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<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="/faq/">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p>
<p class="apache">Apache HTTP Server Version 2.3</p>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a> > <a href="./">Modules</a></div>
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<div id="preamble"><h1>Apache Core Features</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="/de/mod/core.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
</div>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Core Apache HTTP Server features that are always
available</td></tr>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="/images/down.gif" /> <a href="#addoutputfilterbytype">AddOutputFilterByType</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#allowencodedslashes">AllowEncodedSlashes</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#limitinternalrecursion">LimitInternalRecursion</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#limitrequestfieldsize">LimitRequestFieldSize</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#limitxmlrequestbody">LimitXMLRequestBody</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#maxkeepaliverequests">MaxKeepAliveRequests</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#scriptinterpretersource">ScriptInterpreterSource</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></li>
</ul>
</div>
<div class="directive-section"><h2><a name="AcceptFilter" id="AcceptFilter">AcceptFilter</a> <a name="acceptfilter" id="acceptfilter">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures optimizations for a Protocol's Listener Sockets</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AcceptFilter <var>protocol</var> <var>accept_filter</var></code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.1.5 and later.
On Windows from Apache 2.3.3 and later.</td></tr>
</table>
<p>This directive enables operating system specific optimizations for a
listening socket by the Protocol type. The basic premise is for the
kernel to not send a socket to the server process until either data
is received or an entire HTTP Request is buffered. Only
FreeBSD's Accept Filters</a>, Linux's more primitive
<code>TCP_DEFER_ACCEPT</code>, and Windows' optimized AcceptEx()
are currently supported.</p>
<p>Using <code>none</code> for an argument will disable any accept filters
for that protocol. This is useful for protocols that require a server
send data first, such as <code>ftp:</code> or <code>nntp</code>:</p>
<div class="example"><p><code>AcceptFilter nntp none</code></p></div>
<p>The default values on FreeBSD are:</p>
<div class="example"><p><code>
AcceptFilter http httpready <br />
AcceptFilter https dataready
</code></p></div>
<p>The <code>httpready</code> accept filter buffers entire HTTP requests at
the kernel level. Once an entire request is received, the kernel then
sends it to the server. See the
accf_http(9)</a> man page for more details. Since HTTPS requests are
encrypted only the <a href="http://www.freebsd.org/cgi/man.cgi?query=accf_data&sektion=9">
accf_data(9)</a> filter is used.</p>
<p>The default values on Linux are:</p>
<div class="example"><p><code>
AcceptFilter http data <br />
AcceptFilter https data
</code></p></div>
<p>Linux's <code>TCP_DEFER_ACCEPT</code> does not support buffering http
requests. Any value besides <code>none</code> will enable
<code>TCP_DEFER_ACCEPT</code> on that listener. For more details
see the Linux
tcp(7)</a> man page.</p>
<p>The default values on Windows are:</p>
<div class="example"><p><code>
AcceptFilter http data <br />
AcceptFilter https data
</code></p></div>
<p>Window's mpm_winnt interprets the AcceptFilter to toggle the AcceptEx()
API, and does not support http protocol buffering. There are two values
which utilize the Windows AcceptEx() API and will recycle network
sockets between connections. <code>data</code> waits until data has
been transmitted as documented above, and the initial data buffer and
network endpoint addresses are all retrieved from the single AcceptEx()
invocation. <code>connect</code> will use the AcceptEx() API, also
retrieve the network endpoint addresses, but like <code>none</code>
the <code>connect</code> option does not wait for the initial data
transmission.</p>
<p>On Windows, <code>none</code> uses accept() rather than than AcceptEx()
and will not recycle sockets between connections. This is useful for
network adapters with broken driver support, as well as some virtual
network providers such as vpn drivers, or spam, virus or spyware
filters.</p>
</div>
<div class="directive-section"><h2><a name="AcceptPathInfo" id="AcceptPathInfo">AcceptPathInfo</a> <a name="acceptpathinfo" id="acceptpathinfo">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Resources accept trailing pathname information</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AcceptPathInfo On|Off|Default</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AcceptPathInfo Default</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.0.30 and later</td></tr>
</table>
<p>This directive controls whether requests that contain trailing
pathname information that follows an actual filename (or
non-existent file in an existing directory) will be accepted or
rejected. The trailing pathname information can be made
available to scripts in the <code>PATH_INFO</code> environment
variable.</p>
<p>For example, assume the location <code>/test/</code> points to
a directory that contains only the single file
<code>/more</code> as <code>PATH_INFO</code>.</p>
<p>The three possible arguments for the
<code class="directive">AcceptPathInfo</code> directive are:</p>
<dl>
<dt><code>Off</code></dt><dd>A request will only be accepted if it
maps to a literal path that exists. Therefore a request with
trailing pathname information after the true filename such as
a 404 NOT FOUND error.</dd>
<dt><code>On</code></dt><dd>A request will be accepted if a
leading path component maps to a file that exists. The above
<dt><code>Default</code></dt><dd>The treatment of requests with
trailing pathname information is determined by the <a href="/handler.html">handler</a> responsible for the request.
