maximum number of
1782 internal redirects, that may follow each other. The second <var>number</var>
1783 determines, how deep subrequests may be nested. If you specify only one
1784 <var>number</var>, it will be assigned to both limits.</p>
1786 <div class="example"><h3>Example</h3><p><code>
1787 LimitInternalRecursion 5
1791 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1792 <div class="directive-section"><h2><a name="LimitRequestBody" id="LimitRequestBody">LimitRequestBody</a> <a name="limitrequestbody" id="limitrequestbody">Directive</a></h2>
1793 <table class="directive">
1794 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Restricts the total size of the HTTP request body sent
1795 from the client</td></tr>
1796 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitRequestBody <var>bytes</var></code></td></tr>
1797 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitRequestBody 0</code></td></tr>
1798 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
1799 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
1800 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1801 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1803 <p>This directive specifies the number of <var>bytes</var> from 0
1804 (meaning unlimited) to 2147483647 (2GB) that are allowed in a
1807 <p>The <code class="directive">LimitRequestBody</code> directive allows
1808 the user to set a limit on the allowed size of an HTTP request
1809 message body within the context in which the directive is given
1810 (server, per-directory, per-file or per-location). If the client
1811 request exceeds that limit, the server will return an error
1812 response instead of servicing the request. The size of a normal
1813 request message body will vary greatly depending on the nature of
1814 the resource and the methods allowed on that resource. CGI scripts
1815 typically use the message body for retrieving form information.
1816 Implementations of the <code>PUT</code> method will require
1817 a value at least as large as any representation that the server
1818 wishes to accept for that resource.</p>
1820 <p>This directive gives the server administrator greater
1821 control over abnormal client request behavior, which may be
1822 useful for avoiding some forms of denial-of-service
1825 <p>If, for example, you are permitting file upload to a particular
1826 location, and wish to limit the size of the uploaded file to 100K,
1827 you might use the following directive:</p>
1829 <div class="example"><p><code>
1830 LimitRequestBody 102400
1835 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1836 <div class="directive-section"><h2><a name="LimitRequestFields" id="LimitRequestFields">LimitRequestFields</a> <a name="limitrequestfields" id="limitrequestfields">Directive</a></h2>
1837 <table class="directive">
1838 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the number of HTTP request header fields that
1839 will be accepted from the client</td></tr>
1840 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitRequestFields <var>number</var></code></td></tr>
1841 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitRequestFields 100</code></td></tr>
1842 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
1843 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1844 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1846 <p><var>Number</var> is an integer from 0 (meaning unlimited) to
1847 32767. The default value is defined by the compile-time
1848 constant <code>DEFAULT_LIMIT_REQUEST_FIELDS</code> (100 as
1851 <p>The <code class="directive">LimitRequestFields</code> directive allows
1852 the server administrator to modify the limit on the number of
1853 request header fields allowed in an HTTP request. A server needs
1854 this value to be larger than the number of fields that a normal
1855 client request might include. The number of request header fields
1856 used by a client rarely exceeds 20, but this may vary among
1857 different client implementations, often depending upon the extent
1858 to which a user has configured their browser to support detailed
1859 content negotiation. Optional HTTP extensions are often expressed
1860 using request header fields.</p>
1862 <p>This directive gives the server administrator greater
1863 control over abnormal client request behavior, which may be
1864 useful for avoiding some forms of denial-of-service attacks.
1865 The value should be increased if normal clients see an error
1866 response from the server that indicates too many fields were
1867 sent in the request.</p>
1871 <div class="example"><p><code>
1872 LimitRequestFields 50
1877 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1878 <div class="directive-section"><h2><a name="LimitRequestFieldSize" id="LimitRequestFieldSize">LimitRequestFieldSize</a> <a name="limitrequestfieldsize" id="limitrequestfieldsize">Directive</a></h2>
1879 <table class="directive">
1880 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the size of the HTTP request header allowed from the
1882 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitRequestFieldSize <var>bytes</var></code></td></tr>
1883 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitRequestFieldSize 8190</code></td></tr>
1884 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
1885 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1886 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1888 <p>This directive specifies the number of <var>bytes</var>
1889 that will be allowed in an HTTP request header.</p>
1891 <p>The <code class="directive">LimitRequestFieldSize</code> directive
1892 allows the server administrator to reduce or increase the limit
1893 on the allowed size of an HTTP request header field. A server
1894 needs this value to be large enough to hold any one header field
1895 from a normal client request. The size of a normal request header
1896 field will vary greatly among different client implementations,
1897 often depending upon the extent to which a user has configured
1898 their browser to support detailed content negotiation. SPNEGO
1899 authentication headers can be up to 12392 bytes.</p>
1901 <p>This directive gives the server administrator greater
1902 control over abnormal client request behavior, which may be
1903 useful for avoiding some forms of denial-of-service attacks.</p>
1907 <div class="example"><p><code>
1908 LimitRequestFieldSize 4094
1911 <div class="note">Under normal conditions, the value should not be changed from
1916 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1917 <div class="directive-section"><h2><a name="LimitRequestLine" id="LimitRequestLine">LimitRequestLine</a> <a name="limitrequestline" id="limitrequestline">Directive</a></h2>
1918 <table class="directive">
1919 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit the size of the HTTP request line that will be accepted
1920 from the client</td></tr>
1921 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitRequestLine <var>bytes</var></code></td></tr>
1922 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitRequestLine 8190</code></td></tr>
1923 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
1924 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1925 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1927 <p>This directive sets the number of <var>bytes</var> that will be
1928 allowed on the HTTP request-line.</p>
1930 <p>The <code class="directive">LimitRequestLine</code> directive allows
1931 the server administrator to reduce or increase the limit on the allowed size
1932 of a client's HTTP request-line. Since the request-line consists of the
1933 HTTP method, URI, and protocol version, the
1934 <code class="directive">LimitRequestLine</code> directive places a
1935 restriction on the length of a request-URI allowed for a request
1936 on the server. A server needs this value to be large enough to
1937 hold any of its resource names, including any information that
1938 might be passed in the query part of a <code>GET</code> request.</p>
1940 <p>This directive gives the server administrator greater
1941 control over abnormal client request behavior, which may be
1942 useful for avoiding some forms of denial-of-service attacks.</p>
1946 <div class="example"><p><code>
1947 LimitRequestLine 4094
1950 <div class="note">Under normal conditions, the value should not be changed from
1954 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1955 <div class="directive-section"><h2><a name="LimitXMLRequestBody" id="LimitXMLRequestBody">LimitXMLRequestBody</a> <a name="limitxmlrequestbody" id="limitxmlrequestbody">Directive</a></h2>
1956 <table class="directive">
1957 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the size of an XML-based request body</td></tr>
1958 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitXMLRequestBody <var>bytes</var></code></td></tr>
1959 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitXMLRequestBody 1000000</code></td></tr>
1960 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
1961 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
1962 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1963 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1965 <p>Limit (in bytes) on maximum size of an XML-based request
1966 body. A value of <code>0</code> will disable any checking.</p>
1970 <div class="example"><p><code>
1971 LimitXMLRequestBody 0
1976 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
1977 <div class="directive-section"><h2><a name="Location" id="Location"><Location></a> <a name="location" id="location">Directive</a></h2>
1978 <table class="directive">
1979 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Applies the enclosed directives only to matching
1981 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><Location
1982 <var>URL-path</var>|<var>URL</var>> ... </Location></code></td></tr>
1983 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
1984 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
1985 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
1987 <p>The <code class="directive"><Location></code> directive
1988 limits the scope of the enclosed directives by URL. It is similar to the
1989 <code class="directive"><a href="#directory"><Directory></a></code>
1990 directive, and starts a subsection which is terminated with a
1991 <code></Location></code> directive. <code class="directive"><Location></code> sections are processed in the
1992 order they appear in the configuration file, after the <code class="directive"><a href="#directory"><Directory></a></code> sections and
1993 <code>.htaccess</code> files are read, and after the <code class="directive"><a href="#files"><Files></a></code> sections.</p>
1995 <p><code class="directive"><Location></code> sections operate
1996 completely outside the filesystem. This has several consequences.
