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7 Copyright 2002-2004 The Apache Software Foundation
9 Licensed under the Apache License, Version 2.0 (the "License");
10 you may not use this file except in compliance with the License.
11 You may obtain a copy of the License at
13 http://www.apache.org/licenses/LICENSE-2.0
15 Unless required by applicable law or agreed to in writing, software
16 distributed under the License is distributed on an "AS IS" BASIS,
17 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
18 See the License for the specific language governing permissions and
19 limitations under the License.
22 <modulesynopsis metafile="core.xml.meta">
25 <description>Core Apache HTTP Server features that are always
26 available</description>
30 <name>AcceptPathInfo</name>
31 <description>Resources accept trailing pathname information</description>
32 <syntax>AcceptPathInfo On|Off|Default</syntax>
33 <default>AcceptPathInfo Default</default>
34 <contextlist><context>server config</context>
35 <context>virtual host</context><context>directory</context>
36 <context>.htaccess</context></contextlist>
37 <override>FileInfo</override>
38 <compatibility>Available in Apache 2.0.30 and later</compatibility>
42 <p>This directive controls whether requests that contain trailing
43 pathname information that follows an actual filename (or
44 non-existent file in an existing directory) will be accepted or
45 rejected. The trailing pathname information can be made
46 available to scripts in the <code>PATH_INFO</code> environment
49 <p>For example, assume the location <code>/test/</code> points to
50 a directory that contains only the single file
51 <code>here.html</code>. Then requests for
52 <code>/test/here.html/more</code> and
53 <code>/test/nothere.html/more</code> both collect
54 <code>/more</code> as <code>PATH_INFO</code>.</p>
56 <p>The three possible arguments for the
57 <directive>AcceptPathInfo</directive> directive are:</p>
59 <dt><code>Off</code></dt><dd>A request will only be accepted if it
60 maps to a literal path that exists. Therefore a request with
61 trailing pathname information after the true filename such as
62 <code>/test/here.html/more</code> in the above example will return
63 a 404 NOT FOUND error.</dd>
65 <dt><code>On</code></dt><dd>A request will be accepted if a
66 leading path component maps to a file that exists. The above
67 example <code>/test/here.html/more</code> will be accepted if
68 <code>/test/here.html</code> maps to a valid file.</dd>
70 <dt><code>Default</code></dt><dd>The treatment of requests with
71 trailing pathname information is determined by the <a
72 href="../handler.html">handler</a> responsible for the request.
73 The core handler for normal files defaults to rejecting
74 <code>PATH_INFO</code> requests. Handlers that serve scripts, such as <a
75 href="mod_cgi.html">cgi-script</a> and <a
76 href="mod_isapi.html">isapi-isa</a>, generally accept
77 <code>PATH_INFO</code> by default.</dd>
80 <p>The primary purpose of the <code>AcceptPathInfo</code>
81 directive is to allow you to override the handler's choice of
82 accepting or rejecting <code>PATH_INFO</code>. This override is required,
83 for example, when you use a <a href="../filter.html">filter</a>, such
84 as <a href="mod_include.html">INCLUDES</a>, to generate content
85 based on <code>PATH_INFO</code>. The core handler would usually reject
86 the request, so you can use the following configuration to enable
90 <Files "mypaths.shtml"><br />
92 Options +Includes<br />
93 SetOutputFilter INCLUDES<br />
94 AcceptPathInfo On<br />
103 <name>AccessFileName</name>
104 <description>Name of the distributed configuration file</description>
105 <syntax>AccessFileName <var>filename</var> [<var>filename</var>] ...</syntax>
106 <default>AccessFileName .htaccess</default>
107 <contextlist><context>server config</context><context>virtual host</context>
111 <p>While processing a request the server looks for
112 the first existing configuration file from this list of names in
113 every directory of the path to the document, if distributed
114 configuration files are <a href="#allowoverride">enabled for that
115 directory</a>. For example:</p>
121 <p>before returning the document
122 <code>/usr/local/web/index.html</code>, the server will read
123 <code>/.acl</code>, <code>/usr/.acl</code>,
124 <code>/usr/local/.acl</code> and <code>/usr/local/web/.acl</code>
125 for directives, unless they have been disabled with</p>
128 <Directory /><br />
130 AllowOverride None<br />
135 <seealso><directive module="core">AllowOverride</directive></seealso>
136 <seealso><a href="../configuring.html">Configuration Files</a></seealso>
137 <seealso><a href="../howto/htaccess.html">.htaccess Files</a></seealso>
141 <name>AddDefaultCharset</name>
142 <description>Default character set to be added for a
143 response without an explicit character set</description>
144 <syntax>AddDefaultCharset On|Off|<var>charset</var></syntax>
145 <default>AddDefaultCharset Off</default>
146 <contextlist><context>server config</context>
147 <context>virtual host</context><context>directory</context>
148 <context>.htaccess</context></contextlist>
149 <override>FileInfo</override>
152 <p>This directive specifies the name of the character set that
153 will be added to any response that does not have any parameter on
154 the content type in the HTTP headers. This will override any
155 character set specified in the body of the document via a
156 <code>META</code> tag. A setting of <code>AddDefaultCharset
157 Off</code> disables this
158 functionality. <code>AddDefaultCharset On</code> enables
159 Apache's internal default charset of <code>iso-8859-1</code> as
160 required by the directive. You can also specify an alternate
161 <var>charset</var> to be used. For example:</p>
164 AddDefaultCharset utf-8
170 <name>AddOutputFilterByType</name>
171 <description>assigns an output filter to a particular MIME-type</description>
172 <syntax>AddOutputFilterByType <var>filter</var>[;<var>filter</var>...]
173 <var>MIME-type</var> [<var>MIME-type</var>] ...</syntax>
174 <contextlist><context>server config</context>
175 <context>virtual host</context><context>directory</context>
176 <context>.htaccess</context></contextlist>
177 <override>FileInfo</override>
178 <compatibility>Available in Apache 2.0.33 and later</compatibility>
181 <p>This directive activates a particular output <a
182 href="../filter.html">filter</a> for a request depending on the
183 response MIME-type.</p>
185 <p>The following example uses the <code>DEFLATE</code> filter, which
186 is provided by <module>mod_deflate</module>. It will compress all
187 output (either static or dynamic) which is labeled as
188 <code>text/html</code> or <code>text/plain</code> before it is sent
192 AddOutputFilterByType DEFLATE text/html text/plain
195 <p>If you want the content to be processed by more than one filter, their
196 names have to be separated by semicolons. It's also possible to use one
197 <directive>AddOutputFilterByType</directive> directive for each of
200 <p>The configuration below causes all script output labeled as
201 <code>text/html</code> to be processed at first by the
202 <code>INCLUDES</code> filter and then by the <code>DEFLATE</code>
206 <Location /cgi-bin/><br />
208 Options Includes<br />
209 AddOutputFilterByType INCLUDES;DEFLATE text/html<br />
214 <note type="warning"><title>Note</title>
215 <p>Enabling filters with <directive>AddOutputFilterByType</directive>
216 may fail partially or completely in some cases. For example, no
217 filters are applied if the MIME-type could not be determined and falls
218 back to the <directive module="core">DefaultType</directive> setting,
219 even if the <directive module="core">DefaultType</directive> is the
222 <p>However, if you want to make sure, that the filters will be
223 applied, assign the content type to a resource explicitly, for
224 example with <directive module="mod_mime">AddType</directive> or
225 <directive module="core">ForceType</directive>. Setting the
226 content type within a (non-nph) CGI script is also safe.</p>
228 <p>The by-type output filters are never applied on proxy requests.</p>
232 <seealso><directive module="mod_mime">AddOutputFilter</directive></seealso>
233 <seealso><directive module="core">SetOutputFilter</directive></seealso>
234 <seealso><a href="../filter.html">filters</a></seealso>
238 <name>AllowEncodedSlashes</name>
239 <description>Determines whether encoded path separators in URLs are allowed to
240 be passed through</description>
241 <syntax>AllowEncodedSlashes On|Off</syntax>
242 <default>AllowEncodedSlashes Off</default>
243 <contextlist><context>server config</context><context>virtual host</context>
245 <compatibility>Available in Apache 2.0.46 and later</compatibility>
248 <p>The <directive>AllowEncodedSlashes</directive> directive allows URLs
249 which contain encoded path separators (<code>%2F</code> for <code>/</code>
250 and additionally <code>%5C</code> for <code>\</code> on according systems)
251 to be used. Normally such URLs are refused with a 404 (Not found) error.</p>
253 <p>Turning <directive>AllowEncodedSlashes</directive> <code>On</code> is
254 mostly useful when used in conjunction with <code>PATH_INFO</code>.</p>
256 <note><title>Note</title>
257 <p>Allowing encoded slashes does <em>not</em> imply <em>decoding</em>.
258 Occurrences of <code>%2F</code> or <code>%5C</code> (<em>only</em> on
259 according systems) will be left as such in the otherwise decoded URL
263 <seealso><directive module="core">AcceptPathInfo</directive></seealso>
267 <name>AllowOverride</name>
268 <description>Types of directives that are allowed in
269 <code>.htaccess</code> files</description>
270 <syntax>AllowOverride All|None|<var>directive-type</var>
271 [<var>directive-type</var>] ...</syntax>
272 <default>AllowOverride All</default>
273 <contextlist><context>directory</context></contextlist>
276 <p>When the server finds an <code>.htaccess</code> file (as
277 specified by <directive module="core">AccessFileName</directive>)
278 it needs to know which directives declared in that file can override
279 earlier configuration directives.</p>
281 <note><title>Only available in <Directory> sections</title>
282 <directive>AllowOverride</directive> is valid only in
283 <directive type="section" module="core">Directory</directive>
284 sections specified without regular expressions, not in <directive
285 type="section" module="core">Location</directive>, <directive
286 module="core" type="section">DirectoryMatch</directive> or
287 <directive type="section" module="core">Files</directive> sections.
290 <p>When this directive is set to <code>None</code>, then
291 <a href="#accessfilename">.htaccess</a> files are completely ignored.
292 In this case, the server will not even attempt to read
293 <code>.htaccess</code> files in the filesystem.</p>
295 <p>When this directive is set to <code>All</code>, then any
296 directive which has the .htaccess <a
297 href="directive-dict.html#Context">Context</a> is allowed in
298 <code>.htaccess</code> files.</p>
300 <p>The <var>directive-type</var> can be one of the following
301 groupings of directives.</p>
308 Allow use of the authorization directives (<directive
309 module="mod_authn_dbm">AuthDBMGroupFile</directive>,
310 <directive module="mod_authn_dbm">AuthDBMUserFile</directive>,
311 <directive module="mod_authz_groupfile">AuthGroupFile</directive>,
312 <directive module="core">AuthName</directive>,
313 <directive module="core">AuthType</directive>, <directive
314 module="mod_authn_file">AuthUserFile</directive>, <directive
315 module="core">Require</directive>, <em>etc.</em>).</dd>
320 Allow use of the directives controlling document types (<directive
321 module="core">DefaultType</directive>, <directive
322 module="core">ErrorDocument</directive>, <directive
323 module="core">ForceType</directive>, <directive
324 module="mod_negotiation">LanguagePriority</directive>,
325 <directive module="core">SetHandler</directive>, <directive
326 module="core">SetInputFilter</directive>, <directive
327 module="core">SetOutputFilter</directive>, and
328 <module>mod_mime</module> Add* and Remove*
329 directives, <em>etc.</em>).</dd>
334 Allow use of the directives controlling directory indexing
336 module="mod_autoindex">AddDescription</directive>,
337 <directive module="mod_autoindex">AddIcon</directive>, <directive
338 module="mod_autoindex">AddIconByEncoding</directive>,
339 <directive module="mod_autoindex">AddIconByType</directive>,
340 <directive module="mod_autoindex">DefaultIcon</directive>, <directive
341 module="mod_dir">DirectoryIndex</directive>, <directive
342 module="mod_autoindex">FancyIndexing</directive>, <directive
343 module="mod_autoindex">HeaderName</directive>, <directive
344 module="mod_autoindex">IndexIgnore</directive>, <directive
345 module="mod_autoindex">IndexOptions</directive>, <directive
346 module="mod_autoindex">ReadmeName</directive>,
352 Allow use of the directives controlling host access (<directive
353 module="mod_authz_host">Allow</directive>, <directive
354 module="mod_authz_host">Deny</directive> and <directive
355 module="mod_authz_host">Order</directive>).</dd>
357 <dt>Options[=<var>Option</var>,...]</dt>
360 Allow use of the directives controlling specific directory
361 features (<directive module="core">Options</directive> and
362 <directive module="mod_include">XBitHack</directive>).
363 An equal sign may be given followed by a comma (but no spaces)
364 separated lists of options that may be set using the <directive
365 module="core">Options</directive> command.</dd>
371 AllowOverride AuthConfig Indexes
374 <p>In the example above all directives that are neither in the group
375 <code>AuthConfig</code> nor <code>Indexes</code> cause an internal
379 <seealso><directive module="core">AccessFileName</directive></seealso>
380 <seealso><a href="../configuring.html">Configuration Files</a></seealso>
381 <seealso><a href="../howto/htaccess.html">.htaccess Files</a></seealso>
385 <name>AuthName</name>
386 <description>Authorization realm for use in HTTP
387 authentication</description>
388 <syntax>AuthName <var>auth-domain</var></syntax>
389 <contextlist><context>directory</context><context>.htaccess</context>
391 <override>AuthConfig</override>
394 <p>This directive sets the name of the authorization realm for a
395 directory. This realm is given to the client so that the user
396 knows which username and password to send.