The core handler for normal files defaults to rejecting
<code>PATH_INFO</code> requests. Handlers that serve scripts, such as <a href="mod_cgi.html">cgi-script</a> and <a href="mod_isapi.html">isapi-handler</a>, generally accept
<code>PATH_INFO</code> by default.</dd>
</dl>
<p>The primary purpose of the <code>AcceptPathInfo</code>
directive is to allow you to override the handler's choice of
accepting or rejecting <code>PATH_INFO</code>. This override is required,
based on <code>PATH_INFO</code>. The core handler would usually reject
the request, so you can use the following configuration to enable
such a script:</p>
<div class="example"><p><code>
<Files "mypaths.shtml"><br />
<span class="indent">
Options +Includes<br />
SetOutputFilter INCLUDES<br />
AcceptPathInfo On<br />
</span>
</Files>
</code></p></div>
</div>
<div class="directive-section"><h2><a name="AccessFileName" id="AccessFileName">AccessFileName</a> <a name="accessfilename" id="accessfilename">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Name of the distributed configuration file</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AccessFileName <var>filename</var> [<var>filename</var>] ...</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AccessFileName .htaccess</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>While processing a request the server looks for
the first existing configuration file from this list of names in
every directory of the path to the document, if distributed
configuration files are <a href="#allowoverride">enabled for that
directory</a>. For example:</p>
<div class="example"><p><code>
AccessFileName .acl
</code></p></div>
<p>before returning the document
for directives, unless they have been disabled with</p>
<div class="example"><p><code>
<Directory /><br />
<span class="indent">
AllowOverride None<br />
</span>
</Directory>
</code></p></div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#allowoverride">AllowOverride</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="AddDefaultCharset" id="AddDefaultCharset">AddDefaultCharset</a> <a name="adddefaultcharset" id="adddefaultcharset">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default charset parameter to be added when a response
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AddDefaultCharset On|Off|<var>charset</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AddDefaultCharset Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>This directive specifies a default value for the media type
charset parameter (the name of a character encoding) to be added
to a response if and only if the response's content-type is either
any charset specified in the body of the response via a <code>META</code>
element, though the exact behavior is often dependent on the user's client
configuration. A setting of <code>AddDefaultCharset Off</code>
disables this functionality. <code>AddDefaultCharset On</code> enables
a default charset of <code>iso-8859-1</code>. Any other value is assumed
to be the <var>charset</var> to be used, which should be one of the
<a href="http://www.iana.org/assignments/character-sets">IANA registered
charset values</a> for use in Internet media types (MIME types).
For example:</p>
<div class="example"><p><code>
AddDefaultCharset utf-8
</code></p></div>
<p><code class="directive">AddDefaultCharset</code> should only be used when all
of the text resources to which it applies are known to be in that
character encoding and it is too inconvenient to label their charset
individually. One such example is to add the charset parameter
to resources containing generated content, such as legacy CGI
scripts, that might be vulnerable to cross-site scripting attacks
due to user-provided data being included in the output. Note, however,
that a better solution is to just fix (or delete) those scripts, since
setting a default charset does not protect users that have enabled
the "auto-detect character encoding" feature on their browser.</p>
<h3>See also</h3>
<ul>
</ul>
</div>
<div class="directive-section"><h2><a name="AddOutputFilterByType" id="AddOutputFilterByType">AddOutputFilterByType</a> <a name="addoutputfilterbytype" id="addoutputfilterbytype">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>assigns an output filter to a particular media-type</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AddOutputFilterByType <var>filter</var>[;<var>filter</var>...]