1997 Most importantly, <code class="directive"><Location></code>
1998 directives should not be used to control access to filesystem
1999 locations. Since several different URLs may map to the same
2000 filesystem location, such access controls may by circumvented.</p>
2002 <div class="note"><h3>When to use <code class="directive"><Location></code></h3>
2004 <p>Use <code class="directive"><Location></code> to apply
2005 directives to content that lives outside the filesystem. For
2006 content that lives in the filesystem, use <code class="directive"><a href="#directory"><Directory></a></code> and <code class="directive"><a href="#files"><Files></a></code>. An exception is
2007 <code><Location /></code>, which is an easy way to
2008 apply a configuration to the entire server.</p>
2011 <p>For all origin (non-proxy) requests, the URL to be matched is a
2012 URL-path of the form <code>/path/</code>. <em>No scheme, hostname,
2013 port, or query string may be included.</em> For proxy requests, the
2014 URL to be matched is of the form
2015 <code>scheme://servername/path</code>, and you must include the
2018 <p>The URL may use wildcards. In a wild-card string, <code>?</code> matches
2019 any single character, and <code>*</code> matches any sequences of
2020 characters. Neither wildcard character matches a / in the URL-path.</p>
2022 <p><a class="glossarylink" href="../glossary.html#regex" title="see glossary">Regular expressions</a>
2023 can also be used, with the addition of the <code>~</code>
2024 character. For example:</p>
2026 <div class="example"><p><code>
2027 <Location ~ "/(extra|special)/data">
2030 <p>would match URLs that contained the substring <code>/extra/data</code>
2031 or <code>/special/data</code>. The directive <code class="directive"><a href="#locationmatch"><LocationMatch></a></code> behaves
2032 identical to the regex version of <code class="directive"><Location></code>, and is preferred, for the
2033 simple reason that <code>~</code> is hard to distinguish from
2034 <code>-</code> in many fonts.</p>
2036 <p>The <code class="directive"><Location></code>
2037 functionality is especially useful when combined with the
2038 <code class="directive"><a href="#sethandler">SetHandler</a></code>
2039 directive. For example, to enable status requests, but allow them
2040 only from browsers at <code>example.com</code>, you might use:</p>
2042 <div class="example"><p><code>
2043 <Location /status><br />
2044 <span class="indent">
2045 SetHandler server-status<br />
2046 Order Deny,Allow<br />
2048 Allow from .example.com<br />
2053 <div class="note"><h3>Note about / (slash)</h3>
2054 <p>The slash character has special meaning depending on where in a
2055 URL it appears. People may be used to its behavior in the filesystem
2056 where multiple adjacent slashes are frequently collapsed to a single
2057 slash (<em>i.e.</em>, <code>/home///foo</code> is the same as
2058 <code>/home/foo</code>). In URL-space this is not necessarily true.
2059 The <code class="directive"><a href="#locationmatch"><LocationMatch></a></code>
2060 directive and the regex version of <code class="directive"><Location></code> require you to explicitly specify multiple
2061 slashes if that is your intention.</p>
2063 <p>For example, <code><LocationMatch ^/abc></code> would match
2064 the request URL <code>/abc</code> but not the request URL <code>
2065 //abc</code>. The (non-regex) <code class="directive"><Location></code> directive behaves similarly when used for
2066 proxy requests. But when (non-regex) <code class="directive"><Location></code> is used for non-proxy requests it will
2067 implicitly match multiple slashes with a single slash. For example,
2068 if you specify <code><Location /abc/def></code> and the
2069 request is to <code>/abc//def</code> then it will match.</p>
2074 <li><a href="../sections.html">How <Directory>, <Location>
2075 and <Files> sections work</a> for an explanation of how these
2076 different sections are combined when a request is received.</li>
2077 <li><code class="directive"><a href="#locationmatch">LocationMatch</a></code></li>
2080 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2081 <div class="directive-section"><h2><a name="LocationMatch" id="LocationMatch"><LocationMatch></a> <a name="locationmatch" id="locationmatch">Directive</a></h2>
2082 <table class="directive">
2083 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Applies the enclosed directives only to regular-expression
2084 matching URLs</td></tr>
2085 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><LocationMatch
2086 <var>regex</var>> ... </LocationMatch></code></td></tr>
2087 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
2088 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2089 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2091 <p>The <code class="directive"><LocationMatch></code> directive
2092 limits the scope of the enclosed directives by URL, in an identical manner
2093 to <code class="directive"><a href="#location"><Location></a></code>. However,
2094 it takes a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>
2095 as an argument instead of a simple string. For example:</p>
2097 <div class="example"><p><code>
2098 <LocationMatch "/(extra|special)/data">
2101 <p>would match URLs that contained the substring <code>/extra/data</code>
2102 or <code>/special/data</code>.</p>
2106 <li><a href="../sections.html">How <Directory>, <Location>
2107 and <Files> sections work</a> for an explanation of how these
2108 different sections are combined when a request is received</li>
2111 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2112 <div class="directive-section"><h2><a name="LogLevel" id="LogLevel">LogLevel</a> <a name="loglevel" id="loglevel">Directive</a></h2>
2113 <table class="directive">
2114 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Controls the verbosity of the ErrorLog</td></tr>
2115 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LogLevel <var>level</var></code></td></tr>
2116 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LogLevel warn</code></td></tr>
2117 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
2118 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2119 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2121 <p><code class="directive">LogLevel</code> adjusts the verbosity of the
2122 messages recorded in the error logs (see <code class="directive"><a href="#errorlog">ErrorLog</a></code> directive). The following
2123 <var>level</var>s are available, in order of decreasing
2126 <table class="bordered">
2129 <th><strong>Level</strong> </th>
2131 <th><strong>Description</strong> </th>
2133 <th><strong>Example</strong> </th>
2137 <td><code>emerg</code> </td>
2139 <td>Emergencies - system is unusable.</td>
2141 <td>"Child cannot open lock file. Exiting"</td>
2145 <td><code>alert</code> </td>
2147 <td>Action must be taken immediately.</td>
2149 <td>"getpwuid: couldn't determine user name from uid"</td>
2153 <td><code>crit</code> </td>
2155 <td>Critical Conditions.</td>
2157 <td>"socket: Failed to get a socket, exiting child"</td>
2161 <td><code>error</code> </td>
2163 <td>Error conditions.</td>
2165 <td>"Premature end of script headers"</td>
2169 <td><code>warn</code> </td>
2171 <td>Warning conditions.</td>
2173 <td>"child process 1234 did not exit, sending another
2178 <td><code>notice</code> </td>
2180 <td>Normal but significant condition.</td>
2182 <td>"httpd: caught SIGBUS, attempting to dump core in
2187 <td><code>info</code> </td>
2189 <td>Informational.</td>
2191 <td>"Server seems busy, (you may need to increase
2192 StartServers, or Min/MaxSpareServers)..."</td>
2196 <td><code>debug</code> </td>
2198 <td>Debug-level messages</td>
2200 <td>"Opening config file ..."</td>
2204 <p>When a particular level is specified, messages from all
2205 other levels of higher significance will be reported as well.
2206 <em>E.g.</em>, when <code>LogLevel info</code> is specified,
2207 then messages with log levels of <code>notice</code> and
2208 <code>warn</code> will also be posted.</p>
2210 <p>Using a level of at least <code>crit</code> is
2215 <div class="example"><p><code>
2219 <div class="note"><h3>Note</h3>
2220 <p>When logging to a regular file messages of the level
2221 <code>notice</code> cannot be suppressed and thus are always
2222 logged. However, this doesn't apply when logging is done
2223 using <code>syslog</code>.</p>
2227 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2228 <div class="directive-section"><h2><a name="MaxKeepAliveRequests" id="MaxKeepAliveRequests">MaxKeepAliveRequests</a> <a name="maxkeepaliverequests" id="maxkeepaliverequests">Directive</a></h2>
2229 <table class="directive">
2230 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of requests allowed on a persistent
2231 connection</td></tr>
2232 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxKeepAliveRequests <var>number</var></code></td></tr>
2233 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxKeepAliveRequests 100</code></td></tr>
2234 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
2235 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2236 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2238 <p>The <code class="directive">MaxKeepAliveRequests</code> directive
2239 limits the number of requests allowed per connection when
2240 <code class="directive"><a href="#keepalive">KeepAlive</a></code> is on. If it is
2241 set to <code>0</code>, unlimited requests will be allowed. We
2242 recommend that this setting be kept to a high value for maximum
2243 server performance.</p>
2247 <div class="example"><p><code>
2248 MaxKeepAliveRequests 500
2252 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2253 <div class="directive-section"><h2><a name="Mutex" id="Mutex">Mutex</a> <a name="mutex" id="mutex">Directive</a></h2>
2254 <table class="directive">
2255 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures mutex mechanism and lock file directory for all
2256 or specified mutexes</td></tr>
2257 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Mutex <var>mechanism</var> [default|<var>mutex-name</var>] ... [OmitPID]</code></td></tr>
2258 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Mutex default</code></td></tr>
2259 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
2260 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2261 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2262 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.3.4 and later</td></tr>
2264 <p>The <code class="directive">Mutex</code> directive sets the mechanism,
2265 and optionally the lock file location, that httpd and modules use
2266 to serialize access to resources. Specify <code>default</code> as
2267 the first argument to change the settings for all mutexes; specify
2268 a mutex name (see table below) as the first argument to override
2269 defaults only for that mutex.</p>
2271 <p>The <code class="directive">Mutex</code> directive is typically used in
2272 the following exceptional situations:</p>
2275 <li>change the mutex mechanism when the default mechanism selected
2276 by <a class="glossarylink" href="../glossary.html#apr" title="see glossary">APR</a> has a functional or performance
2279 <li>change the directory used by file-based mutexes when the
2280 default directory does not support locking</li>
2283 <div class="note"><h3>Supported modules</h3>
2284 <p>This directive only configures mutexes which have been registered
2285 with the core server using the <code>ap_mutex_register()</code> API.