397 <directive>AuthName</directive> takes a single argument; if the
398 realm name contains spaces, it must be enclosed in quotation
399 marks. It must be accompanied by <directive
400 module="core">AuthType</directive> and <directive
401 module="core">Require</directive> directives, and directives such
402 as <directive module="mod_authn_file">AuthUserFile</directive> and
403 <directive module="mod_authz_groupfile">AuthGroupFile</directive> to
409 AuthName "Top Secret"
412 <p>The string provided for the <code>AuthName</code> is what will
413 appear in the password dialog provided by most browsers.</p>
416 href="../howto/auth.html">Authentication, Authorization, and
417 Access Control</a></seealso>
421 <name>AuthType</name>
422 <description>Type of user authentication</description>
423 <syntax>AuthType Basic|Digest</syntax>
424 <contextlist><context>directory</context><context>.htaccess</context>
426 <override>AuthConfig</override>
429 <p>This directive selects the type of user authentication for a
430 directory. Only <code>Basic</code> and <code>Digest</code> are
431 currently implemented.
433 It must be accompanied by <directive
434 module="core">AuthName</directive> and <directive
435 module="core">Require</directive> directives, and directives such
436 as <directive module="mod_authn_file">AuthUserFile</directive> and
437 <directive module="mod_authz_groupfile">AuthGroupFile</directive> to
440 <seealso><a href="../howto/auth.html">Authentication, Authorization,
441 and Access Control</a></seealso>
445 <name>CGIMapExtension</name>
446 <description>Technique for locating the interpreter for CGI
447 scripts</description>
448 <syntax>CGIMapExtension <var>cgi-path</var> <var>.extension</var></syntax>
449 <contextlist><context>directory</context><context>.htaccess</context>
451 <override>FileInfo</override>
452 <compatibility>NetWare only</compatibility>
455 <p>This directive is used to control how Apache finds the
456 interpreter used to run CGI scripts. For example, setting
457 <code>CGIMapExtension sys:\foo.nlm .foo</code> will
458 cause all CGI script files with a <code>.foo</code> extension to
459 be passed to the FOO interpreter.</p>
464 <name>ContentDigest</name>
465 <description>Enables the generation of <code>Content-MD5</code> HTTP Response
466 headers</description>
467 <syntax>ContentDigest On|Off</syntax>
468 <default>ContentDigest Off</default>
469 <contextlist><context>server config</context><context>virtual host</context>
470 <context>directory</context><context>.htaccess</context>
472 <override>Options</override>
473 <status>Experimental</status>
476 <p>This directive enables the generation of
477 <code>Content-MD5</code> headers as defined in RFC1864
478 respectively RFC2068.</p>
480 <p>MD5 is an algorithm for computing a "message digest"
481 (sometimes called "fingerprint") of arbitrary-length data, with
482 a high degree of confidence that any alterations in the data
483 will be reflected in alterations in the message digest.</p>
485 <p>The <code>Content-MD5</code> header provides an end-to-end
486 message integrity check (MIC) of the entity-body. A proxy or
487 client may check this header for detecting accidental
488 modification of the entity-body in transit. Example header:</p>
491 Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==
494 <p>Note that this can cause performance problems on your server
495 since the message digest is computed on every request (the
496 values are not cached).</p>
498 <p><code>Content-MD5</code> is only sent for documents served
499 by the <module>core</module>, and not by any module. For example,
500 SSI documents, output from CGI scripts, and byte range responses
501 do not have this header.</p>
506 <name>DefaultType</name>
507 <description>MIME content-type that will be sent if the
508 server cannot determine a type in any other way</description>
509 <syntax>DefaultType <var>MIME-type</var></syntax>
510 <default>DefaultType text/plain</default>
511 <contextlist><context>server config</context><context>virtual host</context>
512 <context>directory</context><context>.htaccess</context>
514 <override>FileInfo</override>
517 <p>There will be times when the server is asked to provide a
518 document whose type cannot be determined by its MIME types
521 <p>The server must inform the client of the content-type of the
522 document, so in the event of an unknown type it uses the
523 <code>DefaultType</code>. For example:</p>
526 DefaultType image/gif
529 <p>would be appropriate for a directory which contained many GIF
530 images with filenames missing the <code>.gif</code> extension.</p>
532 <p>Note that unlike <directive
533 module="core">ForceType</directive>, this directive only
534 provides the default mime-type. All other mime-type definitions,
535 including filename extensions, that might identify the media type
536 will override this default.</p>
540 <directivesynopsis type="section">
541 <name>Directory</name>
542 <description>Enclose a group of directives that apply only to the
543 named file-system directory and sub-directories</description>
544 <syntax><Directory <var>directory-path</var>>
545 ... </Directory></syntax>
546 <contextlist><context>server config</context><context>virtual host</context>
550 <p><directive type="section">Directory</directive> and
551 <code></Directory></code> are used to enclose a group of
552 directives that will apply only to the named directory and
553 sub-directories of that directory. Any directive that is allowed
554 in a directory context may be used. <var>Directory-path</var> is
555 either the full path to a directory, or a wild-card string using
556 Unix shell-style matching. In a wild-card string, <code>?</code> matches
557 any single character, and <code>*</code> matches any sequences of
558 characters. You may also use <code>[]</code> character ranges. None
559 of the wildcards match a `/' character, so <code><Directory
560 /*/public_html></code> will not match
561 <code>/home/user/public_html</code>, but <code><Directory
562 /home/*/public_html></code> will match. Example:</p>
565 <Directory /usr/local/httpd/htdocs><br />
567 Options Indexes FollowSymLinks<br />
573 <p>Be careful with the <var>directory-path</var> arguments:
574 They have to literally match the filesystem path which Apache uses
575 to access the files. Directives applied to a particular
576 <code><Directory></code> will not apply to files accessed from
577 that same directory via a different path, such as via different symbolic
582 expressions can also be used, with the addition of the
583 <code>~</code> character. For example:</p>
586 <Directory ~ "^/www/.*/[0-9]{3}">
589 <p>would match directories in <code>/www/</code> that consisted of
592 <p>If multiple (non-regular expression) <directive
593 type="section">Directory</directive> sections
594 match the directory (or one of its parents) containing a document,
595 then the directives are applied in the order of shortest match
596 first, interspersed with the directives from the <a
597 href="#accessfilename">.htaccess</a> files. For example,
601 <Directory /><br />
603 AllowOverride None<br />
605 </Directory><br />
607 <Directory /home/><br />
609 AllowOverride FileInfo<br />
614 <p>for access to the document <code>/home/web/dir/doc.html</code>
618 <li>Apply directive <code>AllowOverride None</code>
619 (disabling <code>.htaccess</code> files).</li>
621 <li>Apply directive <code>AllowOverride FileInfo</code> (for
622 directory <code>/home</code>).</li>
624 <li>Apply any <code>FileInfo</code> directives in
625 <code>/home/.htaccess</code>, <code>/home/web/.htaccess</code> and
626 <code>/home/web/dir/.htaccess</code> in that order.</li>
629 <p>Regular expressions are not considered until after all of the
630 normal sections have been applied. Then all of the regular
631 expressions are tested in the order they appeared in the
632 configuration file. For example, with</p>
635 <Directory ~ abc$><br />
637 # ... directives here ...<br />
642 <p>the regular expression section won't be considered until after
643 all normal <directive type="section">Directory</directive>s and
644 <code>.htaccess</code> files have been applied. Then the regular
645 expression will match on <code>/home/abc/public_html/abc</code> and
646 the corresponding <directive type="section">Directory</directive> will
649 <p><strong>Note that the default Apache access for
650 <code><Directory /></code> is <code>Allow from All</code>.
651 This means that Apache will serve any file mapped from an URL. It is
652 recommended that you change this with a block such
656 <Directory /><br />
658 Order Deny,Allow<br />
664 <p><strong>and then override this for directories you
665 <em>want</em> accessible. See the <a
666 href="../misc/security_tips.html">Security Tips</a> page for more
667 details.</strong></p>
669 <p>The directory sections occur in the <code>httpd.conf</code> file.
670 <directive type="section">Directory</directive> directives
671 cannot nest, and cannot appear in a <directive module="core"
672 type="section">Limit</directive> or <directive module="core"
673 type="section">LimitExcept</directive> section.</p>
675 <seealso><a href="../sections.html">How <Directory>,
676 <Location> and <Files> sections work</a> for an
677 explanation of how these different sections are combined when a
678 request is received</seealso>
681 <directivesynopsis type="section">
682 <name>DirectoryMatch</name>
683 <description>Enclose directives that apply to
684 file-system directories matching a regular expression and their
685 subdirectories</description>
686 <syntax><DirectoryMatch <var>regex</var>>
687 ... </DirectoryMatch></syntax>
688 <contextlist><context>server config</context><context>virtual host</context>
692 <p><directive type="section">DirectoryMatch</directive> and
693 <code></DirectoryMatch></code> are used to enclose a group
694 of directives which will apply only to the named directory and
695 sub-directories of that directory, the same as <directive
696 module="core" type="section">Directory</directive>. However, it
697 takes as an argument a regular expression. For example:</p>
700 <DirectoryMatch "^/www/.*/[0-9]{3}">
703 <p>would match directories in <code>/www/</code> that consisted of three
706 <seealso><directive type="section" module="core">Directory</directive> for
707 a description of how regular expressions are mixed in with normal
708 <directive type="section">Directory</directive>s</seealso>
710 href="../sections.html">How <Directory>, <Location> and
711 <Files> sections work</a> for an explanation of how these different
712 sections are combined when a request is received</seealso>
716 <name>DocumentRoot</name>
717 <description>Directory that forms the main document tree visible
718 from the web</description>
719 <syntax>DocumentRoot <var>directory-path</var></syntax>
720 <default>DocumentRoot /usr/local/apache/htdocs</default>
721 <contextlist><context>server config</context><context>virtual host</context>
725 <p>This directive sets the directory from which <program>httpd</program>
726 will serve files. Unless matched by a directive like <directive
727 module="mod_alias">Alias</directive>, the server appends the
728 path from the requested URL to the document root to make the
729 path to the document. Example:</p>
732 DocumentRoot /usr/web
736 <code>http://www.my.host.com/index.html</code> refers to
737 <code>/usr/web/index.html</code>. If the <var>directory-path</var> is
738 not absolute then it is assumed to be relative to the <directive
739 module="core">ServerRoot</directive>.</p>
741 <p>The <directive>DocumentRoot</directive> should be specified without
742 a trailing slash.</p>
744 <seealso><a href="../urlmapping.html">Mapping URLs to Filesystem
745 Location</a></seealso>
749 <name>EnableMMAP</name>
750 <description>Use memory-mapping to read files during delivery</description>
751 <syntax>EnableMMAP On|Off</syntax>
752 <default>EnableMMAP On</default>
753 <contextlist><context>server config</context><context>virtual host</context>
754 <context>directory</context><context>.htaccess</context>
756 <override>FileInfo</override>
759 <p>This directive controls whether the <program>httpd</program> may use
760 memory-mapping if it needs to read the contents of a file during
761 delivery. By default, when the handling of a request requires
762 access to the data within a file -- for example, when delivering a
763 server-parsed file using <module>mod_include</module> -- Apache
764 memory-maps the file if the OS supports it.</p>
766 <p>This memory-mapping sometimes yields a performance improvement.
767 But in some environments, it is better to disable the memory-mapping
768 to prevent operational problems:</p>
771 <li>On some multiprocessor systems, memory-mapping can reduce the
772 performance of the <program>httpd</program>.</li>
773 <li>With an NFS-mounted <directive module="core">DocumentRoot</directive>,
774 the <program>httpd</program> may crash due to a segmentation fault if a file
775 is deleted or truncated while the <program>httpd</program> has it
779 <p>For server configurations that are vulnerable to these problems,
780 you should disable memory-mapping of delivered files by specifying:</p>
786 <p>For NFS mounted files, this feature may be disabled explicitly for
787 the offending files by specifying:</p>
790 <Directory "/path-to-nfs-files">
800 <name>EnableSendfile</name>
801 <description>Use the kernel sendfile support to deliver files to the client</description>
802 <syntax>EnableSendfile On|Off</syntax>
803 <default>EnableSendfile On</default>
804 <contextlist><context>server config</context><context>virtual host</context>
805 <context>directory</context><context>.htaccess</context>
807 <override>FileInfo</override>
808 <compatibility>Available in version 2.0.44 and later</compatibility>
811 <p>This directive controls whether <program>httpd</program> may use the
812 sendfile support from the kernel to transmit file contents to the client.