<var>media-type</var> [<var>media-type</var>] ...</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.0.33 and later; deprecated in Apache 2.1 and later</td></tr>
</table>
<p>This directive activates a particular output <a href="/filter.html">filter</a> for a request depending on the
response <a class="glossarylink" href="/glossary.html#media-type" title="see glossary">media-type</a>. Because of certain
problems discussed below, this directive is deprecated. The same
functionality is available using <code class="module"><a href="/mod/mod_filter.html">mod_filter</a></code>.</p>
<p>The following example uses the <code>DEFLATE</code> filter, which
is provided by <code class="module"><a href="/mod/mod_deflate.html">mod_deflate</a></code>. It will compress all
output (either static or dynamic) which is labeled as
to the client.</p>
<div class="example"><p><code>
</code></p></div>
<p>If you want the content to be processed by more than one filter, their
names have to be separated by semicolons. It's also possible to use one
<code class="directive">AddOutputFilterByType</code> directive for each of
these filters.</p>
<p>The configuration below causes all script output labeled as
<code>INCLUDES</code> filter and then by the <code>DEFLATE</code>
filter.</p>
<div class="example"><p><code>
<Location /cgi-bin/><br />
<span class="indent">
Options Includes<br />
</span>
</Location>
</code></p></div>
<div class="warning"><h3>Note</h3>
<p>Enabling filters with <code class="directive">AddOutputFilterByType</code>
may fail partially or completely in some cases. For example, no
filters are applied if the <a class="glossarylink" href="/glossary.html#media-type" title="see glossary">media-type</a> could not
be determined. If you want to make sure that the filters will be
applied, assign the content type to a resource explicitly; for
<code class="directive"><a href="#forcetype">ForceType</a></code>. Setting the
content type within a (non-nph) CGI script is also safe.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="/mod/mod_mime.html#addoutputfilter">AddOutputFilter</a></code></li>
<li><code class="directive"><a href="#setoutputfilter">SetOutputFilter</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="AllowEncodedSlashes" id="AllowEncodedSlashes">AllowEncodedSlashes</a> <a name="allowencodedslashes" id="allowencodedslashes">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determines whether encoded path separators in URLs are allowed to
be passed through</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AllowEncodedSlashes On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AllowEncodedSlashes Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.0.46 and later</td></tr>
</table>
<p>The <code class="directive">AllowEncodedSlashes</code> directive allows URLs
which contain encoded path separators (<code>%2F</code> for <code>/</code>
and additionally <code>%5C</code> for <code>\</code> on according systems)
to be used. Normally such URLs are refused with a 404 (Not found) error.</p>
<p>Turning <code class="directive">AllowEncodedSlashes</code> <code>On</code> is
mostly useful when used in conjunction with <code>PATH_INFO</code>.</p>
<div class="note"><h3>Note</h3>
<p>Allowing encoded slashes does <em>not</em> imply <em>decoding</em>.
Occurrences of <code>%2F</code> or <code>%5C</code> (<em>only</em> on
according systems) will be left as such in the otherwise decoded URL
string.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#acceptpathinfo">AcceptPathInfo</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="AllowOverride" id="AllowOverride">AllowOverride</a> <a name="allowoverride" id="allowoverride">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Types of directives that are allowed in
<code>.htaccess</code> files</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AllowOverride All|None|<var>directive-type</var>
[<var>directive-type</var>] ...</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AllowOverride All</code></td></tr>
</table>
<p>When the server finds an <code>.htaccess</code> file (as
specified by <code class="directive"><a href="#accessfilename">AccessFileName</a></code>)
it needs to know which directives declared in that file can override
earlier configuration directives.</p>
<div class="note"><h3>Only available in <Directory> sections</h3>
<code class="directive">AllowOverride</code> is valid only in
<code class="directive"><a href="#directory"><Directory></a></code>
sections specified without regular expressions, not in <code class="directive"><a href="#location"><Location></a></code>, <code class="directive"><a href="#directorymatch"><DirectoryMatch></a></code> or
<code class="directive"><a href="#files"><Files></a></code> sections.
</div>
<p>When this directive is set to <code>None</code>, then
<a href="#accessfilename">.htaccess</a> files are completely ignored.