2286 All modules bundled with httpd support the <code class="directive">Mutex</code>
2287 directive, but third-party modules may not. Consult the documentation
2288 of the third-party module, which must indicate the mutex name(s) which
2289 can be configured if this directive is supported.</p>
2292 <p>The following mutex <em>mechanisms</em> are available:</p>
2294 <li><code>default | yes</code>
2295 <p>This selects the default locking implementation, as determined by
2296 <a class="glossarylink" href="../glossary.html#apr" title="see glossary">APR</a>. The default locking implementation can
2297 be displayed by running <code class="program"><a href="../programs/httpd.html">httpd</a></code> with the
2298 <code>-V</code> option.</p></li>
2300 <li><code>none | no</code>
2301 <p>This effectively disables the mutex, and is only allowed for a
2302 mutex if the module indicates that it is a valid choice. Consult the
2303 module documentation for more information.</p></li>
2305 <li><code>posixsem</code>
2306 <p>This is a mutex variant based on a Posix semaphore.</p>
2308 <div class="warning"><h3>Warning</h3>
2309 <p>The semaphore ownership is not recovered if a thread in the process
2310 holding the mutex segfaults, resulting in a hang of the web server.</p>
2314 <li><code>sysvsem</code>
2315 <p>This is a mutex variant based on a SystemV IPC semaphore.</p>
2317 <div class="warning"><h3>Warning</h3>
2318 <p>It is possible to "leak" SysV semaphores if processes crash
2319 before the semaphore is removed.</p>
2322 <div class="warning"><h3>Security</h3>
2323 <p>The semaphore API allows for a denial of service attack by any
2324 CGIs running under the same uid as the webserver (<em>i.e.</em>,
2325 all CGIs, unless you use something like <code class="program"><a href="../programs/suexec.html">suexec</a></code>
2326 or <code>cgiwrapper</code>).</p>
2330 <li><code>sem</code>
2331 <p>This selects the "best" available semaphore implementation, choosing
2332 between Posix and SystemV IPC semaphores, in that order.</p></li>
2334 <li><code>pthread</code>
2335 <p>This is a mutex variant based on cross-process Posix thread
2338 <div class="warning"><h3>Warning</h3>
2339 <p>On most systems, if a child process terminates abnormally while
2340 holding a mutex that uses this implementation, the server will deadlock
2341 and stop responding to requests. When this occurs, the server will
2342 require a manual restart to recover.</p>
2343 <p>Solaris is a notable exception as it provides a mechanism which
2344 usually allows the mutex to be recovered after a child process
2345 terminates abnormally while holding a mutex.</p>
2346 <p>If your system implements the
2347 <code>pthread_mutexattr_setrobust_np()</code> function, you may be able
2348 to use the <code>pthread</code> option safely.</p>
2352 <li><code>fcntl:/path/to/mutex</code>
2353 <p>This is a mutex variant where a physical (lock-)file and the
2354 <code>fcntl()</code> function are used as the mutex.</p>
2356 <div class="warning"><h3>Warning</h3>
2357 <p>When multiple mutexes based on this mechanism are used within
2358 multi-threaded, multi-process environments, deadlock errors (EDEADLK)
2359 can be reported for valid mutex operations if <code>fcntl()</code>
2360 is not thread-aware, such as on Solaris.</p>
2364 <li><code>flock:/path/to/mutex</code>
2365 <p>This is similar to the <code>fcntl:/path/to/mutex</code> method
2366 with the exception that the <code>flock()</code> function is used to
2367 provide file locking.</p></li>
2369 <li><code>file:/path/to/mutex</code>
2370 <p>This selects the "best" available file locking implementation,
2371 choosing between <code>fcntl</code> and <code>flock</code>, in that
2375 <p>Most mechanisms are only available on selected platforms, where the
2376 underlying platform and <a class="glossarylink" href="../glossary.html#apr" title="see glossary">APR</a> support it. Mechanisms
2377 which aren't available on all platforms are <em>posixsem</em>,
2378 <em>sysvsem</em>, <em>sem</em>, <em>pthread</em>, <em>fcntl</em>,
2379 <em>flock</em>, and <em>file</em>.</p>
2381 <p>With the file-based mechanisms <em>fcntl</em> and <em>flock</em>,
2382 the path, if provided, is a directory where the lock file will be created.
2383 The default directory is httpd's run-time file directory relative to
2384 <code class="directive"><a href="#serverroot">ServerRoot</a></code>. Always use a local disk
2385 filesystem for <code>/path/to/mutex</code> and never a directory residing
2386 on a NFS- or AFS-filesystem. The basename of the file will be the mutex
2387 type, an optional instance string provided by the module, and unless the
2388 <code>OmitPID</code> keyword is specified, the process id of the httpd
2389 parent process will be appended to to make the file name unique, avoiding
2390 conflicts when multiple httpd instances share a lock file directory. For
2391 example, if the mutex name is <code>mpm-accept</code> and the lock file
2392 directory is <code>/var/httpd/locks</code>, the lock file name for the
2393 httpd instance with parent process id 12345 would be
2394 <code>/var/httpd/locks/mpm-accept.12345</code>.</p>
2396 <div class="warning"><h3>Security</h3>
2397 <p>It is best to <em>avoid</em> putting mutex files in a world-writable
2398 directory such as <code>/var/tmp</code> because someone could create
2399 a denial of service attack and prevent the server from starting by
2400 creating a lockfile with the same name as the one the server will try
2404 <p>The following table documents the names of mutexes used by httpd
2405 and bundled modules.</p>
2407 <table class="bordered"><tr class="header">
2410 <th>Protected resource</th>
2413 <td><code>mpm-accept</code></td>
2414 <td><code class="module"><a href="../mod/prefork.html">prefork</a></code> and <code class="module"><a href="../mod/worker.html">worker</a></code> MPMs</td>
2415 <td>incoming connections, to avoid the thundering herd problem;
2416 for more information, refer to the
2417 <a href="../misc/perf-tuning.html">performance tuning</a>
2421 <td><code>authdigest-client</code></td>
2422 <td><code class="module"><a href="../mod/mod_auth_digest.html">mod_auth_digest</a></code></td>
2423 <td>client list in shared memory</td>
2426 <td><code>authdigest-opaque</code></td>
2427 <td><code class="module"><a href="../mod/mod_auth_digest.html">mod_auth_digest</a></code></td>
2428 <td>counter in shared memory</td>
2431 <td><code>ldap-cache</code></td>
2432 <td><code class="module"><a href="../mod/mod_ldap.html">mod_ldap</a></code></td>
2433 <td>LDAP result cache</td>
2436 <td><code>rewrite-map</code></td>
2437 <td><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code></td>
2438 <td>communication with external mapping programs, to avoid
2439 intermixed I/O from multiple requests</td>
2442 <td><code>ssl-cache</code></td>
2443 <td><code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code></td>
2444 <td>SSL session cache</td>
2447 <td><code>ssl-stapling</code></td>
2448 <td><code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code></td>
2449 <td>OCSP stapling response cache</td>
2452 <td><code>watchdog-callback</code></td>
2453 <td><code class="module"><a href="../mod/mod_watchdog.html">mod_watchdog</a></code></td>
2454 <td>callback function of a particular client module</td>
2458 <p>The <code>OmitPID</code> keyword suppresses the addition of the httpd
2459 parent process id from the lock file name.</p>
2461 <p>In the following example, the mutex mechanism for the MPM accept
2462 mutex will be changed from the compiled-in default to <code>fcntl</code>,