813 By default, when the handling of a request requires no access
814 to the data within a file -- for example, when delivering a
815 static file -- Apache uses sendfile to deliver the file contents
816 without ever reading the file if the OS supports it.</p>
818 <p>This sendfile mechanism avoids separate read and send operations,
819 and buffer allocations. But on some platforms or within some
820 filesystems, it is better to disable this feature to avoid
821 operational problems:</p>
824 <li>Some platforms may have broken sendfile support that the build
825 system did not detect, especially if the binaries were built on
826 another box and moved to such a machine with broken sendfile
828 <li>On Linux the use of sendfile triggers TCP-checksum
829 offloading bugs on certain networking cards when using IPv6.</li>
830 <li>With a network-mounted <directive
831 module="core">DocumentRoot</directive> (e.g., NFS or SMB),
832 the kernel may be unable to serve the network file through
836 <p>For server configurations that are vulnerable to these problems,
837 you should disable this feature by specifying:</p>
843 <p>For NFS or SMB mounted files, this feature may be disabled explicitly
844 for the offending files by specifying:</p>
847 <Directory "/path-to-nfs-files">
857 <name>ErrorDocument</name>
858 <description>What the server will return to the client
859 in case of an error</description>
860 <syntax>ErrorDocument <var>error-code</var> <var>document</var></syntax>
861 <contextlist><context>server config</context><context>virtual host</context>
862 <context>directory</context><context>.htaccess</context>
864 <override>FileInfo</override>
865 <compatibility>Quoting syntax for text messages is different in Apache
869 <p>In the event of a problem or error, Apache can be configured
870 to do one of four things,</p>
873 <li>output a simple hardcoded error message</li>
875 <li>output a customized message</li>
877 <li>redirect to a local <var>URL-path</var> to handle the
880 <li>redirect to an external <var>URL</var> to handle the
884 <p>The first option is the default, while options 2-4 are
885 configured using the <directive>ErrorDocument</directive>
886 directive, which is followed by the HTTP response code and a URL
887 or a message. Apache will sometimes offer additional information
888 regarding the problem/error.</p>
890 <p>URLs can begin with a slash (/) for local URLs, or be a full
891 URL which the client can resolve. Alternatively, a message can
892 be provided to be displayed by the browser. Examples:</p>
895 ErrorDocument 500 http://foo.example.com/cgi-bin/tester<br />
896 ErrorDocument 404 /cgi-bin/bad_urls.pl<br />
897 ErrorDocument 401 /subscription_info.html<br />
898 ErrorDocument 403 "Sorry can't allow you access today"
901 <p>Additionally, the special value <code>default</code> can be used
902 to specify Apache's simple hardcoded message. While not required
903 under normal circumstances, <code>default</code> will restore
904 Apache's simple hardcoded message for configurations that would
905 otherwise inherit an existing <directive>ErrorDocument</directive>.</p>
908 ErrorDocument 404 /cgi-bin/bad_urls.pl<br /><br />
909 <Directory /web/docs><br />
911 ErrorDocument 404 default<br />
916 <p>Note that when you specify an <directive>ErrorDocument</directive>
917 that points to a remote URL (ie. anything with a method such as
918 <code>http</code> in front of it), Apache will send a redirect to the
919 client to tell it where to find the document, even if the
920 document ends up being on the same server. This has several
921 implications, the most important being that the client will not
922 receive the original error status code, but instead will
923 receive a redirect status code. This in turn can confuse web
924 robots and other clients which try to determine if a URL is
925 valid using the status code. In addition, if you use a remote
926 URL in an <code>ErrorDocument 401</code>, the client will not
927 know to prompt the user for a password since it will not
928 receive the 401 status code. Therefore, <strong>if you use an
929 <code>ErrorDocument 401</code> directive then it must refer to a local
930 document.</strong></p>
932 <p>Microsoft Internet Explorer (MSIE) will by default ignore
933 server-generated error messages when they are "too small" and substitute
934 its own "friendly" error messages. The size threshold varies depending on
935 the type of error, but in general, if you make your error document
936 greater than 512 bytes, then MSIE will show the server-generated
937 error rather than masking it. More information is available in
938 Microsoft Knowledge Base article <a
939 href="http://support.microsoft.com/default.aspx?scid=kb;en-us;Q294807"
942 <p>Prior to version 2.0, messages were indicated by prefixing
943 them with a single unmatched double quote character.</p>
946 <seealso><a href="../custom-error.html">documentation of
947 customizable responses</a></seealso>
951 <name>ErrorLog</name>
952 <description>Location where the server will log errors</description>
953 <syntax> ErrorLog <var>file-path</var>|syslog[:<var>facility</var>]</syntax>
954 <default>ErrorLog logs/error_log (Unix) ErrorLog logs/error.log (Windows and OS/2)</default>
955 <contextlist><context>server config</context><context>virtual host</context>
959 <p>The <directive>ErrorLog</directive> directive sets the name of
960 the file to which the server will log any errors it encounters. If
961 the <var>file-path</var> is not absolute then it is assumed to be
962 relative to the <directive module="core">ServerRoot</directive>.</p>
964 <example><title>Example</title>
965 ErrorLog /var/log/httpd/error_log
968 <p>If the <var>file-path</var>
969 begins with a pipe (|) then it is assumed to be a command to spawn
970 to handle the error log.</p>
972 <example><title>Example</title>
973 ErrorLog "|/usr/local/bin/httpd_errors"
976 <p>Using <code>syslog</code> instead of a filename enables logging
977 via syslogd(8) if the system supports it. The default is to use
978 syslog facility <code>local7</code>, but you can override this by
979 using the <code>syslog:<var>facility</var></code> syntax where
980 <var>facility</var> can be one of the names usually documented in
983 <example><title>Example</title>
987 <p>SECURITY: See the <a
988 href="../misc/security_tips.html#serverroot">security tips</a>
989 document for details on why your security could be compromised
990 if the directory where log files are stored is writable by
991 anyone other than the user that starts the server.</p>
992 <note type="warning"><title>Note</title>
993 <p>When entering a file path on non-Unix platforms, care should be taken
994 to make sure that only forward slashed are used even though the platform
995 may allow the use of back slashes. In general it is a good idea to always
996 use forward slashes throughout the configuration files.</p>
999 <seealso><directive module="core">LogLevel</directive></seealso>
1000 <seealso><a href="../logs.html">Apache Log Files</a></seealso>
1001 </directivesynopsis>
1004 <name>FileETag</name>
1005 <description>File attributes used to create the ETag
1006 HTTP response header</description>
1007 <syntax>FileETag <var>component</var> ...</syntax>
1008 <default>FileETag INode MTime Size</default>
1009 <contextlist><context>server config</context><context>virtual host</context>
1010 <context>directory</context><context>.htaccess</context>
1012 <override>FileInfo</override>
1016 The <directive>FileETag</directive> directive configures the file
1017 attributes that are used to create the <code>ETag</code> (entity
1018 tag) response header field when the document is based on a file.
1019 (The <code>ETag</code> value is used in cache management to save
1020 network bandwidth.) In Apache 1.3.22 and earlier, the
1021 <code>ETag</code> value was <em>always</em> formed
1022 from the file's inode, size, and last-modified time (mtime). The
1023 <directive>FileETag</directive> directive allows you to choose
1024 which of these -- if any -- should be used. The recognized keywords are:
1028 <dt><strong>INode</strong></dt>
1029 <dd>The file's i-node number will be included in the calculation</dd>
1030 <dt><strong>MTime</strong></dt>
1031 <dd>The date and time the file was last modified will be included</dd>
1032 <dt><strong>Size</strong></dt>
1033 <dd>The number of bytes in the file will be included</dd>
1034 <dt><strong>All</strong></dt>
1035 <dd>All available fields will be used. This is equivalent to:
1036 <example>FileETag INode MTime Size</example></dd>
1037 <dt><strong>None</strong></dt>
1038 <dd>If a document is file-based, no <code>ETag</code> field will be
1039 included in the response</dd>
1042 <p>The <code>INode</code>, <code>MTime</code>, and <code>Size</code>
1043 keywords may be prefixed with either <code>+</code> or <code>-</code>,
1044 which allow changes to be made to the default setting inherited
1045 from a broader scope. Any keyword appearing without such a prefix
1046 immediately and completely cancels the inherited setting.</p>
1048 <p>If a directory's configuration includes
1049 <code>FileETag INode MTime Size</code>, and a
1050 subdirectory's includes <code>FileETag -INode</code>,
1051 the setting for that subdirectory (which will be inherited by
1052 any sub-subdirectories that don't override it) will be equivalent to
1053 <code>FileETag MTime Size</code>.</p>
1055 </directivesynopsis>
1057 <directivesynopsis type="section">
1059 <description>Contains directives that apply to matched
1060 filenames</description>
1061 <syntax><Files <var>filename</var>> ... </Files></syntax>
1062 <contextlist><context>server config</context><context>virtual host</context>
1063 <context>directory</context><context>.htaccess</context>
1065 <override>All</override>
1068 <p>The <directive type="section">Files</directive> directive
1069 limits the scope of the enclosed directives by filename. It is comparable
1070 to the <directive module="core" type="section">Directory</directive>
1071 and <directive module="core" type="section">Location</directive>
1072 directives. It should be matched with a <code></Files></code>
1073 directive. The directives given within this section will be applied to
1074 any object with a basename (last component of filename) matching the
1075 specified filename. <directive type="section">Files</directive>
1076 sections are processed in the order they appear in the
1077 configuration file, after the <directive module="core"
1078 type="section">Directory</directive> sections and
1079 <code>.htaccess</code> files are read, but before <directive
1080 type="section" module="core">Location</directive> sections. Note
1081 that <directive type="section">Files</directive> can be nested
1082 inside <directive type="section"
1083 module="core">Directory</directive> sections to restrict the
1084 portion of the filesystem they apply to.</p>
1086 <p>The <var>filename</var> argument should include a filename, or
1087 a wild-card string, where <code>?</code> matches any single character,
1088 and <code>*</code> matches any sequences of characters. Extended regular
1089 expressions can also be used, with the addition of the
1090 <code>~</code> character. For example:</p>
1093 <Files ~ "\.(gif|jpe?g|png)$">
1096 <p>would match most common Internet graphics formats. <directive
1097 module="core" type="section">FilesMatch</directive> is preferred,
1100 <p>Note that unlike <directive type="section"
1101 module="core">Directory</directive> and <directive type="section"
1102 module="core">Location</directive> sections, <directive
1103 type="section">Files</directive> sections can be used inside
1104 <code>.htaccess</code> files. This allows users to control access to
1105 their own files, at a file-by-file level.</p>
1108 <seealso><a href="../sections.html">How <Directory>, <Location>
1109 and <Files> sections work</a> for an explanation of how these
1110 different sections are combined when a request is received</seealso>
1111 </directivesynopsis>
1113 <directivesynopsis type="section">
1114 <name>FilesMatch</name>
1115 <description>Contains directives that apply to regular-expression matched
1116 filenames</description>
1117 <syntax><FilesMatch <var>regex</var>> ... </FilesMatch></syntax>
1118 <contextlist><context>server config</context><context>virtual host</context>
1119 <context>directory</context><context>.htaccess</context>
1121 <override>All</override>
1124 <p>The <directive type="section">FilesMatch</directive> directive
1125 limits the scope of the enclosed directives by filename, just as the
1126 <directive module="core" type="section">Files</directive> directive
1127 does. However, it accepts a regular expression. For example:</p>
1130 <FilesMatch "\.(gif|jpe?g|png)$">
1133 <p>would match most common Internet graphics formats.</p>
1136 <seealso><a href="../sections.html">How <Directory>, <Location>
1137 and <Files> sections work</a> for an explanation of how these
1138 different sections are combined when a request is received</seealso>
1139 </directivesynopsis>
1142 <name>ForceType</name>
1143 <description>Forces all matching files to be served with the specified
1144 MIME content-type</description>
1145 <syntax>ForceType <var>MIME-type</var>|None</syntax>
1146 <contextlist><context>directory</context><context>.htaccess</context>
1148 <override>FileInfo</override>
1149 <compatibility>Moved to the core in Apache 2.0</compatibility>
1152 <p>When placed into an <code>.htaccess</code> file or a
1153 <directive type="section" module="core">Directory</directive>, or
1154 <directive type="section" module="core">Location</directive> or
1155 <directive type="section" module="core">Files</directive>
1156 section, this directive forces all matching files to be served
1157 with the content type identification given by
1158 <var>MIME-type</var>. For example, if you had a directory full of
1159 GIF files, but did not want to label them all with <code>.gif</code>,
1160 you might want to use:</p>
1166 <p>Note that unlike <directive module="core">DefaultType</directive>,
1167 this directive overrides all mime-type associations, including
1168 filename extensions, that might identify the media type.</p>
1170 <p>You can override any <directive>ForceType</directive> setting
1171 by using the value of <code>None</code>:</p>
1174 # force all files to be image/gif:<br />
1175 <Location /images><br />
1177 ForceType image/gif<br />
1179 </Location><br />
1181 # but normal mime-type associations here:<br />
1182 <Location /images/mixed><br />
1184 ForceType None<br />
1189 </directivesynopsis>
1192 <name>HostnameLookups</name>
1193 <description>Enables DNS lookups on client IP addresses</description>
1194 <syntax>HostnameLookups On|Off|Double</syntax>
1195 <default>HostnameLookups Off</default>
1196 <contextlist><context>server config</context><context>virtual host</context>
1197 <context>directory</context></contextlist>
1200 <p>This directive enables DNS lookups so that host names can be
1201 logged (and passed to CGIs/SSIs in <code>REMOTE_HOST</code>).