In this case, the server will not even attempt to read
<code>.htaccess</code> files in the filesystem.</p>
<p>When this directive is set to <code>All</code>, then any
<code>.htaccess</code> files.</p>
<p>The <var>directive-type</var> can be one of the following
groupings of directives.</p>
<dl>
<dt>AuthConfig</dt>
<dd>
Allow use of the authorization directives (<code class="directive"><a href="/mod/mod_authn_dbm.html#authdbmgroupfile">AuthDBMGroupFile</a></code>,
<code class="directive"><a href="/mod/mod_authn_dbm.html#authdbmuserfile">AuthDBMUserFile</a></code>,
<code class="directive"><a href="/mod/mod_authz_groupfile.html#authgroupfile">AuthGroupFile</a></code>,
<code class="directive"><a href="/mod/mod_authn_core.html#authtype">AuthType</a></code>, <code class="directive"><a href="/mod/mod_authn_file.html#authuserfile">AuthUserFile</a></code>, <code class="directive"><a href="/mod/mod_authz_core.html#require">Require</a></code>, <em>etc.</em>).</dd>
<dt>FileInfo</dt>
<dd>
Allow use of the directives controlling document types
(<code class="directive"><a href="#errordocument">ErrorDocument</a></code>,
<code class="directive"><a href="#forcetype">ForceType</a></code>,
<code class="directive"><a href="/mod/mod_negotiation.html#languagepriority">LanguagePriority</a></code>,
<code class="directive"><a href="#sethandler">SetHandler</a></code>,
<code class="directive"><a href="#setinputfilter">SetInputFilter</a></code>,
<code class="directive"><a href="#setoutputfilter">SetOutputFilter</a></code>, and
document meta data (<code class="directive"><a href="/mod/mod_headers.html#header">Header</a></code>, <code class="directive"><a href="/mod/mod_headers.html#requestheader">RequestHeader</a></code>, <code class="directive"><a href="/mod/mod_setenvif.html#setenvif">SetEnvIf</a></code>, <code class="directive"><a href="/mod/mod_setenvif.html#setenvifnocase">SetEnvIfNoCase</a></code>, <code class="directive"><a href="/mod/mod_setenvif.html#browsermatch">BrowserMatch</a></code>, <code class="directive"><a href="/mod/mod_usertrack.html#cookieexpires">CookieExpires</a></code>, <code class="directive"><a href="/mod/mod_usertrack.html#cookiedomain">CookieDomain</a></code>, <code class="directive"><a href="/mod/mod_usertrack.html#cookiestyle">CookieStyle</a></code>, <code class="directive"><a href="/mod/mod_usertrack.html#cookietracking">CookieTracking</a></code>, <code class="directive"><a href="/mod/mod_usertrack.html#cookiename">CookieName</a></code>),
<code class="module"><a href="/mod/mod_rewrite.html">mod_rewrite</a></code> directives <code class="directive"><a href="/mod/mod_rewrite.html#rewriteengine">RewriteEngine</a></code>, <code class="directive"><a href="/mod/mod_rewrite.html#rewriteoptions">RewriteOptions</a></code>, <code class="directive"><a href="/mod/mod_rewrite.html#rewritebase">RewriteBase</a></code>, <code class="directive"><a href="/mod/mod_rewrite.html#rewritecond">RewriteCond</a></code>, <code class="directive"><a href="/mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>) and
</dd>
<dt>Indexes</dt>
<dd>
Allow use of the directives controlling directory indexing
(<code class="directive"><a href="/mod/mod_autoindex.html#adddescription">AddDescription</a></code>,
<code class="directive"><a href="/mod/mod_autoindex.html#addicon">AddIcon</a></code>, <code class="directive"><a href="/mod/mod_autoindex.html#addiconbyencoding">AddIconByEncoding</a></code>,
<code class="directive"><a href="/mod/mod_autoindex.html#defaulticon">DefaultIcon</a></code>, <code class="directive"><a href="/mod/mod_dir.html#directoryindex">DirectoryIndex</a></code>, <code class="directive"><a href="/mod/mod_autoindex.html#fancyindexing">FancyIndexing</a></code>, <code class="directive"><a href="/mod/mod_autoindex.html#headername">HeaderName</a></code>, <code class="directive"><a href="/mod/mod_autoindex.html#indexignore">IndexIgnore</a></code>, <code class="directive"><a href="/mod/mod_autoindex.html#indexoptions">IndexOptions</a></code>, <code class="directive"><a href="/mod/mod_autoindex.html#readmename">ReadmeName</a></code>,
<em>etc.</em>).</dd>