2463 with the associated lock file created in directory
2464 <code>/var/httpd/locks</code>. The mutex mechanism for all other mutexes
2465 will be changed from the compiled-in default to <code>sysvsem</code>.</p>
2467 <div class="example"><p><code>
2468 Mutex default sysvsem<br />
2469 Mutex mpm-accept fcntl:/var/httpd/locks
2473 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2474 <div class="directive-section"><h2><a name="NameVirtualHost" id="NameVirtualHost">NameVirtualHost</a> <a name="namevirtualhost" id="namevirtualhost">Directive</a></h2>
2475 <table class="directive">
2476 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Designates an IP address for name-virtual
2478 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>NameVirtualHost <var>addr</var>[:<var>port</var>]</code></td></tr>
2479 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
2480 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2481 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2484 <p>A single <code class="directive">NameVirtualHost</code> directive
2485 identifies a set of identical virtual hosts on which the server will
2486 further select from on the basis of the <em>hostname</em>
2487 requested by the client. The <code class="directive">NameVirtualHost</code>
2488 directive is a required directive if you want to configure
2489 <a href="../vhosts/">name-based virtual hosts</a>.</p>
2491 <p>This directive, and the corresponding <code class="directive">VirtualHost</code>,
2492 <em>must</em> be qualified with a port number if the server supports both HTTP
2493 and HTTPS connections.</p>
2495 <p>Although <var>addr</var> can be a hostname, it is recommended
2496 that you always use an IP address or a wildcard. A wildcard
2497 NameVirtualHost matches only virtualhosts that also have a literal wildcard
2498 as their argument.</p>
2500 <p>In cases where a firewall or other proxy receives the requests and
2501 forwards them on a different IP address to the server, you must specify the
2502 IP address of the physical interface on the machine which will be
2503 servicing the requests. </p>
2505 <p> In the example below, requests received on interface 192.0.2.1 and port 80
2506 will only select among the first two virtual hosts. Requests received on
2507 port 80 on any other interface will only select among the third and fourth
2508 virtual hosts. In the common case where the interface isn't important
2509 to the mapping, only the "*:80" NameVirtualHost and VirtualHost directives
2512 <div class="example"><p><code>
2513 NameVirtualHost 192.0.2.1:80<br />
2514 NameVirtualHost *:80<br /><br />
2516 <VirtualHost 192.0.2.1:80><br />
2517 ServerName namebased-a.example.com<br />
2518 </VirtualHost><br />
2520 <VirtualHost 192.0.2.1:80><br />
2521 Servername namebased-b.example.com<br />
2522 </VirtualHost><br />
2524 <VirtualHost *:80><br />
2525 ServerName namebased-c.example.com <br />
2526 </VirtualHost><br />
2528 <VirtualHost *:80><br />
2529 ServerName namebased-d.example.com <br />
2530 </VirtualHost><br />
2535 <p>IPv6 addresses must be enclosed in square brackets, as shown
2536 in the following example:</p>
2538 <div class="example"><p><code>
2539 NameVirtualHost [2001:db8::a00:20ff:fea7:ccea]:8080
2542 <div class="note"><h3>Argument to <code class="directive"><VirtualHost></code>
2544 <p>Note that the argument to the <code class="directive"><VirtualHost></code> directive must
2545 exactly match the argument to the <code class="directive">NameVirtualHost</code> directive.</p>
2547 <div class="example"><p><code>
2548 NameVirtualHost 192.0.2.2:80<br />
2549 <VirtualHost 192.0.2.2:80><br />
2551 </VirtualHost><br />
2557 <li><a href="../vhosts/">Virtual Hosts
2558 documentation</a></li>
2561 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2562 <div class="directive-section"><h2><a name="Options" id="Options">Options</a> <a name="options" id="options">Directive</a></h2>
2563 <table class="directive">
2564 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures what features are available in a particular
2566 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Options
2567 [+|-]<var>option</var> [[+|-]<var>option</var>] ...</code></td></tr>
2568 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Options All</code></td></tr>
2569 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
2570 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Options</td></tr>
2571 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2572 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2574 <p>The <code class="directive">Options</code> directive controls which
2575 server features are available in a particular directory.</p>
2577 <p><var>option</var> can be set to <code>None</code>, in which
2578 case none of the extra features are enabled, or one or more of
2582 <dt><code>All</code></dt>
2584 <dd>All options except for <code>MultiViews</code>. This is the default
2587 <dt><code>ExecCGI</code></dt>
2590 Execution of CGI scripts using <code class="module"><a href="../mod/mod_cgi.html">mod_cgi</a></code>
2593 <dt><code>FollowSymLinks</code></dt>
2597 The server will follow symbolic links in this directory.
2599 <p>Even though the server follows the symlink it does <em>not</em>
2600 change the pathname used to match against <code class="directive"><a href="#directory"><Directory></a></code> sections.</p>
2601 <p>Note also, that this option <strong>gets ignored</strong> if set
2602 inside a <code class="directive"><a href="#location"><Location></a></code>
2604 <p>Omitting this option should not be considered a security restriction,
2605 since symlink testing is subject to race conditions that make it
2609 <dt><code>Includes</code></dt>
2612 Server-side includes provided by <code class="module"><a href="../mod/mod_include.html">mod_include</a></code>
2615 <dt><code>IncludesNOEXEC</code></dt>
2619 Server-side includes are permitted, but the <code>#exec
2620 cmd</code> and <code>#exec cgi</code> are disabled. It is still
2621 possible to <code>#include virtual</code> CGI scripts from
2622 <code class="directive"><a href="../mod/mod_alias.html#scriptalias">ScriptAlias</a></code>ed
2625 <dt><code>Indexes</code></dt>
2628 If a URL which maps to a directory is requested, and there
2629 is no <code class="directive"><a href="../mod/mod_dir.html#directoryindex">DirectoryIndex</a></code>
2630 (<em>e.g.</em>, <code>index.html</code>) in that directory, then
2631 <code class="module"><a href="../mod/mod_autoindex.html">mod_autoindex</a></code> will return a formatted listing
2632 of the directory.</dd>
2634 <dt><code>MultiViews</code></dt>
2637 <a href="../content-negotiation.html">Content negotiated</a>
2638 "MultiViews" are allowed using
2639 <code class="module"><a href="../mod/mod_negotiation.html">mod_negotiation</a></code>.</dd>
2641 <dt><code>SymLinksIfOwnerMatch</code></dt>
2643 <dd>The server will only follow symbolic links for which the
2644 target file or directory is owned by the same user id as the
2647 <div class="note"><h3>Note</h3> <p>This option gets ignored if
2648 set inside a <code class="directive"><a href="#location"><Location></a></code> section.</p>
2649 <p>This option should not be considered a security restriction,
2650 since symlink testing is subject to race conditions that make it
2651 circumventable.</p></div>
2655 <p>Normally, if multiple <code class="directive">Options</code> could
2656 apply to a directory, then the most specific one is used and
2657 others are ignored; the options are not merged. (See <a href="../sections.html#mergin">how sections are merged</a>.)