1202 The value <code>Double</code> refers to doing double-reverse
1203 DNS lookup. That is, after a reverse lookup is performed, a forward
1204 lookup is then performed on that result. At least one of the IP
1205 addresses in the forward lookup must match the original
1206 address. (In "tcpwrappers" terminology this is called
1207 <code>PARANOID</code>.)</p>
1209 <p>Regardless of the setting, when <module>mod_authz_host</module> is
1210 used for controlling access by hostname, a double reverse lookup
1211 will be performed. This is necessary for security. Note that the
1212 result of this double-reverse isn't generally available unless you
1213 set <code>HostnameLookups Double</code>. For example, if only
1214 <code>HostnameLookups On</code> and a request is made to an object
1215 that is protected by hostname restrictions, regardless of whether
1216 the double-reverse fails or not, CGIs will still be passed the
1217 single-reverse result in <code>REMOTE_HOST</code>.</p>
1219 <p>The default is <code>Off</code> in order to save the network
1220 traffic for those sites that don't truly need the reverse
1221 lookups done. It is also better for the end users because they
1222 don't have to suffer the extra latency that a lookup entails.
1223 Heavily loaded sites should leave this directive
1224 <code>Off</code>, since DNS lookups can take considerable
1225 amounts of time. The utility <program>logresolve</program>, compiled by
1226 default to the <code>bin</code> subdirectory of your installation
1227 directory, can be used to look up host names from logged IP addresses
1230 </directivesynopsis>
1232 <directivesynopsis type="section">
1233 <name>IfDefine</name>
1234 <description>Encloses directives that will be processed only
1235 if a test is true at startup</description>
1236 <syntax><IfDefine [!]<var>parameter-name</var>> ...
1237 </IfDefine></syntax>
1238 <contextlist><context>server config</context><context>virtual host</context>
1239 <context>directory</context><context>.htaccess</context>
1241 <override>All</override>
1244 <p>The <code><IfDefine <var>test</var>>...</IfDefine>
1245 </code> section is used to mark directives that are conditional. The
1246 directives within an <directive type="section">IfDefine</directive>
1247 section are only processed if the <var>test</var> is true. If <var>
1248 test</var> is false, everything between the start and end markers is
1251 <p>The <var>test</var> in the <directive type="section"
1252 >IfDefine</directive> section directive can be one of two forms:</p>
1255 <li><var>parameter-name</var></li>
1257 <li><code>!</code><var>parameter-name</var></li>
1260 <p>In the former case, the directives between the start and end
1261 markers are only processed if the parameter named
1262 <var>parameter-name</var> is defined. The second format reverses
1263 the test, and only processes the directives if
1264 <var>parameter-name</var> is <strong>not</strong> defined.</p>
1266 <p>The <var>parameter-name</var> argument is a define as given on
1267 the <program>httpd</program> command line via <code>-D<var>parameter-</var>
1268 </code>, at the time the server was started.</p>
1270 <p><directive type="section">IfDefine</directive> sections are
1271 nest-able, which can be used to implement simple
1272 multiple-parameter tests. Example:</p>
1275 httpd -DReverseProxy ...<br />
1278 <IfDefine ReverseProxy><br />
1280 LoadModule rewrite_module modules/mod_rewrite.so<br />
1281 LoadModule proxy_module modules/libproxy.so<br />
1286 </directivesynopsis>
1288 <directivesynopsis type="section">
1289 <name>IfModule</name>
1290 <description>Encloses directives that are processed conditional on the
1291 presence or absence of a specific module</description>
1292 <syntax><IfModule [!]<var>module-file</var>|<var>module-identifier</var>> ...
1293 </IfModule></syntax>
1294 <contextlist><context>server config</context><context>virtual host</context>
1295 <context>directory</context><context>.htaccess</context>
1297 <override>All</override>
1298 <compatibility>Module identifiers are available in version 2.1 and
1299 later.</compatibility>
1302 <p>The <code><IfModule <var>test</var>>...</IfModule></code>
1303 section is used to mark directives that are conditional on the presence of
1304 a specific module. The directives within an <directive type="section"
1305 >IfModule</directive> section are only processed if the <var>test</var>
1306 is true. If <var>test</var> is false, everything between the start and
1307 end markers is ignored.</p>
1309 <p>The <var>test</var> in the <directive type="section"
1310 >IfModule</directive> section directive can be one of two forms:</p>
1313 <li><var>module</var></li>
1315 <li>!<var>module</var></li>
1318 <p>In the former case, the directives between the start and end
1319 markers are only processed if the module named <var>module</var>
1320 is included in Apache -- either compiled in or
1321 dynamically loaded using <directive module="mod_so"
1322 >LoadModule</directive>. The second format reverses the test,
1323 and only processes the directives if <var>module</var> is
1324 <strong>not</strong> included.</p>
1326 <p>The <var>module</var> argument can be either the module identifier or
1327 the file name of the module, at the time it was compiled. For example,
1328 <code>rewrite_module</code> is the identifier and
1329 <code>mod_rewrite.c</code> is the file name. If a module consists of
1330 several source files, use the name of the file containing the string
1331 <code>STANDARD20_MODULE_STUFF</code>.</p>
1333 <p><directive type="section">IfModule</directive> sections are
1334 nest-able, which can be used to implement simple multiple-module
1337 <note>This section should only be used if you need to have one
1338 configuration file that works whether or not a specific module
1339 is available. In normal operation, directives need not be
1340 placed in <directive type="section">IfModule</directive>
1343 </directivesynopsis>
1346 <name>Include</name>
1347 <description>Includes other configuration files from within
1348 the server configuration files</description>
1349 <syntax>Include <var>file-path</var>|<var>directory-path</var></syntax>
1350 <contextlist><context>server config</context><context>virtual host</context>
1351 <context>directory</context>
1353 <compatibility>Wildcard matching available in 2.0.41 and later</compatibility>
1356 <p>This directive allows inclusion of other configuration files
1357 from within the server configuration files.</p>
1359 <p>Shell-style (<code>fnmatch()</code>) wildcard characters can be used to
1360 include several files at once, in alphabetical order. In
1361 addition, if <directive>Include</directive> points to a directory,
1362 rather than a file, Apache will read all files in that directory
1363 and any subdirectory. But including entire directories is not
1364 recommended, because it is easy to accidentally leave temporary
1365 files in a directory that can cause <program>httpd</program> to
1368 <p>The file path specified may be an absolute path, or may be relative
1369 to the <directive module="core">ServerRoot</directive> directory.</p>
1374 Include /usr/local/apache2/conf/ssl.conf<br />
1375 Include /usr/local/apache2/conf/vhosts/*.conf
1378 <p>Or, providing paths relative to your <directive
1379 module="core">ServerRoot</directive> directory:</p>
1382 Include conf/ssl.conf<br />
1383 Include conf/vhosts/*.conf
1386 <p>Running <code>apachectl configtest</code> will give you a list
1387 of the files that are being processed during the configuration
1391 root@host# apachectl configtest<br />
1392 Processing config file: /usr/local/apache2/conf/ssl.conf<br />
1393 Processing config file: /usr/local/apache2/conf/vhosts/vhost1.conf<br />
1394 Processing config file: /usr/local/apache2/conf/vhosts/vhost2.conf<br />
1399 <seealso><program>apachectl</program></seealso>
1400 </directivesynopsis>
1403 <name>KeepAlive</name>
1404 <description>Enables HTTP persistent connections</description>
1405 <syntax>KeepAlive On|Off</syntax>
1406 <default>KeepAlive On</default>
1407 <contextlist><context>server config</context><context>virtual host</context>
1411 <p>The Keep-Alive extension to HTTP/1.0 and the persistent
1412 connection feature of HTTP/1.1 provide long-lived HTTP sessions
1413 which allow multiple requests to be sent over the same TCP
1414 connection. In some cases this has been shown to result in an
1415 almost 50% speedup in latency times for HTML documents with
1416 many images. To enable Keep-Alive connections, set
1417 <code>KeepAlive On</code>.</p>
1419 <p>For HTTP/1.0 clients, Keep-Alive connections will only be
1420 used if they are specifically requested by a client. In
1421 addition, a Keep-Alive connection with an HTTP/1.0 client can
1422 only be used when the length of the content is known in
1423 advance. This implies that dynamic content such as CGI output,
1424 SSI pages, and server-generated directory listings will
1425 generally not use Keep-Alive connections to HTTP/1.0 clients.
1426 For HTTP/1.1 clients, persistent connections are the default
1427 unless otherwise specified. If the client requests it, chunked
1428 encoding will be used in order to send content of unknown
1429 length over persistent connections.</p>
1432 <seealso><directive module="core">MaxKeepAliveRequests</directive></seealso>
1433 </directivesynopsis>
1436 <name>KeepAliveTimeout</name>
1437 <description>Amount of time the server will wait for subsequent
1438 requests on a persistent connection</description>
1439 <syntax>KeepAliveTimeout <var>seconds</var></syntax>
1440 <default>KeepAliveTimeout 15</default>
1441 <contextlist><context>server config</context><context>virtual host</context>
1445 <p>The number of seconds Apache will wait for a subsequent
1446 request before closing the connection. Once a request has been
1447 received, the timeout value specified by the
1448 <directive module="core">Timeout</directive> directive applies.</p>
1450 <p>Setting <directive>KeepAliveTimeout</directive> to a high value
1451 may cause performance problems in heavily loaded servers. The
1452 higher the timeout, the more server processes will be kept
1453 occupied waiting on connections with idle clients.</p>
1455 </directivesynopsis>
1457 <directivesynopsis type="section">
1459 <description>Restrict enclosed access controls to only certain HTTP
1460 methods</description>
1461 <syntax><Limit <var>method</var> [<var>method</var>] ... > ...
1462 </Limit></syntax>
1463 <contextlist><context>server config</context><context>virtual host</context>
1464 <context>directory</context><context>.htaccess</context>
1466 <override>All</override>
1469 <p>Access controls are normally effective for
1470 <strong>all</strong> access methods, and this is the usual
1471 desired behavior. <strong>In the general case, access control
1472 directives should not be placed within a
1473 <directive type="section">Limit</directive> section.</strong></p>
1475 <p>The purpose of the <directive type="section">Limit</directive>
1476 directive is to restrict the effect of the access controls to the
1477 nominated HTTP methods. For all other methods, the access
1478 restrictions that are enclosed in the <directive
1479 type="section">Limit</directive> bracket <strong>will have no
1480 effect</strong>. The following example applies the access control
1481 only to the methods <code>POST</code>, <code>PUT</code>, and
1482 <code>DELETE</code>, leaving all other methods unprotected:</p>
1485 <Limit POST PUT DELETE><br />
1487 Require valid-user<br />
1492 <p>The method names listed can be one or more of: <code>GET</code>,
1493 <code>POST</code>, <code>PUT</code>, <code>DELETE</code>,
1494 <code>CONNECT</code>, <code>OPTIONS</code>,
1495 <code>PATCH</code>, <code>PROPFIND</code>, <code>PROPPATCH</code>,
1496 <code>MKCOL</code>, <code>COPY</code>, <code>MOVE</code>,
1497 <code>LOCK</code>, and <code>UNLOCK</code>. <strong>The method name is
1498 case-sensitive.</strong> If <code>GET</code> is used it will also
1499 restrict <code>HEAD</code> requests. The <code>TRACE</code> method
1500 cannot be limited.</p>
1502 <note type="warning">A <directive type="section"
1503 module="core">LimitExcept</directive> section should always be
1504 used in preference to a <directive type="section"
1505 module="core">Limit</directive> section when restricting access,
1506 since a <directive type="section"
1507 module="core">LimitExcept</directive> section provides protection
1508 against arbitrary methods.</note>
1511 </directivesynopsis>
1513 <directivesynopsis type="section">
1514 <name>LimitExcept</name>
1515 <description>Restrict access controls to all HTTP methods
1516 except the named ones</description>
1517 <syntax><LimitExcept <var>method</var> [<var>method</var>] ... > ...
1518 </LimitExcept></syntax>
1519 <contextlist><context>server config</context><context>virtual host</context>
1520 <context>directory</context><context>.htaccess</context>
1522 <override>All</override>
1525 <p><directive type="section">LimitExcept</directive> and
1526 <code></LimitExcept></code> are used to enclose
1527 a group of access control directives which will then apply to any
1528 HTTP access method <strong>not</strong> listed in the arguments;
1529 i.e., it is the opposite of a <directive type="section"
1530 module="core">Limit</directive> section and can be used to control
1531 both standard and nonstandard/unrecognized methods. See the
1532 documentation for <directive module="core"
1533 type="section">Limit</directive> for more details.</p>
1538 <LimitExcept POST GET><br />
1540 Require valid-user<br />
1542 </LimitExcept>
1546 </directivesynopsis>
1549 <name>LimitInternalRecursion</name>
1550 <description>Determine maximum number of internal redirects and nested
1551 subrequests</description>
1552 <syntax>LimitInternalRecursion <var>number</var> [<var>number</var>]</syntax>
1553 <default>LimitInternalRecursion 10</default>
1554 <contextlist><context>server config</context><context>virtual host</context>
1556 <compatibility>Available in Apache 2.0.47 and later</compatibility>
1559 <p>An internal redirect happens, for example, when using the <directive
1560 module="mod_actions">Action</directive> directive, which internally
1561 redirects the original request to a CGI script. A subrequest is Apache's
1562 mechanism to find out what would happen for some URI if it were requested.