<dt>Limit</dt>
<dd>
Allow use of the directives controlling host access (<code class="directive"><a href="/mod/mod_authz_host.html#allow">Allow</a></code>, <code class="directive"><a href="/mod/mod_authz_host.html#deny">Deny</a></code> and <code class="directive"><a href="/mod/mod_authz_host.html#order">Order</a></code>).</dd>
<dt>Options[=<var>Option</var>,...]</dt>
<dd>
Allow use of the directives controlling specific directory
features (<code class="directive"><a href="#options">Options</a></code> and
An equal sign may be given followed by a comma (but no spaces)
separated lists of options that may be set using the <code class="directive"><a href="#options">Options</a></code> command.</dd>
</dl>
<p>Example:</p>
<div class="example"><p><code>
AllowOverride AuthConfig Indexes
</code></p></div>
<p>In the example above all directives that are neither in the group
<code>AuthConfig</code> nor <code>Indexes</code> cause an internal
server error.</p>
<div class="note"><p>For security and performance reasons, do not set
<code>AllowOverride</code> to anything other than <code>None</code>
in your <code><Directory /></code> block. Instead, find (or
create) the <code><Directory></code> block that refers to the
directory where you're actually planning to place a
<code>.htaccess</code> file.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#accessfilename">AccessFileName</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="CGIMapExtension" id="CGIMapExtension">CGIMapExtension</a> <a name="cgimapextension" id="cgimapextension">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Technique for locating the interpreter for CGI
scripts</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CGIMapExtension <var>cgi-path</var> <var>.extension</var></code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>NetWare only</td></tr>
</table>
<p>This directive is used to control how Apache finds the
interpreter used to run CGI scripts. For example, setting
cause all CGI script files with a <code>.foo</code> extension to
be passed to the FOO interpreter.</p>
</div>
<div class="directive-section"><h2><a name="ContentDigest" id="ContentDigest">ContentDigest</a> <a name="contentdigest" id="contentdigest">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables the generation of <code>Content-MD5</code> HTTP Response
headers</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ContentDigest On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ContentDigest Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>This directive enables the generation of
<code>Content-MD5</code> headers as defined in RFC1864
respectively RFC2616.</p>
<p>MD5 is an algorithm for computing a "message digest"
(sometimes called "fingerprint") of arbitrary-length data, with
a high degree of confidence that any alterations in the data
will be reflected in alterations in the message digest.</p>
<p>The <code>Content-MD5</code> header provides an end-to-end
message integrity check (MIC) of the entity-body. A proxy or
client may check this header for detecting accidental
modification of the entity-body in transit. Example header:</p>
<div class="example"><p><code>
Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==
</code></p></div>
<p>Note that this can cause performance problems on your server
since the message digest is computed on every request (the
values are not cached).</p>
<p><code>Content-MD5</code> is only sent for documents served
by the <code class="module"><a href="/mod/core.html">core</a></code>, and not by any module. For example,
SSI documents, output from CGI scripts, and byte range responses
do not have this header.</p>
</div>
<div class="directive-section"><h2><a name="DefaultType" id="DefaultType">DefaultType</a> <a name="defaulttype" id="defaulttype">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>This directive has no effect other than to emit warnings
if the value is not <code>none</code>. In prior versions, DefaultType
would specify a default media type to assign to response content for
which no other media type configuration could be found.