2658 However if <em>all</em> the options on the
2659 <code class="directive">Options</code> directive are preceded by a
2660 <code>+</code> or <code>-</code> symbol, the options are
2661 merged. Any options preceded by a <code>+</code> are added to the
2662 options currently in force, and any options preceded by a
2663 <code>-</code> are removed from the options currently in
2666 <div class="warning"><h3>Warning</h3>
2667 <p>Mixing <code class="directive">Options</code> with a <code>+</code> or
2668 <code>-</code> with those without is not valid syntax, and is likely
2669 to cause unexpected results.</p>
2672 <p>For example, without any <code>+</code> and <code>-</code> symbols:</p>
2674 <div class="example"><p><code>
2675 <Directory /web/docs><br />
2676 <span class="indent">
2677 Options Indexes FollowSymLinks<br />
2679 </Directory><br />
2681 <Directory /web/docs/spec><br />
2682 <span class="indent">
2683 Options Includes<br />
2688 <p>then only <code>Includes</code> will be set for the
2689 <code>/web/docs/spec</code> directory. However if the second
2690 <code class="directive">Options</code> directive uses the <code>+</code> and
2691 <code>-</code> symbols:</p>
2693 <div class="example"><p><code>
2694 <Directory /web/docs><br />
2695 <span class="indent">
2696 Options Indexes FollowSymLinks<br />
2698 </Directory><br />
2700 <Directory /web/docs/spec><br />
2701 <span class="indent">
2702 Options +Includes -Indexes<br />
2707 <p>then the options <code>FollowSymLinks</code> and
2708 <code>Includes</code> are set for the <code>/web/docs/spec</code>
2711 <div class="note"><h3>Note</h3>
2712 <p>Using <code>-IncludesNOEXEC</code> or
2713 <code>-Includes</code> disables server-side includes completely
2714 regardless of the previous setting.</p>
2717 <p>The default in the absence of any other settings is
2718 <code>All</code>.</p>
2721 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2722 <div class="directive-section"><h2><a name="RLimitCPU" id="RLimitCPU">RLimitCPU</a> <a name="rlimitcpu" id="rlimitcpu">Directive</a></h2>
2723 <table class="directive">
2724 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the CPU consumption of processes launched
2725 by Apache children</td></tr>
2726 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitCPU <var>seconds</var>|max [<var>seconds</var>|max]</code></td></tr>
2727 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
2728 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
2729 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
2730 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2731 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2733 <p>Takes 1 or 2 parameters. The first parameter sets the soft
2734 resource limit for all processes and the second parameter sets
2735 the maximum resource limit. Either parameter can be a number,
2736 or <code>max</code> to indicate to the server that the limit should
2737 be set to the maximum allowed by the operating system
2738 configuration. Raising the maximum resource limit requires that
2739 the server is running as <code>root</code>, or in the initial startup
2742 <p>This applies to processes forked off from Apache children
2743 servicing requests, not the Apache children themselves. This
2744 includes CGI scripts and SSI exec commands, but not any
2745 processes forked off from the Apache parent such as piped
2748 <p>CPU resource limits are expressed in seconds per
2753 <li><code class="directive"><a href="#rlimitmem">RLimitMEM</a></code></li>
2754 <li><code class="directive"><a href="#rlimitnproc">RLimitNPROC</a></code></li>
2757 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2758 <div class="directive-section"><h2><a name="RLimitMEM" id="RLimitMEM">RLimitMEM</a> <a name="rlimitmem" id="rlimitmem">Directive</a></h2>
2759 <table class="directive">
2760 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the memory consumption of processes launched
2761 by Apache children</td></tr>
2762 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitMEM <var>bytes</var>|max [<var>bytes</var>|max]</code></td></tr>
2763 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
2764 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
2765 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
2766 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2767 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2769 <p>Takes 1 or 2 parameters. The first parameter sets the soft
2770 resource limit for all processes and the second parameter sets
2771 the maximum resource limit. Either parameter can be a number,
2772 or <code>max</code> to indicate to the server that the limit should
2773 be set to the maximum allowed by the operating system
2774 configuration. Raising the maximum resource limit requires that
2775 the server is running as <code>root</code>, or in the initial startup
2778 <p>This applies to processes forked off from Apache children
2779 servicing requests, not the Apache children themselves. This
2780 includes CGI scripts and SSI exec commands, but not any
2781 processes forked off from the Apache parent such as piped
2784 <p>Memory resource limits are expressed in bytes per
2789 <li><code class="directive"><a href="#rlimitcpu">RLimitCPU</a></code></li>
2790 <li><code class="directive"><a href="#rlimitnproc">RLimitNPROC</a></code></li>
2793 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2794 <div class="directive-section"><h2><a name="RLimitNPROC" id="RLimitNPROC">RLimitNPROC</a> <a name="rlimitnproc" id="rlimitnproc">Directive</a></h2>
2795 <table class="directive">
2796 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the number of processes that can be launched by
2797 processes launched by Apache children</td></tr>
2798 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitNPROC <var>number</var>|max [<var>number</var>|max]</code></td></tr>
2799 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
2800 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
2801 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
2802 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2803 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2805 <p>Takes 1 or 2 parameters. The first parameter sets the soft
2806 resource limit for all processes and the second parameter sets
2807 the maximum resource limit. Either parameter can be a number,
2808 or <code>max</code> to indicate to the server that the limit
2809 should be set to the maximum allowed by the operating system
2810 configuration. Raising the maximum resource limit requires that
2811 the server is running as <code>root</code>, or in the initial startup
2814 <p>This applies to processes forked off from Apache children
2815 servicing requests, not the Apache children themselves. This
2816 includes CGI scripts and SSI exec commands, but not any
2817 processes forked off from the Apache parent such as piped
2820 <p>Process limits control the number of processes per user.</p>
2822 <div class="note"><h3>Note</h3>
2823 <p>If CGI processes are <strong>not</strong> running
2824 under user ids other than the web server user id, this directive
2825 will limit the number of processes that the server itself can
2826 create. Evidence of this situation will be indicated by
2827 <strong><code>cannot fork</code></strong> messages in the
2828 <code>error_log</code>.</p>
2833 <li><code class="directive"><a href="#rlimitmem">RLimitMEM</a></code></li>
2834 <li><code class="directive"><a href="#rlimitcpu">RLimitCPU</a></code></li>
2837 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2838 <div class="directive-section"><h2><a name="ScriptInterpreterSource" id="ScriptInterpreterSource">ScriptInterpreterSource</a> <a name="scriptinterpretersource" id="scriptinterpretersource">Directive</a></h2>
2839 <table class="directive">
2840 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Technique for locating the interpreter for CGI
2842 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScriptInterpreterSource Registry|Registry-Strict|Script</code></td></tr>
2843 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScriptInterpreterSource Script</code></td></tr>