1563 For example, <module>mod_dir</module> uses subrequests to look for the
1564 files listed in the <directive module="mod_dir">DirectoryIndex</directive>
1567 <p><directive>LimitInternalRecursion</directive> prevents the server
1568 from crashing when entering an infinite loop of internal redirects or
1569 subrequests. Such loops are usually caused by misconfigurations.</p>
1571 <p>The directive stores two different limits, which are evaluated on
1572 per-request basis. The first <var>number</var> is the maximum number of
1573 internal redirects, that may follow each other. The second <var>number</var>
1574 determines, how deep subrequests may be nested. If you specify only one
1575 <var>number</var>, it will be assigned to both limits.</p>
1577 <example><title>Example</title>
1578 LimitInternalRecursion 5
1581 </directivesynopsis>
1584 <name>LimitRequestBody</name>
1585 <description>Restricts the total size of the HTTP request body sent
1586 from the client</description>
1587 <syntax>LimitRequestBody <var>bytes</var></syntax>
1588 <default>LimitRequestBody 0</default>
1589 <contextlist><context>server config</context><context>virtual host</context>
1590 <context>directory</context><context>.htaccess</context>
1592 <override>All</override>
1595 <p>This directive specifies the number of <var>bytes</var> from 0
1596 (meaning unlimited) to 2147483647 (2GB) that are allowed in a
1599 <p>The <directive>LimitRequestBody</directive> directive allows
1600 the user to set a limit on the allowed size of an HTTP request
1601 message body within the context in which the directive is given
1602 (server, per-directory, per-file or per-location). If the client
1603 request exceeds that limit, the server will return an error
1604 response instead of servicing the request. The size of a normal
1605 request message body will vary greatly depending on the nature of
1606 the resource and the methods allowed on that resource. CGI scripts
1607 typically use the message body for retrieving form information.
1608 Implementations of the <code>PUT</code> method will require
1609 a value at least as large as any representation that the server
1610 wishes to accept for that resource.</p>
1612 <p>This directive gives the server administrator greater
1613 control over abnormal client request behavior, which may be
1614 useful for avoiding some forms of denial-of-service
1617 <p>If, for example, you are permitting file upload to a particular
1618 location, and wish to limit the size of the uploaded file to 100K,
1619 you might use the following directive:</p>
1622 LimitRequestBody 102400
1626 </directivesynopsis>
1629 <name>LimitRequestFields</name>
1630 <description>Limits the number of HTTP request header fields that
1631 will be accepted from the client</description>
1632 <syntax>LimitRequestFields <var>number</var></syntax>
1633 <default>LimitRequestFields 100</default>
1634 <contextlist><context>server config</context></contextlist>
1637 <p><var>Number</var> is an integer from 0 (meaning unlimited) to
1638 32767. The default value is defined by the compile-time
1639 constant <code>DEFAULT_LIMIT_REQUEST_FIELDS</code> (100 as
1642 <p>The <directive>LimitRequestFields</directive> directive allows
1643 the server administrator to modify the limit on the number of
1644 request header fields allowed in an HTTP request. A server needs
1645 this value to be larger than the number of fields that a normal
1646 client request might include. The number of request header fields
1647 used by a client rarely exceeds 20, but this may vary among
1648 different client implementations, often depending upon the extent
1649 to which a user has configured their browser to support detailed
1650 content negotiation. Optional HTTP extensions are often expressed
1651 using request header fields.</p>
1653 <p>This directive gives the server administrator greater
1654 control over abnormal client request behavior, which may be
1655 useful for avoiding some forms of denial-of-service attacks.
1656 The value should be increased if normal clients see an error
1657 response from the server that indicates too many fields were
1658 sent in the request.</p>
1663 LimitRequestFields 50
1667 </directivesynopsis>
1670 <name>LimitRequestFieldSize</name>
1671 <description>Limits the size of the HTTP request header allowed from the
1672 client</description>
1673 <syntax>LimitRequestFieldsize <var>bytes</var></syntax>
1674 <default>LimitRequestFieldsize 8190</default>
1675 <contextlist><context>server config</context></contextlist>
1678 <p>This directive specifies the number of <var>bytes</var> from 0
1679 to the value of the compile-time constant
1680 <code>DEFAULT_LIMIT_REQUEST_FIELDSIZE</code> (8190 as
1681 distributed) that will be allowed in an HTTP request
1684 <p>The <directive>LimitRequestFieldSize</directive> directive
1685 allows the server administrator to reduce the limit on the allowed
1686 size of an HTTP request header field below the normal input buffer
1687 size compiled with the server. A server needs this value to be
1688 large enough to hold any one header field from a normal client
1689 request. The size of a normal request header field will vary
1690 greatly among different client implementations, often depending
1691 upon the extent to which a user has configured their browser to
1692 support detailed content negotiation.</p>
1694 <p>This directive gives the server administrator greater
1695 control over abnormal client request behavior, which may be
1696 useful for avoiding some forms of denial-of-service attacks.</p>
1701 LimitRequestFieldSize 4094
1704 <note>Under normal conditions, the value should not be changed from
1708 </directivesynopsis>
1711 <name>LimitRequestLine</name>
1712 <description>Limit the size of the HTTP request line that will be accepted
1713 from the client</description>
1714 <syntax>LimitRequestLine <var>bytes</var></syntax>
1715 <default>LimitRequestLine 8190</default>
1716 <contextlist><context>server config</context></contextlist>
1719 <p>This directive sets the number of <var>bytes</var> from 0 to
1720 the value of the compile-time constant
1721 <code>DEFAULT_LIMIT_REQUEST_LINE</code> (8190 as distributed)
1722 that will be allowed on the HTTP request-line.</p>
1724 <p>The <directive>LimitRequestLine</directive> directive allows
1725 the server administrator to reduce the limit on the allowed size
1726 of a client's HTTP request-line below the normal input buffer size
1727 compiled with the server. Since the request-line consists of the
1728 HTTP method, URI, and protocol version, the
1729 <directive>LimitRequestLine</directive> directive places a
1730 restriction on the length of a request-URI allowed for a request
1731 on the server. A server needs this value to be large enough to
1732 hold any of its resource names, including any information that
1733 might be passed in the query part of a <code>GET</code> request.</p>
1735 <p>This directive gives the server administrator greater
1736 control over abnormal client request behavior, which may be
1737 useful for avoiding some forms of denial-of-service attacks.</p>
1742 LimitRequestLine 4094
1745 <note>Under normal conditions, the value should not be changed from
1748 </directivesynopsis>
1751 <name>LimitXMLRequestBody</name>
1752 <description>Limits the size of an XML-based request body</description>
1753 <syntax>LimitXMLRequestBody <var>bytes</var></syntax>
1754 <default>LimitXMLRequestBody 1000000</default>
1755 <contextlist><context>server config</context><context>virtual host</context>
1756 <context>directory</context><context>.htaccess</context></contextlist>
1757 <override>All</override>
1760 <p>Limit (in bytes) on maximum size of an XML-based request
1761 body. A value of <code>0</code> will disable any checking.</p>
1766 LimitXMLRequestBody 0
1770 </directivesynopsis>
1772 <directivesynopsis type="section">
1773 <name>Location</name>
1774 <description>Applies the enclosed directives only to matching
1776 <syntax><Location
1777 <var>URL-path</var>|<var>URL</var>> ... </Location></syntax>
1778 <contextlist><context>server config</context><context>virtual host</context>
1782 <p>The <directive type="section">Location</directive> directive
1783 limits the scope of the enclosed directives by URL. It is similar to the
1784 <directive type="section" module="core">Directory</directive>
1785 directive, and starts a subsection which is terminated with a
1786 <code></Location></code> directive. <directive
1787 type="section">Location</directive> sections are processed in the
1788 order they appear in the configuration file, after the <directive
1789 type="section" module="core">Directory</directive> sections and
1790 <code>.htaccess</code> files are read, and after the <directive
1791 type="section" module="core">Files</directive> sections.</p>
1793 <p><directive type="section">Location</directive> sections operate
1794 completely outside the filesystem. This has several consequences.
1795 Most importantly, <directive type="section">Location</directive>
1796 directives should not be used to control access to filesystem
1797 locations. Since several different URLs may map to the same
1798 filesystem location, such access controls may by circumvented.</p>
1800 <note><title>When to use <directive
1801 type="section">Location</directive></title>
1803 <p>Use <directive type="section">Location</directive> to apply
1804 directives to content that lives outside the filesystem. For
1805 content that lives in the filesystem, use <directive
1806 type="section" module="core">Directory</directive> and <directive
1807 type="section" module="core">Files</directive>. An exception is
1808 <code><Location /></code>, which is an easy way to
1809 apply a configuration to the entire server.</p>
1812 <p>For all origin (non-proxy) requests, the URL to be matched is a
1813 URL-path of the form <code>/path/</code>. No scheme, hostname,
1814 port, or query string may be included. For proxy requests, the
1815 URL to be matched is of the form
1816 <code>scheme://servername/path</code>, and you must include the
1819 <p>The URL may use wildcards. In a wild-card string, <code>?</code> matches
1820 any single character, and <code>*</code> matches any sequences of
1824 expressions can also be used, with the addition of the
1825 <code>~</code> character. For example:</p>
1828 <Location ~ "/(extra|special)/data">
1831 <p>would match URLs that contained the substring <code>/extra/data</code>
1832 or <code>/special/data</code>. The directive <directive
1833 type="section" module="core">LocationMatch</directive> behaves
1834 identical to the regex version of <directive
1835 type="section">Location</directive>.</p>
1837 <p>The <directive type="section">Location</directive>
1838 functionality is especially useful when combined with the
1839 <directive module="core">SetHandler</directive>
1840 directive. For example, to enable status requests, but allow them
1841 only from browsers at <code>foo.com</code>, you might use:</p>
1844 <Location /status><br />
1846 SetHandler server-status<br />
1847 Order Deny,Allow<br />
1849 Allow from .foo.com<br />
1854 <note><title>Note about / (slash)</title>
1855 <p>The slash character has special meaning depending on where in a
1856 URL it appears. People may be used to its behavior in the filesystem
1857 where multiple adjacent slashes are frequently collapsed to a single
1858 slash (<em>i.e.</em>, <code>/home///foo</code> is the same as
1859 <code>/home/foo</code>). In URL-space this is not necessarily true.
1860 The <directive type="section" module="core">LocationMatch</directive>
1861 directive and the regex version of <directive type="section"
1862 >Location</directive> require you to explicitly specify multiple
1863 slashes if that is your intention.</p>
1865 <p>For example, <code><LocationMatch ^/abc></code> would match
1866 the request URL <code>/abc</code> but not the request URL <code>
1867 //abc</code>. The (non-regex) <directive type="section"
1868 >Location</directive> directive behaves similarly when used for
1869 proxy requests. But when (non-regex) <directive type="section"
1870 >Location</directive> is used for non-proxy requests it will
1871 implicitly match multiple slashes with a single slash. For example,
1872 if you specify <code><Location /abc/def></code> and the
1873 request is to <code>/abc//def</code> then it will match.</p>
1876 <seealso><a href="../sections.html">How <Directory>, <Location>
1877 and <Files> sections work</a> for an explanation of how these
1878 different sections are combined when a request is received</seealso>
1879 </directivesynopsis>
1881 <directivesynopsis type="section">
1882 <name>LocationMatch</name>
1883 <description>Applies the enclosed directives only to regular-expression
1884 matching URLs</description>
1885 <syntax><LocationMatch
1886 <var>regex</var>> ... </LocationMatch></syntax>
1887 <contextlist><context>server config</context><context>virtual host</context>
1891 <p>The <directive type="section">LocationMatch</directive> directive
1892 limits the scope of the enclosed directives by URL, in an identical manner
1893 to <directive module="core" type="section">Location</directive>. However,
1894 it takes a regular expression as an argument instead of a simple
1895 string. For example:</p>
1898 <LocationMatch "/(extra|special)/data">
1901 <p>would match URLs that contained the substring <code>/extra/data</code>
1902 or <code>/special/data</code>.</p>
1905 <seealso><a href="../sections.html">How <Directory>, <Location>
1906 and <Files> sections work</a> for an explanation of how these
1907 different sections are combined when a request is received</seealso>
1908 </directivesynopsis>
1911 <name>LogLevel</name>
1912 <description>Controls the verbosity of the ErrorLog</description>
1913 <syntax>LogLevel <var>level</var></syntax>
1914 <default>LogLevel warn</default>
1915 <contextlist><context>server config</context><context>virtual host</context>
1919 <p><directive>LogLevel</directive> adjusts the verbosity of the
1920 messages recorded in the error logs (see <directive
1921 module="core">ErrorLog</directive> directive). The following
1922 <var>level</var>s are available, in order of decreasing
1926 <columnspec><column width=".2"/><column width=".3"/><column width=".5"/>
1929 <th><strong>Level</strong> </th>
1931 <th><strong>Description</strong> </th>
1933 <th><strong>Example</strong> </th>
1937 <td><code>emerg</code> </td>
1939 <td>Emergencies - system is unusable.</td>
1941 <td>"Child cannot open lock file. Exiting"</td>
1945 <td><code>alert</code> </td>
1947 <td>Action must be taken immediately.</td>
1949 <td>"getpwuid: couldn't determine user name from uid"</td>
1953 <td><code>crit</code> </td>
1955 <td>Critical Conditions.</td>
1957 <td>"socket: Failed to get a socket, exiting child"</td>
1961 <td><code>error</code> </td>
1963 <td>Error conditions.</td>
1965 <td>"Premature end of script headers"</td>
1969 <td><code>warn</code> </td>
1971 <td>Warning conditions.</td>
1973 <td>"child process 1234 did not exit, sending another
1978 <td><code>notice</code> </td>
1980 <td>Normal but significant condition.</td>
1982 <td>"httpd: caught SIGBUS, attempting to dump core in
1987 <td><code>info</code> </td>
1989 <td>Informational.</td>
1991 <td>"Server seems busy, (you may need to increase
1992 StartServers, or Min/MaxSpareServers)..."</td>
1996 <td><code>debug</code> </td>
1998 <td>Debug-level messages</td>
2000 <td>"Opening config file ..."</td>
2004 <p>When a particular level is specified, messages from all
2005 other levels of higher significance will be reported as well.