</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DefaultType <var>media-type|none</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DefaultType none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The argument <code>none</code> is available in Apache 2.2.7 and later. All other choices are DISABLED for 2.3.x and later.</td></tr>
</table>
<p>This directive has been disabled. For backwards compatibility
of configuration files, it may be specified with the value
<code>none</code>, meaning no default media type. For example:</p>
<div class="example"><p><code>
DefaultType None
</code></p></div>
<p><code>DefaultType None</code> is only available in
httpd-2.2.7 and later.</p>
<p>Use the mime.types configuration file and the
type assignments via file extensions, or the
<code class="directive"><a href="#forcetype">ForceType</a></code> directive to configure
the media type for specific resources. Otherwise, the server will
send the response without a Content-Type header field and the
recipient may attempt to guess the media type.</p>
</div>
<div class="directive-section"><h2><a name="Define" id="Define">Define</a> <a name="define" id="define">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Define the existence of a variable</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Define <var>parameter-name</var></code></td></tr>
</table>
<p>Equivalent to passing the <code>-D</code> argument to <code class="program"><a href="/programs/httpd.html">httpd</a></code>.</p>
<p>This directive can be used to toggle the use of <code class="directive"><a href="#ifdefine"><IfDefine></a></code> sections without needing to alter
<code>-D</code> arguments in any startup scripts.</p>
</div>
<div class="directive-section"><h2><a name="Directory" id="Directory"><Directory></a> <a name="directory" id="directory">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enclose a group of directives that apply only to the
named file-system directory and sub-directories</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><Directory <var>directory-path</var>>
... </Directory></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p><code class="directive"><Directory></code> and
<code></Directory></code> are used to enclose a group of
directives that will apply only to the named directory and
sub-directories of that directory. Any directive that is allowed
in a directory context may be used. <var>Directory-path</var> is
either the full path to a directory, or a wild-card string using
Unix shell-style matching. In a wild-card string, <code>?</code> matches
any single character, and <code>*</code> matches any sequences of
characters. You may also use <code>[]</code> character ranges. None
of the wildcards match a `/' character, so <code><Directory
/*/public_html></code> will not match
/home/*/public_html></code> will match. Example:</p>
<div class="example"><p><code>
<span class="indent">
Options Indexes FollowSymLinks<br />
</span>
</Directory>
</code></p></div>
<div class="note">
<p>Be careful with the <var>directory-path</var> arguments:
They have to literally match the filesystem path which Apache uses
to access the files. Directives applied to a particular
<code><Directory></code> will not apply to files accessed from
that same directory via a different path, such as via different symbolic
links.</p>
</div>
expressions</a> can also be used, with the addition of the
<code>~</code> character. For example:</p>
<div class="example"><p><code>
<Directory ~ "^/www/.*/[0-9]{3}">
</code></p></div>
<p>would match directories in <code>/www/</code> that consisted of
three numbers.</p>
<p>If multiple (non-regular expression) <code class="directive"><Directory></code> sections
match the directory (or one of its parents) containing a document,
then the directives are applied in the order of shortest match
first, interspersed with the directives from the <a href="#accessfilename">.htaccess</a> files. For example,
with</p>
<div class="example"><p><code>
<Directory /><br />
<span class="indent">
AllowOverride None<br />
</span>
</Directory><br />
<br />
<Directory /home/><br />
<span class="indent">
AllowOverride FileInfo<br />
</span>
</Directory>
</code></p></div>
the steps are:</p>
<ul>
<li>Apply directive <code>AllowOverride None</code>
(disabling <code>.htaccess</code> files).</li>
<li>Apply directive <code>AllowOverride FileInfo</code> (for
directory <code>/home</code>).</li>
<li>Apply any <code>FileInfo</code> directives in
</ul>
<p>Regular expressions are not considered until after all of the
normal sections have been applied. Then all of the regular
expressions are tested in the order they appeared in the
configuration file. For example, with</p>
<div class="example"><p><code>
<Directory ~ abc$><br />
<span class="indent">
# ... directives here ...<br />
</span>
</Directory>
</code></p></div>
<p>the regular expression section won't be considered until after
all normal <code class="directive"><Directory></code>s and
<code>.htaccess</code> files have been applied. Then the regular
the corresponding <code class="directive"><Directory></code> will
be applied.</p>
<p><strong>Note that the default Apache access for
<code><Directory /></code> is <code>Allow from All</code>.