2844 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
2845 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
2846 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2847 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2848 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Win32 only;
2849 option <code>Registry-Strict</code> is available in Apache 2.0 and
2852 <p>This directive is used to control how Apache finds the
2853 interpreter used to run CGI scripts. The default setting is
2854 <code>Script</code>. This causes Apache to use the interpreter pointed to
2855 by the shebang line (first line, starting with <code>#!</code>) in the
2856 script. On Win32 systems this line usually looks like:</p>
2858 <div class="example"><p><code>
2859 #!C:/Perl/bin/perl.exe
2862 <p>or, if <code>perl</code> is in the <code>PATH</code>, simply:</p>
2864 <div class="example"><p><code>
2868 <p>Setting <code>ScriptInterpreterSource Registry</code> will
2869 cause the Windows Registry tree <code>HKEY_CLASSES_ROOT</code> to be
2870 searched using the script file extension (e.g., <code>.pl</code>) as a
2871 search key. The command defined by the registry subkey
2872 <code>Shell\ExecCGI\Command</code> or, if it does not exist, by the subkey
2873 <code>Shell\Open\Command</code> is used to open the script file. If the
2874 registry keys cannot be found, Apache falls back to the behavior of the
2875 <code>Script</code> option.</p>
2877 <div class="warning"><h3>Security</h3>
2878 <p>Be careful when using <code>ScriptInterpreterSource
2879 Registry</code> with <code class="directive"><a href="../mod/mod_alias.html#scriptalias">ScriptAlias</a></code>'ed directories, because
2880 Apache will try to execute <strong>every</strong> file within this
2881 directory. The <code>Registry</code> setting may cause undesired
2882 program calls on files which are typically not executed. For
2883 example, the default open command on <code>.htm</code> files on
2884 most Windows systems will execute Microsoft Internet Explorer, so
2885 any HTTP request for an <code>.htm</code> file existing within the
2886 script directory would start the browser in the background on the
2887 server. This is a good way to crash your system within a minute or
2891 <p>The option <code>Registry-Strict</code> which is new in Apache
2892 2.0 does the same thing as <code>Registry</code> but uses only the
2893 subkey <code>Shell\ExecCGI\Command</code>. The
2894 <code>ExecCGI</code> key is not a common one. It must be
2895 configured manually in the windows registry and hence prevents
2896 accidental program calls on your system.</p>
2899 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2900 <div class="directive-section"><h2><a name="ServerAdmin" id="ServerAdmin">ServerAdmin</a> <a name="serveradmin" id="serveradmin">Directive</a></h2>
2901 <table class="directive">
2902 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Email address that the server includes in error
2903 messages sent to the client</td></tr>
2904 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerAdmin <var>email-address</var>|<var>URL</var></code></td></tr>
2905 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
2906 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2907 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2909 <p>The <code class="directive">ServerAdmin</code> sets the contact address
2910 that the server includes in any error messages it returns to the
2911 client. If the <code>httpd</code> doesn't recognize the supplied argument
2913 assumes, that it's an <var>email-address</var> and prepends it with
2914 <code>mailto:</code> in hyperlink targets. However, it's recommended to
2915 actually use an email address, since there are a lot of CGI scripts that
2916 make that assumption. If you want to use an URL, it should point to another
2917 server under your control. Otherwise users may not be able to contact you in
2920 <p>It may be worth setting up a dedicated address for this, e.g.</p>
2922 <div class="example"><p><code>
2923 ServerAdmin www-admin@foo.example.com
2925 <p>as users do not always mention that they are talking about the
2929 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2930 <div class="directive-section"><h2><a name="ServerAlias" id="ServerAlias">ServerAlias</a> <a name="serveralias" id="serveralias">Directive</a></h2>
2931 <table class="directive">
2932 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Alternate names for a host used when matching requests
2933 to name-virtual hosts</td></tr>
2934 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerAlias <var>hostname</var> [<var>hostname</var>] ...</code></td></tr>
2935 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>virtual host</td></tr>
2936 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2937 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2939 <p>The <code class="directive">ServerAlias</code> directive sets the
2940 alternate names for a host, for use with <a href="../vhosts/name-based.html">name-based virtual hosts</a>. The
2941 <code class="directive">ServerAlias</code> may include wildcards, if appropriate.</p>
2943 <div class="example"><p><code>
2944 <VirtualHost *:80><br />
2945 ServerName server.domain.com<br />
2946 ServerAlias server server2.domain.com server2<br />
2947 ServerAlias *.example.com<br />
2949 </VirtualHost>
2954 <li><a href="../vhosts/">Apache Virtual Host documentation</a></li>
2957 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
2958 <div class="directive-section"><h2><a name="ServerName" id="ServerName">ServerName</a> <a name="servername" id="servername">Directive</a></h2>
2959 <table class="directive">
2960 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Hostname and port that the server uses to identify
2962 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerName [<var>scheme</var>://]<var>fully-qualified-domain-name</var>[:<var>port</var>]</code></td></tr>
2963 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
2964 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
2965 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
2966 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>In version 2.0, this
2967 directive supersedes the functionality of the <code class="directive">Port</code>
2968 directive from version 1.3.</td></tr>
2970 <p>The <code class="directive">ServerName</code> directive sets the
2971 request scheme, hostname and
2972 port that the server uses to identify itself. This is used when
2973 creating redirection URLs. For example, if the name of the
2974 machine hosting the web server is <code>simple.example.com</code>,
2975 but the machine also has the DNS alias <code>www.example.com</code>
2976 and you wish the web server to be so identified, the following
2977 directive should be used:</p>
2979 <div class="example"><p><code>
2980 ServerName www.example.com:80
2983 <p>If no <code class="directive">ServerName</code> is specified, then the
2984 server attempts to deduce the hostname by performing a reverse
2985 lookup on the IP address. If no port is specified in the
2986 <code class="directive">ServerName</code>, then the server will use the
2987 port from the incoming request. For optimal reliability and
2988 predictability, you should specify an explicit hostname and port
2989 using the <code class="directive">ServerName</code> directive.</p>
2991 <p>If you are using <a href="../vhosts/name-based.html">name-based virtual hosts</a>,
2992 the <code class="directive">ServerName</code> inside a
2993 <code class="directive"><a href="#virtualhost"><VirtualHost></a></code>
2994 section specifies what hostname must appear in the request's
2995 <code>Host:</code> header to match this virtual host.</p>
2998 <p>Sometimes, the server runs behind a device that processes SSL,
2999 such as a reverse proxy, load balancer or SSL offload
3000 appliance. When this is the case, specify the
3001 <code>https://</code> scheme and the port number to which the
3002 clients connect in the <code class="directive">ServerName</code> directive
3003 to make sure that the server generates the correct
3004 self-referential URLs.