2006 <em>E.g.</em>, when <code>LogLevel info</code> is specified,
2007 then messages with log levels of <code>notice</code> and
2008 <code>warn</code> will also be posted.</p>
2010 <p>Using a level of at least <code>crit</code> is
2019 <note><title>Note</title>
2020 <p>When logging to a regular file messages of the level
2021 <code>notice</code> cannot be suppressed and thus are always
2022 logged. However, this doesn't apply when logging is done
2023 using <code>syslog</code>.</p>
2026 </directivesynopsis>
2029 <name>MaxKeepAliveRequests</name>
2030 <description>Number of requests allowed on a persistent
2031 connection</description>
2032 <syntax>MaxKeepAliveRequests <var>number</var></syntax>
2033 <default>MaxKeepAliveRequests 100</default>
2034 <contextlist><context>server config</context><context>virtual host</context>
2038 <p>The <directive>MaxKeepAliveRequests</directive> directive
2039 limits the number of requests allowed per connection when
2040 <directive module="core" >KeepAlive</directive> is on. If it is
2041 set to <code>0</code>, unlimited requests will be allowed. We
2042 recommend that this setting be kept to a high value for maximum
2043 server performance.</p>
2048 MaxKeepAliveRequests 500
2051 </directivesynopsis>
2054 <name>NameVirtualHost</name>
2055 <description>Designates an IP address for name-virtual
2056 hosting</description>
2057 <syntax>NameVirtualHost <var>addr</var>[:<var>port</var>]</syntax>
2058 <contextlist><context>server config</context></contextlist>
2061 <p>The <directive>NameVirtualHost</directive> directive is a
2062 required directive if you want to configure <a
2063 href="../vhosts/">name-based virtual hosts</a>.</p>
2065 <p>Although <var>addr</var> can be hostname it is recommended
2066 that you always use an IP address, e.g.</p>
2069 NameVirtualHost 111.22.33.44
2072 <p>With the <directive>NameVirtualHost</directive> directive you
2073 specify the IP address on which the server will receive requests
2074 for the name-based virtual hosts. This will usually be the address
2075 to which your name-based virtual host names resolve. In cases
2076 where a firewall or other proxy receives the requests and forwards
2077 them on a different IP address to the server, you must specify the
2078 IP address of the physical interface on the machine which will be
2079 servicing the requests. If you have multiple name-based hosts on
2080 multiple addresses, repeat the directive for each address.</p>
2082 <note><title>Note</title>
2083 <p>Note, that the "main server" and any <code>_default_</code> servers
2084 will <strong>never</strong> be served for a request to a
2085 <directive>NameVirtualHost</directive> IP address (unless for some
2086 reason you specify <directive>NameVirtualHost</directive> but then
2087 don't define any <directive>VirtualHost</directive>s for that
2091 <p>Optionally you can specify a port number on which the
2092 name-based virtual hosts should be used, e.g.</p>
2095 NameVirtualHost 111.22.33.44:8080
2098 <p>IPv6 addresses must be enclosed in square brackets, as shown
2099 in the following example:</p>
2102 NameVirtualHost [fe80::a00:20ff:fea7:ccea]:8080
2105 <p>To receive requests on all interfaces, you can use an argument of
2112 <note><title>Argument to <directive type="section">VirtualHost</directive>
2114 <p>Note that the argument to the <directive
2115 type="section">VirtualHost</directive> directive must
2116 exactly match the argument to the <directive
2117 >NameVirtualHost</directive> directive.</p>
2120 NameVirtualHost 1.2.3.4<br />
2121 <VirtualHost 1.2.3.4><br />
2123 </VirtualHost><br />
2128 <seealso><a href="../vhosts/">Virtual Hosts
2129 documentation</a></seealso>
2131 </directivesynopsis>
2134 <name>Options</name>
2135 <description>Configures what features are available in a particular
2136 directory</description>
2138 [+|-]<var>option</var> [[+|-]<var>option</var>] ...</syntax>
2139 <default>Options All</default>
2140 <contextlist><context>server config</context><context>virtual host</context>
2141 <context>directory</context><context>.htaccess</context>
2143 <override>Options</override>
2146 <p>The <directive>Options</directive> directive controls which
2147 server features are available in a particular directory.</p>
2149 <p><var>option</var> can be set to <code>None</code>, in which
2150 case none of the extra features are enabled, or one or more of
2154 <dt><code>All</code></dt>
2156 <dd>All options except for <code>MultiViews</code>. This is the default
2159 <dt><code>ExecCGI</code></dt>
2162 Execution of CGI scripts using <module>mod_cgi</module>
2165 <dt><code>FollowSymLinks</code></dt>
2169 The server will follow symbolic links in this directory.
2171 <p>Even though the server follows the symlink it does <em>not</em>
2172 change the pathname used to match against <directive type="section"
2173 module="core">Directory</directive> sections.</p>
2174 <p>Note also, that this option <strong>gets ignored</strong> if set
2175 inside a <directive type="section" module="core">Location</directive>
2179 <dt><code>Includes</code></dt>
2182 Server-side includes provided by <module>mod_include</module>
2185 <dt><code>IncludesNOEXEC</code></dt>
2189 Server-side includes are permitted, but the <code>#exec
2190 cmd</code> and <code>#exec cgi</code> are disabled. It is still
2191 possible to <code>#include virtual</code> CGI scripts from
2192 <directive module="mod_alias">ScriptAlias</directive>ed
2195 <dt><code>Indexes</code></dt>
2198 If a URL which maps to a directory is requested, and there
2199 is no <directive module="mod_dir">DirectoryIndex</directive>
2200 (<em>e.g.</em>, <code>index.html</code>) in that directory, then
2201 <module>mod_autoindex</module> will return a formatted listing
2202 of the directory.</dd>
2204 <dt><code>MultiViews</code></dt>
2207 <a href="../content-negotiation.html">Content negotiated</a>
2208 "MultiViews" are allowed using
2209 <module>mod_negotiation</module>.</dd>
2211 <dt><code>SymLinksIfOwnerMatch</code></dt>
2213 <dd>The server will only follow symbolic links for which the
2214 target file or directory is owned by the same user id as the
2217 <note><title>Note</title> This option gets ignored if
2218 set inside a <directive module="core"
2219 type="section">Location</directive> section.</note>
2223 <p>Normally, if multiple <directive>Options</directive> could
2224 apply to a directory, then the most specific one is used and
2225 others are ignored; the options are not merged. (See <a
2226 href="../sections.html#mergin">how sections are merged</a>.)
2227 However if <em>all</em> the options on the
2228 <directive>Options</directive> directive are preceded by a
2229 <code>+</code> or <code>-</code> symbol, the options are
2230 merged. Any options preceded by a <code>+</code> are added to the
2231 options currently in force, and any options preceded by a
2232 <code>-</code> are removed from the options currently in
2235 <p>For example, without any <code>+</code> and <code>-</code> symbols:</p>
2238 <Directory /web/docs><br />
2240 Options Indexes FollowSymLinks<br />
2242 </Directory><br />
2244 <Directory /web/docs/spec><br />
2246 Options Includes<br />
2251 <p>then only <code>Includes</code> will be set for the
2252 <code>/web/docs/spec</code> directory. However if the second
2253 <directive>Options</directive> directive uses the <code>+</code> and
2254 <code>-</code> symbols:</p>
2257 <Directory /web/docs><br />
2259 Options Indexes FollowSymLinks<br />
2261 </Directory><br />
2263 <Directory /web/docs/spec><br />
2265 Options +Includes -Indexes<br />
2270 <p>then the options <code>FollowSymLinks</code> and
2271 <code>Includes</code> are set for the <code>/web/docs/spec</code>
2274 <note><title>Note</title>
2275 <p>Using <code>-IncludesNOEXEC</code> or
2276 <code>-Includes</code> disables server-side includes completely
2277 regardless of the previous setting.</p>
2280 <p>The default in the absence of any other settings is
2281 <code>All</code>.</p>
2283 </directivesynopsis>
2286 <name>Require</name>
2287 <description>Selects which authenticated users can access
2288 a resource</description>
2289 <syntax>Require <var>entity-name</var> [<var>entity-name</var>] ...</syntax>
2290 <contextlist><context>directory</context><context>.htaccess</context>
2292 <override>AuthConfig</override>
2295 <p>This directive selects which authenticated users can access
2296 a directory. The allowed syntaxes are:</p>
2299 <dt><code>Require user <var>userid</var> [<var>userid</var>]
2301 <dd>Only the named users can access the resource.</dd>
2303 <dt><code>Require group <var>group-name</var> [<var>group-name</var>]
2305 <dd>Only users in the named groups can access the resource.</dd>
2307 <dt><code>Require valid-user</code></dt>
2308 <dd>All valid users can access the resource.</dd>
2311 <p><directive>Require</directive> must be accompanied by
2312 <directive module="core">AuthName</directive> and <directive
2313 module="core">AuthType</directive> directives, and directives such
2314 as <directive module="mod_authn_file">AuthUserFile</directive>
2315 and <directive module="mod_authz_groupfile">AuthGroupFile</directive> (to
2316 define users and groups) in order to work correctly. Example:</p>
2319 AuthType Basic<br />
2320 AuthName "Restricted Directory"<br />
2321 AuthUserFile /web/users<br />
2322 AuthGroupFile /web/groups<br />
2326 <p>Access controls which are applied in this way are effective for
2327 <strong>all</strong> methods. <strong>This is what is normally
2328 desired.</strong> If you wish to apply access controls only to
2329 specific methods, while leaving other methods unprotected, then
2330 place the <directive>Require</directive> statement into a
2331 <directive module="core" type="section">Limit</directive>
2334 <seealso><directive module="core">Satisfy</directive></seealso>
2335 <seealso><module>mod_authz_host</module></seealso>
2336 </directivesynopsis>
2339 <name>RLimitCPU</name>
2340 <description>Limits the CPU consumption of processes launched
2341 by Apache children</description>
2342 <syntax>RLimitCPU <var>seconds</var>|max [<var>seconds</var>|max]</syntax>
2343 <default>Unset; uses operating system defaults</default>
2344 <contextlist><context>server config</context><context>virtual host</context>
2345 <context>directory</context><context>.htaccess</context></contextlist>
2346 <override>All</override>
2349 <p>Takes 1 or 2 parameters. The first parameter sets the soft
2350 resource limit for all processes and the second parameter sets
2351 the maximum resource limit. Either parameter can be a number,
2352 or <code>max</code> to indicate to the server that the limit should
2353 be set to the maximum allowed by the operating system
2354 configuration. Raising the maximum resource limit requires that
2355 the server is running as <code>root</code>, or in the initial startup
2358 <p>This applies to processes forked off from Apache children
2359 servicing requests, not the Apache children themselves. This
2360 includes CGI scripts and SSI exec commands, but not any
2361 processes forked off from the Apache parent such as piped
2364 <p>CPU resource limits are expressed in seconds per
2367 <seealso><directive module="core">RLimitMEM</directive></seealso>
2368 <seealso><directive module="core">RLimitNPROC</directive></seealso>
2369 </directivesynopsis>
2372 <name>RLimitMEM</name>
2373 <description>Limits the memory consumption of processes launched
2374 by Apache children</description>
2375 <syntax>RLimitMEM <var>bytes</var>|max [<var>bytes</var>|max]</syntax>
2376 <default>Unset; uses operating system defaults</default>
2377 <contextlist><context>server config</context><context>virtual host</context>
2378 <context>directory</context><context>.htaccess</context></contextlist>
2379 <override>All</override>
2382 <p>Takes 1 or 2 parameters. The first parameter sets the soft
2383 resource limit for all processes and the second parameter sets
2384 the maximum resource limit. Either parameter can be a number,
2385 or <code>max</code> to indicate to the server that the limit should
2386 be set to the maximum allowed by the operating system
2387 configuration. Raising the maximum resource limit requires that
2388 the server is running as <code>root</code>, or in the initial startup
2391 <p>This applies to processes forked off from Apache children
2392 servicing requests, not the Apache children themselves. This
2393 includes CGI scripts and SSI exec commands, but not any
2394 processes forked off from the Apache parent such as piped
2397 <p>Memory resource limits are expressed in bytes per
2400 <seealso><directive module="core">RLimitCPU</directive></seealso>
2401 <seealso><directive module="core">RLimitNPROC</directive></seealso>
2402 </directivesynopsis>
2405 <name>RLimitNPROC</name>
2406 <description>Limits the number of processes that can be launched by
2407 processes launched by Apache children</description>
2408 <syntax>RLimitNPROC <var>number</var>|max [<var>number</var>|max]</syntax>
2409 <default>Unset; uses operating system defaults</default>
2410 <contextlist><context>server config</context><context>virtual host</context>
2411 <context>directory</context><context>.htaccess</context></contextlist>
2412 <override>All</override>
2415 <p>Takes 1 or 2 parameters. The first parameter sets the soft
2416 resource limit for all processes and the second parameter sets
2417 the maximum resource limit. Either parameter can be a number,
2418 or <code>max</code> to indicate to the server that the limit
2419 should be set to the maximum allowed by the operating system
2420 configuration. Raising the maximum resource limit requires that
2421 the server is running as <code>root</code>, or in the initial startup
2424 <p>This applies to processes forked off from Apache children
2425 servicing requests, not the Apache children themselves. This
2426 includes CGI scripts and SSI exec commands, but not any
2427 processes forked off from the Apache parent such as piped
2430 <p>Process limits control the number of processes per user.</p>
2432 <note><title>Note</title>
2433 <p>If CGI processes are <strong>not</strong> running
2434 under user ids other than the web server user id, this directive
2435 will limit the number of processes that the server itself can
2436 create. Evidence of this situation will be indicated by
2437 <strong><code>cannot fork</code></strong> messages in the
2438 <code>error_log</code>.</p>
2441 <seealso><directive module="core">RLimitMEM</directive></seealso>
2442 <seealso><directive module="core">RLimitCPU</directive></seealso>
2443 </directivesynopsis>
2446 <name>Satisfy</name>
2447 <description>Interaction between host-level access control and
2448 user authentication</description>
2449 <syntax>Satisfy Any|All</syntax>
2450 <default>Satisfy All</default>
2451 <contextlist><context>directory</context><context>.htaccess</context>
2453 <override>AuthConfig</override>
2454 <compatibility>Influenced by <directive module="core" type="section"
2455 >Limit</directive> and <directive module="core"
2456 type="section">LimitExcept</directive> in version 2.0.51 and
2457 later</compatibility>
2460 <p>Access policy if both <directive
2461 module="mod_authz_host">Allow</directive> and <directive
2462 module="core">Require</directive> used. The parameter can be
2463 either <code>All</code> or <code>Any</code>. This directive is only
2464 useful if access to a particular area is being restricted by both
2465 username/password <em>and</em> client host address. In this case
2466 the default behavior (<code>All</code>) is to require that the client
2467 passes the address access restriction <em>and</em> enters a valid
2468 username and password. With the <code>Any</code> option the client will be
2469 granted access if they either pass the host restriction or enter a
2470 valid username and password. This can be used to password restrict
2471 an area, but to let clients from particular addresses in without
2472 prompting for a password.</p>
2474 <p>For example, if you wanted to let people on your network have
2475 unrestricted access to a portion of your website, but require that
2476 people outside of your network provide a password, you could use a
2477 configuration similar to the following:</p>
2480 Require valid-user<br />
2481 Allow from 192.168.1<br />
2485 <p>Since version 2.0.51 <directive>Satisfy</directive> directives can
2486 be restricted to particular methods by <directive module="core"
2487 type="section">Limit</directive> and <directive module="core" type="section"
2488 >LimitExcept</directive> sections.</p>
2490 <seealso><directive module="mod_authz_host">Allow</directive></seealso>
2491 <seealso><directive module="core">Require</directive></seealso>
2492 </directivesynopsis>
2495 <name>ScriptInterpreterSource</name>
2496 <description>Technique for locating the interpreter for CGI
2497 scripts</description>
2498 <syntax>ScriptInterpreterSource Registry|Registry-Strict|Script</syntax>
2499 <default>ScriptInterpreterSource Script</default>
2500 <contextlist><context>server config</context><context>virtual host</context>
2501 <context>directory</context><context>.htaccess</context></contextlist>
2502 <override>FileInfo</override>
2503 <compatibility>Win32 only;
2504 option <code>Registry-Strict</code> is available in Apache 2.0 and
2505 later</compatibility>
2508 <p>This directive is used to control how Apache finds the
2509 interpreter used to run CGI scripts. The default setting is
2510 <code>Script</code>. This causes Apache to use the interpreter pointed to
2511 by the shebang line (first line, starting with <code>#!</code>) in the
2512 script. On Win32 systems this line usually looks like:</p>
2515 #!C:/Perl/bin/perl.exe
2518 <p>or, if <code>perl</code> is in the <code>PATH</code>, simply:</p>
2524 <p>Setting <code>ScriptInterpreterSource Registry</code> will
2525 cause the Windows Registry tree <code>HKEY_CLASSES_ROOT</code> to be
2526 searched using the script file extension (e.g., <code>.pl</code>) as a
2527 search key. The command defined by the registry subkey
2528 <code>Shell\ExecCGI\Command</code> or, if it does not exist, by the subkey
2529 <code>Shell\Open\Command</code> is used to open the script file. If the
2530 registry keys cannot be found, Apache falls back to the behavior of the
2531 <code>Script</code> option.</p>
2533 <note type="warning"><title>Security</title>
2534 <p>Be careful when using <code>ScriptInterpreterSource
2535 Registry</code> with <directive
2536 module="mod_alias">ScriptAlias</directive>'ed directories, because
2537 Apache will try to execute <strong>every</strong> file within this
2538 directory. The <code>Registry</code> setting may cause undesired
2539 program calls on files which are typically not executed. For
2540 example, the default open command on <code>.htm</code> files on
2541 most Windows systems will execute Microsoft Internet Explorer, so
2542 any HTTP request for an <code>.htm</code> file existing within the
2543 script directory would start the browser in the background on the
2544 server. This is a good way to crash your system within a minute or
2548 <p>The option <code>Registry-Strict</code> which is new in Apache
2549 2.0 does the same thing as <code>Registry</code> but uses only the
2550 subkey <code>Shell\ExecCGI\Command</code>. The
2551 <code>ExecCGI</code> key is not a common one. It must be
2552 configured manually in the windows registry and hence prevents
2553 accidental program calls on your system.</p>
2555 </directivesynopsis>
2558 <name>ServerAdmin</name>
2559 <description>Email address that the server includes in error
2560 messages sent to the client</description>
2561 <syntax>ServerAdmin <var>email-address</var>|<var>URL</var></syntax>
2562 <contextlist><context>server config</context><context>virtual host</context>
2566 <p>The <directive>ServerAdmin</directive> sets the contact address
2567 that the server includes in any error messages it returns to the
2568 client. If the <code>httpd</code> doesn't recognize the supplied argument
2570 assumes, that it's an <var>email-address</var> and prepends it with
2571 <code>mailto:</code> in hyperlink targets. However, it's recommended to
2572 actually use an email address, since there are a lot of CGI scripts that
2573 make that assumption. If you want to use an URL, it should point to another
2574 server under your control. Otherwise users may not be able to contact you in
2577 <p>It may be worth setting up a dedicated address for this, e.g.</p>
2580 ServerAdmin www-admin@foo.example.com
2582 <p>as users do not always mention that they are talking about the
2585 </directivesynopsis>
2588 <name>ServerAlias</name>
2589 <description>Alternate names for a host used when matching requests
2590 to name-virtual hosts</description>
2591 <syntax>ServerAlias <var>hostname</var> [<var>hostname</var>] ...</syntax>
2592 <contextlist><context>virtual host</context></contextlist>
2595 <p>The <directive>ServerAlias</directive> directive sets the
2596 alternate names for a host, for use with <a
2597 href="../vhosts/name-based.html">name-based virtual hosts</a>.</p>
2600 <VirtualHost *><br />
2601 ServerName server.domain.com<br />
2602 ServerAlias server server2.domain.com server2<br />
2604 </VirtualHost>
2607 <seealso><a href="../vhosts/">Apache Virtual Host documentation</a></seealso>
2608 </directivesynopsis>
2611 <name>ServerName</name>
2612 <description>Hostname and port that the server uses to identify
2613 itself</description>
2614 <syntax>ServerName <var>fully-qualified-domain-name</var>[:<var>port</var>]</syntax>
2615 <contextlist><context>server config</context><context>virtual host</context>
2617 <compatibility>In version 2.0, this
2618 directive supersedes the functionality of the <directive>Port</directive>
2619 directive from version 1.3.</compatibility>
2622 <p>The <directive>ServerName</directive> directive sets the hostname and
2623 port that the server uses to identify itself. This is used when
2624 creating redirection URLs. For example, if the name of the
2625 machine hosting the web server is <code>simple.example.com</code>,
2626 but the machine also has the DNS alias <code>www.example.com</code>
2627 and you wish the web server to be so identified, the following
2628 directive should be used:</p>
2631 ServerName www.example.com:80
2634 <p>If no <directive>ServerName</directive> is specified, then the
2635 server attempts to deduce the hostname by performing a reverse
2636 lookup on the IP address. If no port is specified in the
2637 <directive>ServerName</directive>, then the server will use the port
2639 request. For optimal reliability and predictability, you should
2640 specify an explicit hostname and port using the
2641 <directive>ServerName</directive> directive.</p>
2643 <p>If you are using <a
2644 href="../vhosts/name-based.html">name-based virtual hosts</a>,
2645 the <directive>ServerName</directive> inside a
2646 <directive type="section" module="core">VirtualHost</directive>
2647 section specifies what hostname must appear in the request's
2648 <code>Host:</code> header to match this virtual host.</p>
2650 <p>See the description of the
2651 <directive module="core">UseCanonicalName</directive> directive for
2652 settings which determine whether self-referential URL's (e.g., by the
2653 <module>mod_dir</module> module) will refer to the
2654 specified port, or to the port number given in the client's request.
2658 <seealso><a href="../dns-caveats.html">Issues Regarding DNS and
2659 Apache</a></seealso>
2660 <seealso><a href="../vhosts/">Apache virtual host
2661 documentation</a></seealso>
2662 <seealso><directive module="core">UseCanonicalName</directive></seealso>
2663 <seealso><directive module="core">NameVirtualHost</directive></seealso>
2664 <seealso><directive module="core">ServerAlias</directive></seealso>
2665 </directivesynopsis>
2668 <name>ServerPath</name>
2669 <description>Legacy URL pathname for a name-based virtual host that
2670 is accessed by an incompatible browser</description>
2671 <syntax>ServerPath <var>URL-path</var></syntax>
2672 <contextlist><context>virtual host</context></contextlist>
2675 <p>The <directive>ServerPath</directive> directive sets the legacy
2676 URL pathname for a host, for use with <a
2677 href="../vhosts/">name-based virtual hosts</a>.</p>
2679 <seealso><a href="../vhosts/">Apache Virtual Host documentation</a></seealso>
2680 </directivesynopsis>
2683 <name>ServerRoot</name>
2684 <description>Base directory for the server installation</description>
2685 <syntax>ServerRoot <var>directory-path</var></syntax>
2686 <default>ServerRoot /usr/local/apache</default>
2687 <contextlist><context>server config</context></contextlist>
2690 <p>The <directive>ServerRoot</directive> directive sets the
2691 directory in which the server lives. Typically it will contain the
2692 subdirectories <code>conf/</code> and <code>logs/</code>. Relative
2693 paths in other configuration directives (such as <directive
2694 module="core">Include</directive> or <directive
2695 module="mod_so">LoadModule</directive>, for example) are taken as
2696 relative to this directory.</p>
2698 <example><title>Example</title>
2699 ServerRoot /home/httpd
2703 <seealso><a href="../invoking.html">the <code>-d</code>
2704 option to <code>httpd</code></a></seealso>
2705 <seealso><a href="../misc/security_tips.html#serverroot">the
2706 security tips</a> for information on how to properly set
2707 permissions on the <directive>ServerRoot</directive></seealso>
2708 </directivesynopsis>
2711 <name>ServerSignature</name>
2712 <description>Configures the footer on server-generated documents</description>
2713 <syntax>ServerSignature On|Off|EMail</syntax>
2714 <default>ServerSignature Off</default>
2715 <contextlist><context>server config</context><context>virtual host</context>
2716 <context>directory</context><context>.htaccess</context>
2718 <override>All</override>
2721 <p>The <directive>ServerSignature</directive> directive allows the
2722 configuration of a trailing footer line under server-generated
2723 documents (error messages, <module>mod_proxy</module> ftp directory
2724 listings, <module>mod_info</module> output, ...). The reason why you
2725 would want to enable such a footer line is that in a chain of proxies,
2726 the user often has no possibility to tell which of the chained servers
2727 actually produced a returned error message.</p>
2729 <p>The <code>Off</code>
2730 setting, which is the default, suppresses the footer line (and is
2731 therefore compatible with the behavior of Apache-1.2 and
2732 below). The <code>On</code> setting simply adds a line with the
2733 server version number and <directive
2734 module="core">ServerName</directive> of the serving virtual host,
2735 and the <code>EMail</code> setting additionally creates a
2736 "mailto:" reference to the <directive
2737 module="core">ServerAdmin</directive> of the referenced
2740 <p>After version 2.0.44, the details of the server version number
2741 presented are controlled by the <directive
2742 module="core">ServerTokens</directive> directive.</p>
2744 <seealso><directive module="core">ServerTokens</directive></seealso>
2745 </directivesynopsis>
2748 <name>ServerTokens</name>
2749 <description>Configures the <code>Server</code> HTTP response
2750 header</description>
2751 <syntax>ServerTokens Major|Minor|Min[imal]|Prod[uctOnly]|OS|Full</syntax>
2752 <default>ServerTokens Full</default>
2753 <contextlist><context>server config</context></contextlist>
2756 <p>This directive controls whether <code>Server</code> response
2757 header field which is sent back to clients includes a
2758 description of the generic OS-type of the server as well as
2759 information about compiled-in modules.</p>