3007 <p>See the description of the
3008 <code class="directive"><a href="#usecanonicalname">UseCanonicalName</a></code> and
3009 <code class="directive"><a href="#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></code> directives for
3010 settings which determine whether self-referential URLs (e.g., by the
3011 <code class="module"><a href="../mod/mod_dir.html">mod_dir</a></code> module) will refer to the
3012 specified port, or to the port number given in the client's request.
3018 <li><a href="../dns-caveats.html">Issues Regarding DNS and
3020 <li><a href="../vhosts/">Apache virtual host
3021 documentation</a></li>
3022 <li><code class="directive"><a href="#usecanonicalname">UseCanonicalName</a></code></li>
3023 <li><code class="directive"><a href="#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></code></li>
3024 <li><code class="directive"><a href="#namevirtualhost">NameVirtualHost</a></code></li>
3025 <li><code class="directive"><a href="#serveralias">ServerAlias</a></code></li>
3028 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3029 <div class="directive-section"><h2><a name="ServerPath" id="ServerPath">ServerPath</a> <a name="serverpath" id="serverpath">Directive</a></h2>
3030 <table class="directive">
3031 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Legacy URL pathname for a name-based virtual host that
3032 is accessed by an incompatible browser</td></tr>
3033 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerPath <var>URL-path</var></code></td></tr>
3034 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>virtual host</td></tr>
3035 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3036 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3038 <p>The <code class="directive">ServerPath</code> directive sets the legacy
3039 URL pathname for a host, for use with <a href="../vhosts/">name-based virtual hosts</a>.</p>
3043 <li><a href="../vhosts/">Apache Virtual Host documentation</a></li>
3046 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3047 <div class="directive-section"><h2><a name="ServerRoot" id="ServerRoot">ServerRoot</a> <a name="serverroot" id="serverroot">Directive</a></h2>
3048 <table class="directive">
3049 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Base directory for the server installation</td></tr>
3050 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerRoot <var>directory-path</var></code></td></tr>
3051 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ServerRoot /usr/local/apache</code></td></tr>
3052 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
3053 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3054 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3056 <p>The <code class="directive">ServerRoot</code> directive sets the
3057 directory in which the server lives. Typically it will contain the
3058 subdirectories <code>conf/</code> and <code>logs/</code>. Relative
3059 paths in other configuration directives (such as <code class="directive"><a href="#include">Include</a></code> or <code class="directive"><a href="../mod/mod_so.html#loadmodule">LoadModule</a></code>, for example) are taken as
3060 relative to this directory.</p>
3062 <div class="example"><h3>Example</h3><p><code>
3063 ServerRoot /home/httpd
3069 <li><a href="../invoking.html">the <code>-d</code>
3070 option to <code>httpd</code></a></li>
3071 <li><a href="../misc/security_tips.html#serverroot">the
3072 security tips</a> for information on how to properly set
3073 permissions on the <code class="directive">ServerRoot</code></li>
3076 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3077 <div class="directive-section"><h2><a name="ServerSignature" id="ServerSignature">ServerSignature</a> <a name="serversignature" id="serversignature">Directive</a></h2>
3078 <table class="directive">
3079 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures the footer on server-generated documents</td></tr>
3080 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerSignature On|Off|EMail</code></td></tr>
3081 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ServerSignature Off</code></td></tr>
3082 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
3083 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
3084 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3085 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3087 <p>The <code class="directive">ServerSignature</code> directive allows the
3088 configuration of a trailing footer line under server-generated
3089 documents (error messages, <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> ftp directory
3090 listings, <code class="module"><a href="../mod/mod_info.html">mod_info</a></code> output, ...). The reason why you
3091 would want to enable such a footer line is that in a chain of proxies,
3092 the user often has no possibility to tell which of the chained servers
3093 actually produced a returned error message.</p>
3095 <p>The <code>Off</code>
3096 setting, which is the default, suppresses the footer line (and is
3097 therefore compatible with the behavior of Apache-1.2 and
3098 below). The <code>On</code> setting simply adds a line with the
3099 server version number and <code class="directive"><a href="#servername">ServerName</a></code> of the serving virtual host,
3100 and the <code>EMail</code> setting additionally creates a
3101 "mailto:" reference to the <code class="directive"><a href="#serveradmin">ServerAdmin</a></code> of the referenced
3104 <p>After version 2.0.44, the details of the server version number
3105 presented are controlled by the <code class="directive"><a href="#servertokens">ServerTokens</a></code> directive.</p>
3109 <li><code class="directive"><a href="#servertokens">ServerTokens</a></code></li>
3112 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3113 <div class="directive-section"><h2><a name="ServerTokens" id="ServerTokens">ServerTokens</a> <a name="servertokens" id="servertokens">Directive</a></h2>
3114 <table class="directive">
3115 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures the <code>Server</code> HTTP response
3117 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerTokens Major|Minor|Min[imal]|Prod[uctOnly]|OS|Full</code></td></tr>
3118 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ServerTokens Full</code></td></tr>
3119 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
3120 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3121 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3123 <p>This directive controls whether <code>Server</code> response
3124 header field which is sent back to clients includes a
3125 description of the generic OS-type of the server as well as
3126 information about compiled-in modules.</p>
3129 <dt><code>ServerTokens Full</code> (or not specified)</dt>
3131 <dd>Server sends (<em>e.g.</em>): <code>Server: Apache/2.4.1
3132 (Unix) PHP/4.2.2 MyMod/1.2</code></dd>
3134 <dt><code>ServerTokens Prod[uctOnly]</code></dt>
3136 <dd>Server sends (<em>e.g.</em>): <code>Server:
3139 <dt><code>ServerTokens Major</code></dt>
3141 <dd>Server sends (<em>e.g.</em>): <code>Server:
3142 Apache/2</code></dd>
3144 <dt><code>ServerTokens Minor</code></dt>
3146 <dd>Server sends (<em>e.g.</em>): <code>Server:
3147 Apache/2.4</code></dd>
3149 <dt><code>ServerTokens Min[imal]</code></dt>
3151 <dd>Server sends (<em>e.g.</em>): <code>Server:
3152 Apache/2.4.1</code></dd>
3154 <dt><code>ServerTokens OS</code></dt>
3156 <dd>Server sends (<em>e.g.</em>): <code>Server: Apache/2.4.1
3161 <p>This setting applies to the entire server, and cannot be
3162 enabled or disabled on a virtualhost-by-virtualhost basis.</p>
3164 <p>After version 2.0.44, this directive also controls the
3165 information presented by the <code class="directive"><a href="#serversignature">ServerSignature</a></code> directive.</p>
3167 <div class="note">Setting <code class="directive">ServerTokens</code> to less than
3168 <code>minimal</code> is not recommended because it makes it more
3169 difficult to debug interoperational problems. Also note that
3170 disabling the Server: header does nothing at all to make your
3171 server more secure; the idea of "security through obscurity"
3172 is a myth and leads to a false sense of safety.</div>
3177 <li><code class="directive"><a href="#serversignature">ServerSignature</a></code></li>
3180 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3181 <div class="directive-section"><h2><a name="SetHandler" id="SetHandler">SetHandler</a> <a name="sethandler" id="sethandler">Directive</a></h2>
3182 <table class="directive">
3183 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Forces all matching files to be processed by a
3185 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SetHandler <var>handler-name</var>|None</code></td></tr>
3186 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
3187 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
3188 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3189 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3190 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Moved into the core in Apache 2.0</td></tr>
3192 <p>When placed into an <code>.htaccess</code> file or a
3193 <code class="directive"><a href="#directory"><Directory></a></code> or
3194 <code class="directive"><a href="#location"><Location></a></code>
3195 section, this directive forces all matching files to be parsed
3196 through the <a href="../handler.html">handler</a> given by
3197 <var>handler-name</var>. For example, if you had a directory you
3198 wanted to be parsed entirely as imagemap rule files, regardless
3199 of extension, you might put the following into an
3200 <code>.htaccess</code> file in that directory:</p>
3202 <div class="example"><p><code>
3203 SetHandler imap-file
3206 <p>Another example: if you wanted to have the server display a
3207 status report whenever a URL of
3208 <code>http://servername/status</code> was called, you might put
3209 the following into <code>httpd.conf</code>:</p>
3211 <div class="example"><p><code>
3212 <Location /status><br />
3213 <span class="indent">
3214 SetHandler server-status<br />
3219 <p>You can override an earlier defined <code class="directive">SetHandler</code>
3220 directive by using the value <code>None</code>.</p>
3221 <p><strong>Note:</strong> because SetHandler overrides default handlers,
3222 normal behaviour such as handling of URLs ending in a slash (/) as
3223 directories or index files is suppressed.</p>
3227 <li><code class="directive"><a href="../mod/mod_mime.html#addhandler">AddHandler</a></code></li>
3230 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3231 <div class="directive-section"><h2><a name="SetInputFilter" id="SetInputFilter">SetInputFilter</a> <a name="setinputfilter" id="setinputfilter">Directive</a></h2>
3232 <table class="directive">
3233 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the filters that will process client requests and POST
3235 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SetInputFilter <var>filter</var>[;<var>filter</var>...]</code></td></tr>
3236 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
3237 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
3238 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3239 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3241 <p>The <code class="directive">SetInputFilter</code> directive sets the
3242 filter or filters which will process client requests and POST
3243 input when they are received by the server. This is in addition to
3244 any filters defined elsewhere, including the
3245 <code class="directive"><a href="../mod/mod_mime.html#addinputfilter">AddInputFilter</a></code>
3248 <p>If more than one filter is specified, they must be separated
3249 by semicolons in the order in which they should process the
3254 <li><a href="../filter.html">Filters</a> documentation</li>
3257 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3258 <div class="directive-section"><h2><a name="SetOutputFilter" id="SetOutputFilter">SetOutputFilter</a> <a name="setoutputfilter" id="setoutputfilter">Directive</a></h2>
3259 <table class="directive">
3260 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the filters that will process responses from the
3262 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SetOutputFilter <var>filter</var>[;<var>filter</var>...]</code></td></tr>
3263 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
3264 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
3265 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3266 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3268 <p>The <code class="directive">SetOutputFilter</code> directive sets the filters
3269 which will process responses from the server before they are
3270 sent to the client. This is in addition to any filters defined
3271 elsewhere, including the
3272 <code class="directive"><a href="../mod/mod_mime.html#addoutputfilter">AddOutputFilter</a></code>
3275 <p>For example, the following configuration will process all files
3276 in the <code>/www/data/</code> directory for server-side
3279 <div class="example"><p><code>
3280 <Directory /www/data/><br />
3281 <span class="indent">
3282 SetOutputFilter INCLUDES<br />
3287 <p>If more than one filter is specified, they must be separated
3288 by semicolons in the order in which they should process the
3293 <li><a href="../filter.html">Filters</a> documentation</li>
3296 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3297 <div class="directive-section"><h2><a name="TimeOut" id="TimeOut">TimeOut</a> <a name="timeout" id="timeout">Directive</a></h2>
3298 <table class="directive">
3299 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Amount of time the server will wait for
3300 certain events before failing a request</td></tr>
3301 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>TimeOut <var>seconds</var></code></td></tr>
3302 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>TimeOut 300</code></td></tr>
3303 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
3304 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3305 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3307 <p>The <code class="directive">TimeOut</code> directive defines the length
3308 of time Apache will wait for I/O in various circumstances:</p>
3311 <li>When reading data from the client, the length of time to
3312 wait for a TCP packet to arrive if the read buffer is
3315 <li>When writing data to the client, the length of time to wait
3316 for an acknowledgement of a packet if the send buffer is
3319 <li>In <code class="module"><a href="../mod/mod_cgi.html">mod_cgi</a></code>, the length of time to wait for
3320 output from a CGI script.</li>
3322 <li>In <code class="module"><a href="../mod/mod_ext_filter.html">mod_ext_filter</a></code>, the length of time to
3323 wait for output from a filtering process.</li>
3325 <li>In <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>, the default timeout value if
3326 <code class="directive"><a href="../mod/mod_proxy.html#proxytimeout">ProxyTimeout</a></code> is not
3332 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3333 <div class="directive-section"><h2><a name="TraceEnable" id="TraceEnable">TraceEnable</a> <a name="traceenable" id="traceenable">Directive</a></h2>
3334 <table class="directive">
3335 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determines the behaviour on <code>TRACE</code>
3337 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>TraceEnable <var>[on|off|extended]</var></code></td></tr>
3338 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>TraceEnable on</code></td></tr>
3339 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
3340 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3341 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3342 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 1.3.34, 2.0.55 and later</td></tr>
3344 <p>This directive overrides the behavior of <code>TRACE</code> for both
3345 the core server and <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>. The default