2762 <dt><code>ServerTokens Prod[uctOnly]</code></dt>
2764 <dd>Server sends (<em>e.g.</em>): <code>Server:
2767 <dt><code>ServerTokens Major</code></dt>
2769 <dd>Server sends (<em>e.g.</em>): <code>Server:
2770 Apache/2</code></dd>
2772 <dt><code>ServerTokens Minor</code></dt>
2774 <dd>Server sends (<em>e.g.</em>): <code>Server:
2775 Apache/2.0</code></dd>
2777 <dt><code>ServerTokens Min[imal]</code></dt>
2779 <dd>Server sends (<em>e.g.</em>): <code>Server:
2780 Apache/2.0.41</code></dd>
2782 <dt><code>ServerTokens OS</code></dt>
2784 <dd>Server sends (<em>e.g.</em>): <code>Server: Apache/2.0.41
2787 <dt><code>ServerTokens Full</code> (or not specified)</dt>
2789 <dd>Server sends (<em>e.g.</em>): <code>Server: Apache/2.0.41
2790 (Unix) PHP/4.2.2 MyMod/1.2</code></dd>
2793 <p>This setting applies to the entire server, and cannot be
2794 enabled or disabled on a virtualhost-by-virtualhost basis.</p>
2796 <p>After version 2.0.44, this directive also controls the
2797 information presented by the <directive
2798 module="core">ServerSignature</directive> directive.</p>
2800 <seealso><directive module="core">ServerSignature</directive></seealso>
2801 </directivesynopsis>
2804 <name>SetHandler</name>
2805 <description>Forces all matching files to be processed by a
2806 handler</description>
2807 <syntax>SetHandler <var>handler-name</var>|None</syntax>
2808 <contextlist><context>server config</context><context>virtual host</context>
2809 <context>directory</context><context>.htaccess</context>
2811 <override>FileInfo</override>
2812 <compatibility>Moved into the core in Apache 2.0</compatibility>
2815 <p>When placed into an <code>.htaccess</code> file or a
2816 <directive type="section" module="core">Directory</directive> or
2817 <directive type="section" module="core">Location</directive>
2818 section, this directive forces all matching files to be parsed
2819 through the <a href="../handler.html">handler</a> given by
2820 <var>handler-name</var>. For example, if you had a directory you
2821 wanted to be parsed entirely as imagemap rule files, regardless
2822 of extension, you might put the following into an
2823 <code>.htaccess</code> file in that directory:</p>
2826 SetHandler imap-file
2829 <p>Another example: if you wanted to have the server display a
2830 status report whenever a URL of
2831 <code>http://servername/status</code> was called, you might put
2832 the following into <code>httpd.conf</code>:</p>
2835 <Location /status><br />
2837 SetHandler server-status<br />
2842 <p>You can override an earlier defined <directive>SetHandler</directive>
2843 directive by using the value <code>None</code>.</p>
2846 <seealso><directive module="mod_mime">AddHandler</directive></seealso>
2848 </directivesynopsis>
2851 <name>SetInputFilter</name>
2852 <description>Sets the filters that will process client requests and POST
2854 <syntax>SetInputFilter <var>filter</var>[;<var>filter</var>...]</syntax>
2855 <contextlist><context>server config</context><context>virtual host</context>
2856 <context>directory</context><context>.htaccess</context>
2858 <override>FileInfo</override>
2861 <p>The <directive>SetInputFilter</directive> directive sets the
2862 filter or filters which will process client requests and POST
2863 input when they are received by the server. This is in addition to
2864 any filters defined elsewhere, including the
2865 <directive module="mod_mime">AddInputFilter</directive>
2868 <p>If more than one filter is specified, they must be separated
2869 by semicolons in the order in which they should process the
2872 <seealso><a href="../filter.html">Filters</a> documentation</seealso>
2873 </directivesynopsis>
2876 <name>SetOutputFilter</name>
2877 <description>Sets the filters that will process responses from the
2878 server</description>
2879 <syntax>SetOutputFilter <var>filter</var>[;<var>filter</var>...]</syntax>
2880 <contextlist><context>server config</context><context>virtual host</context>
2881 <context>directory</context><context>.htaccess</context>
2883 <override>FileInfo</override>
2886 <p>The <directive>SetOutputFilter</directive> directive sets the filters
2887 which will process responses from the server before they are
2888 sent to the client. This is in addition to any filters defined
2889 elsewhere, including the
2890 <directive module="mod_mime">AddOutputFilter</directive>
2893 <p>For example, the following configuration will process all files
2894 in the <code>/www/data/</code> directory for server-side
2898 <Directory /www/data/><br />
2900 SetOutputFilter INCLUDES<br />
2905 <p>If more than one filter is specified, they must be separated
2906 by semicolons in the order in which they should process the
2909 <seealso><a href="../filter.html">Filters</a> documentation</seealso>
2910 </directivesynopsis>
2913 <name>TimeOut</name>
2914 <description>Amount of time the server will wait for
2915 certain events before failing a request</description>
2916 <syntax>TimeOut <var>seconds</var></syntax>
2917 <default>TimeOut 300</default>
2918 <contextlist><context>server config</context></contextlist>
2921 <p>The <directive>TimeOut</directive> directive currently defines
2922 the amount of time Apache will wait for three things:</p>
2925 <li>The total amount of time it takes to receive a GET
2928 <li>The amount of time between receipt of TCP packets on a
2929 POST or PUT request.</li>
2931 <li>The amount of time between ACKs on transmissions of TCP
2932 packets in responses.</li>
2935 <p>We plan on making these separately configurable at some point
2936 down the road. The timer used to default to 1200 before 1.2,
2937 but has been lowered to 300 which is still far more than
2938 necessary in most situations. It is not set any lower by
2939 default because there may still be odd places in the code where
2940 the timer is not reset when a packet is sent. </p>
2942 </directivesynopsis>
2945 <name>UseCanonicalName</name>
2946 <description>Configures how the server determines its own name and
2948 <syntax>UseCanonicalName On|Off|DNS</syntax>
2949 <default>UseCanonicalName On</default>
2950 <contextlist><context>server config</context><context>virtual host</context>
2951 <context>directory</context></contextlist>
2954 <p>In many situations Apache must construct a <em>self-referential</em>
2955 URL -- that is, a URL that refers back to the same server. With
2956 <code>UseCanonicalName On</code> Apache will use the hostname and port
2957 specified in the <directive module="core">ServerName</directive>
2958 directive to construct the canonical name for the server. This name
2959 is used in all self-referential URLs, and for the values of
2960 <code>SERVER_NAME</code> and <code>SERVER_PORT</code> in CGIs.</p>
2962 <p>With <code>UseCanonicalName Off</code> Apache will form
2963 self-referential URLs using the hostname and port supplied by
2964 the client if any are supplied (otherwise it will use the
2965 canonical name, as defined above). These values are the same
2966 that are used to implement <a
2967 href="../vhosts/name-based.html">name based virtual hosts</a>,
2968 and are available with the same clients. The CGI variables
2969 <code>SERVER_NAME</code> and <code>SERVER_PORT</code> will be
2970 constructed from the client supplied values as well.</p>
2972 <p>An example where this may be useful is on an intranet server
2973 where you have users connecting to the machine using short
2974 names such as <code>www</code>. You'll notice that if the users
2975 type a shortname, and a URL which is a directory, such as
2976 <code>http://www/splat</code>, <em>without the trailing
2977 slash</em> then Apache will redirect them to
2978 <code>http://www.domain.com/splat/</code>. If you have
2979 authentication enabled, this will cause the user to have to
2980 authenticate twice (once for <code>www</code> and once again
2981 for <code>www.domain.com</code> -- see <a
2982 href="http://httpd.apache.org/docs/misc/FAQ.html#prompted-twice">the
2983 FAQ on this subject for more information</a>). But if
2984 <directive>UseCanonicalName</directive> is set <code>Off</code>, then
2985 Apache will redirect to <code>http://www/splat/</code>.</p>
2987 <p>There is a third option, <code>UseCanonicalName DNS</code>,
2988 which is intended for use with mass IP-based virtual hosting to
2989 support ancient clients that do not provide a
2990 <code>Host:</code> header. With this option Apache does a
2991 reverse DNS lookup on the server IP address that the client
2992 connected to in order to work out self-referential URLs.</p>
2994 <note type="warning"><title>Warning</title>
2995 <p>If CGIs make assumptions about the values of <code>SERVER_NAME</code>
2996 they may be broken by this option. The client is essentially free
2997 to give whatever value they want as a hostname. But if the CGI is
2998 only using <code>SERVER_NAME</code> to construct self-referential URLs
2999 then it should be just fine.</p>
3002 <seealso><directive module="core">ServerName</directive></seealso>
3003 <seealso><directive module="mpm_common">Listen</directive></seealso>
3004 </directivesynopsis>
3006 <directivesynopsis type="section">
3007 <name>VirtualHost</name>
3008 <description>Contains directives that apply only to a specific
3009 hostname or IP address</description>
3010 <syntax><VirtualHost
3011 <var>addr</var>[:<var>port</var>] [<var>addr</var>[:<var>port</var>]]
3012 ...> ... </VirtualHost></syntax>
3013 <contextlist><context>server config</context></contextlist>
3016 <p><directive type="section">VirtualHost</directive> and
3017 <code></VirtualHost></code> are used to enclose a group of
3018 directives that will apply only to a particular virtual host. Any
3019 directive that is allowed in a virtual host context may be
3020 used. When the server receives a request for a document on a
3021 particular virtual host, it uses the configuration directives
3022 enclosed in the <directive type="section">VirtualHost</directive>
3023 section. <var>Addr</var> can be:</p>
3026 <li>The IP address of the virtual host;</li>
3028 <li>A fully qualified domain name for the IP address of the
3031 <li>The character <code>*</code>, which is used only in combination with
3032 <code>NameVirtualHost *</code> to match all IP addresses; or</li>
3034 <li>The string <code>_default_</code>, which is used only
3035 with IP virtual hosting to catch unmatched IP addresses.</li>
3038 <example><title>Example</title>
3039 <VirtualHost 10.1.2.3><br />
3041 ServerAdmin webmaster@host.foo.com<br />
3042 DocumentRoot /www/docs/host.foo.com<br />
3043 ServerName host.foo.com<br />
3044 ErrorLog logs/host.foo.com-error_log<br />
3045 TransferLog logs/host.foo.com-access_log<br />
3047 </VirtualHost>
3051 <p>IPv6 addresses must be specified in square brackets because
3052 the optional port number could not be determined otherwise. An
3053 IPv6 example is shown below:</p>
3056 <VirtualHost [fe80::a00:20ff:fea7:ccea]><br />
3058 ServerAdmin webmaster@host.example.com<br />
3059 DocumentRoot /www/docs/host.example.com<br />
3060 ServerName host.example.com<br />
3061 ErrorLog logs/host.example.com-error_log<br />
3062 TransferLog logs/host.example.com-access_log<br />
3064 </VirtualHost>
3067 <p>Each Virtual Host must correspond to a different IP address,
3068 different port number or a different host name for the server,
3069 in the former case the server machine must be configured to
3070 accept IP packets for multiple addresses. (If the machine does
3071 not have multiple network interfaces, then this can be
3072 accomplished with the <code>ifconfig alias</code> command -- if
3073 your OS supports it).</p>
3075 <note><title>Note</title>
3076 <p>The use of <directive type="section">VirtualHost</directive> does
3077 <strong>not</strong> affect what addresses Apache listens on. You
3078 may need to ensure that Apache is listening on the correct addresses
3079 using <directive module="mpm_common">Listen</directive>.</p>
3082 <p>When using IP-based virtual hosting, the special name
3083 <code>_default_</code> can be specified in
3084 which case this virtual host will match any IP address that is
3085 not explicitly listed in another virtual host. In the absence
3086 of any <code>_default_</code> virtual host the "main" server config,
3087 consisting of all those definitions outside any VirtualHost
3088 section, is used when no IP-match occurs. (But note that any IP
3089 address that matches a <directive
3090 module="core">NameVirtualHost</directive> directive will use neither
3091 the "main" server config nor the <code>_default_</code> virtual host.
3092 See the <a href="../vhosts/name-based.html">name-based virtual hosting</a>
3093 documentation for further details.)</p>
3095 <p>You can specify a <code>:port</code> to change the port that is
3096 matched. If unspecified then it defaults to the same port as the
3097 most recent <directive module="mpm_common">Listen</directive>
3098 statement of the main server. You may also specify <code>:*</code>
3099 to match all ports on that address. (This is recommended when used
3100 with <code>_default_</code>.)</p>
3102 <note type="warning"><title>Security</title>
3103 <p>See the <a href="../misc/security_tips.html">security tips</a>
3104 document for details on why your security could be compromised if the
3105 directory where log files are stored is writable by anyone other
3106 than the user that starts the server.</p>
3109 <seealso><a href="../vhosts/">Apache Virtual Host documentation</a></seealso>
3110 <seealso><a href="../dns-caveats.html">Issues Regarding DNS and
3111 Apache</a></seealso>
3112 <seealso><a href="../bind.html">Setting
3113 which addresses and ports Apache uses</a></seealso>
3114 <seealso><a href="../sections.html">How <Directory>, <Location>
3115 and <Files> sections work</a> for an explanation of how these
3116 different sections are combined when a request is received</seealso>
3117 </directivesynopsis>