3346 <code>TraceEnable on</code> permits <code>TRACE</code> requests per
3347 RFC 2616, which disallows any request body to accompany the request.
3348 <code>TraceEnable off</code> causes the core server and
3349 <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> to return a <code>405</code> (Method not
3350 allowed) error to the client.</p>
3352 <p>Finally, for testing and diagnostic purposes only, request
3353 bodies may be allowed using the non-compliant <code>TraceEnable
3354 extended</code> directive. The core (as an origin server) will
3355 restrict the request body to 64k (plus 8k for chunk headers if
3356 <code>Transfer-Encoding: chunked</code> is used). The core will
3357 reflect the full headers and all chunk headers with the response
3358 body. As a proxy server, the request body is not restricted to 64k.</p>
3361 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3362 <div class="directive-section"><h2><a name="UseCanonicalName" id="UseCanonicalName">UseCanonicalName</a> <a name="usecanonicalname" id="usecanonicalname">Directive</a></h2>
3363 <table class="directive">
3364 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures how the server determines its own name and
3366 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>UseCanonicalName On|Off|DNS</code></td></tr>
3367 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>UseCanonicalName Off</code></td></tr>
3368 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
3369 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3370 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3372 <p>In many situations Apache must construct a <em>self-referential</em>
3373 URL -- that is, a URL that refers back to the same server. With
3374 <code>UseCanonicalName On</code> Apache will use the hostname and port
3375 specified in the <code class="directive"><a href="#servername">ServerName</a></code>
3376 directive to construct the canonical name for the server. This name
3377 is used in all self-referential URLs, and for the values of
3378 <code>SERVER_NAME</code> and <code>SERVER_PORT</code> in CGIs.</p>
3380 <p>With <code>UseCanonicalName Off</code> Apache will form
3381 self-referential URLs using the hostname and port supplied by
3382 the client if any are supplied (otherwise it will use the
3383 canonical name, as defined above). These values are the same
3384 that are used to implement <a href="../vhosts/name-based.html">name based virtual hosts</a>,
3385 and are available with the same clients. The CGI variables
3386 <code>SERVER_NAME</code> and <code>SERVER_PORT</code> will be
3387 constructed from the client supplied values as well.</p>
3389 <p>An example where this may be useful is on an intranet server
3390 where you have users connecting to the machine using short
3391 names such as <code>www</code>. You'll notice that if the users
3392 type a shortname, and a URL which is a directory, such as
3393 <code>http://www/splat</code>, <em>without the trailing
3394 slash</em> then Apache will redirect them to
3395 <code>http://www.domain.com/splat/</code>. If you have
3396 authentication enabled, this will cause the user to have to
3397 authenticate twice (once for <code>www</code> and once again
3398 for <code>www.domain.com</code> -- see <a href="http://httpd.apache.org/docs/misc/FAQ.html#prompted-twice">the
3399 FAQ on this subject for more information</a>). But if
3400 <code class="directive">UseCanonicalName</code> is set <code>Off</code>, then
3401 Apache will redirect to <code>http://www/splat/</code>.</p>
3403 <p>There is a third option, <code>UseCanonicalName DNS</code>,
3404 which is intended for use with mass IP-based virtual hosting to
3405 support ancient clients that do not provide a
3406 <code>Host:</code> header. With this option Apache does a
3407 reverse DNS lookup on the server IP address that the client
3408 connected to in order to work out self-referential URLs.</p>
3410 <div class="warning"><h3>Warning</h3>
3411 <p>If CGIs make assumptions about the values of <code>SERVER_NAME</code>
3412 they may be broken by this option. The client is essentially free
3413 to give whatever value they want as a hostname. But if the CGI is
3414 only using <code>SERVER_NAME</code> to construct self-referential URLs
3415 then it should be just fine.</p>
3420 <li><code class="directive"><a href="#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></code></li>
3421 <li><code class="directive"><a href="#servername">ServerName</a></code></li>
3422 <li><code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code></li>
3425 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3426 <div class="directive-section"><h2><a name="UseCanonicalPhysicalPort" id="UseCanonicalPhysicalPort">UseCanonicalPhysicalPort</a> <a name="usecanonicalphysicalport" id="usecanonicalphysicalport">Directive</a></h2>
3427 <table class="directive">
3428 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures how the server determines its own name and
3430 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>UseCanonicalPhysicalPort On|Off</code></td></tr>
3431 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>UseCanonicalPhysicalPort Off</code></td></tr>
3432 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
3433 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3434 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3436 <p>In many situations Apache must construct a <em>self-referential</em>
3437 URL -- that is, a URL that refers back to the same server. With
3438 <code>UseCanonicalPhysicalPort On</code> Apache will, when
3439 constructing the canonical port for the server to honor
3440 the <code class="directive"><a href="#usecanonicalname">UseCanonicalName</a></code> directive,
3441 provide the actual physical port number being used by this request
3442 as a potential port. With <code>UseCanonicalPhysicalPort Off</code>
3443 Apache will not ever use the actual physical port number, instead
3444 relying on all configured information to construct a valid port number.</p>
3446 <div class="note"><h3>Note</h3>
3447 <p>The ordering of when the physical port is used is as follows:<br /><br />
3448 <code>UseCanonicalName On</code></p>
3450 <li>Port provided in <code>Servername</code></li>
3451 <li>Physical port</li>
3452 <li>Default port</li>
3454 <code>UseCanonicalName Off | DNS</code>
3456 <li>Parsed port from <code>Host:</code> header</li>
3457 <li>Physical port</li>
3458 <li>Port provided in <code>Servername</code></li>
3459 <li>Default port</li>
3462 <p>With <code>UseCanonicalPhysicalPort Off</code>, the
3463 physical ports are removed from the ordering.</p>
3469 <li><code class="directive"><a href="#usecanonicalname">UseCanonicalName</a></code></li>
3470 <li><code class="directive"><a href="#servername">ServerName</a></code></li>
3471 <li><code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code></li>
3474 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
3475 <div class="directive-section"><h2><a name="VirtualHost" id="VirtualHost"><VirtualHost></a> <a name="virtualhost" id="virtualhost">Directive</a></h2>
3476 <table class="directive">
3477 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Contains directives that apply only to a specific
3478 hostname or IP address</td></tr>
3479 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><VirtualHost
3480 <var>addr</var>[:<var>port</var>] [<var>addr</var>[:<var>port</var>]]
3481 ...> ... </VirtualHost></code></td></tr>
3482 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
3483 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
3484 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
3486 <p><code class="directive"><VirtualHost></code> and
3487 <code></VirtualHost></code> are used to enclose a group of
3488 directives that will apply only to a particular virtual host. Any
3489 directive that is allowed in a virtual host context may be
3490 used. When the server receives a request for a document on a
3491 particular virtual host, it uses the configuration directives
3492 enclosed in the <code class="directive"><VirtualHost></code>
3493 section. <var>Addr</var> can be:</p>
3496 <li>The IP address of the virtual host;</li>
3498 <li>A fully qualified domain name for the IP address of the
3499 virtual host (not recommended);</li>
3501 <li>The character <code>*</code>, which is used only in combination with
3502 <code>NameVirtualHost *</code> to match all IP addresses; or</li>
3504 <li>The string <code>_default_</code>, which is used only
3505 with IP virtual hosting to catch unmatched IP addresses.</li>
3508 <div class="example"><h3>Example</h3><p><code>
3509 <VirtualHost 10.1.2.3><br />
3510 <span class="indent">
3511 ServerAdmin webmaster@host.example.com<br />
3512 DocumentRoot /www/docs/host.example.com<br />
3513 ServerName host.example.com<br />
3514 ErrorLog logs/host.example.com-error_log<br />
3515 TransferLog logs/host.example.com-access_log<br />
3517 </VirtualHost>
3521 <p>IPv6 addresses must be specified in square brackets because
3522 the optional port number could not be determined otherwise. An
3523 IPv6 example is shown below:</p>
3525 <div class="example"><p><code>
3526 <VirtualHost [2001:db8::a00:20ff:fea7:ccea]><br />
3527 <span class="indent">
3528 ServerAdmin webmaster@host.example.com<br />
3529 DocumentRoot /www/docs/host.example.com<br />
3530 ServerName host.example.com<br />
3531 ErrorLog logs/host.example.com-error_log<br />
3532 TransferLog logs/host.example.com-access_log<br />
3534 </VirtualHost>
3537 <p>Each Virtual Host must correspond to a different IP address,
3538 different port number or a different host name for the server,
3539 in the former case the server machine must be configured to
3540 accept IP packets for multiple addresses. (If the machine does
3541 not have multiple network interfaces, then this can be
3542 accomplished with the <code>ifconfig alias</code> command -- if
3543 your OS supports it).</p>
3545 <div class="note"><h3>Note</h3>
3546 <p>The use of <code class="directive"><VirtualHost></code> does
3547 <strong>not</strong> affect what addresses Apache listens on. You
3548 may need to ensure that Apache is listening on the correct addresses
3549 using <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code>.</p>
3552 <p>When using IP-based virtual hosting, the special name
3553 <code>_default_</code> can be specified in
3554 which case this virtual host will match any IP address that is
3555 not explicitly listed in another virtual host. In the absence
3556 of any <code>_default_</code> virtual host the "main" server config,
3557 consisting of all those definitions outside any VirtualHost
3558 section, is used when no IP-match occurs.</p>
3560 <p>You can specify a <code>:port</code> to change the port that is
3561 matched. If unspecified then it defaults to the same port as the
3562 most recent <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code>
3563 statement of the main server. You may also specify <code>:*</code>
3564 to match all ports on that address. (This is recommended when used
3565 with <code>_default_</code>.)</p>
3567 <p>A <code class="directive"><a href="#servername">ServerName</a></code> should be
3568 specified inside each <code class="directive"><VirtualHost></code> block. If it is absent, the
3569 <code class="directive"><a href="#servername">ServerName</a></code> from the "main"
3570 server configuration will be inherited.</p>
3572 <div class="warning"><h3>Security</h3>
3573 <p>See the <a href="../misc/security_tips.html">security tips</a>
3574 document for details on why your security could be compromised if the
3575 directory where log files are stored is writable by anyone other
3576 than the user that starts the server.</p>
3581 <li><a href="../vhosts/">Apache Virtual Host documentation</a></li>
3582 <li><a href="../dns-caveats.html">Issues Regarding DNS and
3584 <li><a href="../bind.html">Setting
3585 which addresses and ports Apache uses</a></li>
3586 <li><a href="../sections.html">How <Directory>, <Location>
3587 and <Files> sections work</a> for an explanation of how these
3588 different sections are combined when a request is received</li>
3592 <div class="bottomlang">
3593 <p><span>Available Languages: </span><a href="../de/mod/core.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
3594 <a href="../en/mod/core.html" title="English"> en </a> |
3595 <a href="../fr/mod/core.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
3596 <a href="../ja/mod/core.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
3597 <a href="../tr/mod/core.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p>
3598 </div><div id="footer">
3599 <p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
3600 <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></div>