This means that Apache will serve any file mapped from an URL. It is
recommended that you change this with a block such
as</strong></p>
<div class="example"><p><code>
<Directory /><br />
<span class="indent">
Order Deny,Allow<br />
Deny from All<br />
</span>
</Directory>
</code></p></div>
<p><strong>and then override this for directories you
<em>want</em> accessible. See the <a href="/misc/security_tips.html">Security Tips</a> page for more
details.</strong></p>
<code class="directive"><Directory></code> directives
cannot nest, and cannot appear in a <code class="directive"><a href="#limit"><Limit></a></code> or <code class="directive"><a href="#limitexcept"><LimitExcept></a></code> section.</p>
<h3>See also</h3>
<ul>
<Location> and <Files> sections work</a> for an
explanation of how these different sections are combined when a
request is received</li>
</ul>
</div>
<div class="directive-section"><h2><a name="DirectoryMatch" id="DirectoryMatch"><DirectoryMatch></a> <a name="directorymatch" id="directorymatch">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enclose directives that apply to
file-system directories matching a regular expression and their
subdirectories</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><DirectoryMatch <var>regex</var>>
... </DirectoryMatch></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p><code class="directive"><DirectoryMatch></code> and
<code></DirectoryMatch></code> are used to enclose a group
of directives which will apply only to the named directory and
sub-directories of that directory, the same as <code class="directive"><a href="#directory"><Directory></a></code>. However, it
takes as an argument a <a class="glossarylink" href="/glossary.html#regex" title="see glossary">regular
expression</a>. For example:</p>
<div class="example"><p><code>
<DirectoryMatch "^/www/(.+/)?[0-9]{3}">
</code></p></div>
<p>would match directories in <code>/www/</code> that consisted of three
numbers.</p>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#directory"><Directory></a></code> for
a description of how regular expressions are mixed in with normal
<code class="directive"><Directory></code>s</li>
<Files> sections work</a> for an explanation of how these different
sections are combined when a request is received</li>
</ul>
</div>
<div class="directive-section"><h2><a name="DocumentRoot" id="DocumentRoot">DocumentRoot</a> <a name="documentroot" id="documentroot">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory that forms the main document tree visible
from the web</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DocumentRoot <var>directory-path</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DocumentRoot /usr/local/apache/htdocs</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>This directive sets the directory from which <code class="program"><a href="/programs/httpd.html">httpd</a></code>
will serve files. Unless matched by a directive like <code class="directive"><a href="/mod/mod_alias.html#alias">Alias</a></code>, the server appends the
path from the requested URL to the document root to make the
path to the document. Example:</p>
<div class="example"><p><code>
</code></p></div>
<p>then an access to
not absolute then it is assumed to be relative to the <code class="directive"><a href="#serverroot">ServerRoot</a></code>.</p>
<p>The <code class="directive">DocumentRoot</code> should be specified without
a trailing slash.</p>
<h3>See also</h3>
<ul>
Locations</a></li>
</ul>
</div>
<div class="directive-section"><h2><a name="EnableMMAP" id="EnableMMAP">EnableMMAP</a> <a name="enablemmap" id="enablemmap">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Use memory-mapping to read files during delivery</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableMMAP On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableMMAP On</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>This directive controls whether the <code class="program"><a href="/programs/httpd.html">httpd</a></code> may use
memory-mapping if it needs to read the contents of a file during
delivery. By default, when the handling of a request requires
access to the data within a file -- for example, when delivering a
server-parsed file using <code class="module"><a href="/mod/mod_include.html">mod_include</a></code> -- Apache
memory-maps the file if the OS supports it.</p>
<p>This memory-mapping sometimes yields a performance improvement.
But in some environments, it is better to disable the memory-mapping
to prevent operational problems:</p>
<ul>
<li>On some multiprocessor systems, memory-mapping can reduce the
<li>Deleting or truncating a file while <code class="program"><a href="/programs/httpd.html">httpd</a></code>
has it memory-mapped can cause <code class="program"><a href="/programs/httpd.html">httpd</a></code> to
crash with a segmentation fault.
</li>
</ul>
<p>For server configurations that are vulnerable to these problems,
you should disable memory-mapping of delivered files by specifying:</p>
<div class="example"><p><code>
EnableMMAP Off
</code></p></div>
<p>For NFS mounted files, this feature may be disabled explicitly for
the offending files by specifying:</p>
<div class="example"><p><code>
<Directory "/path-to-nfs-files">
<span class="indent">
EnableMMAP Off
</span>
</Directory>
</code></p></div>
</div>
<div class="directive-section"><h2><a name="EnableSendfile" id="EnableSendfile">EnableSendfile</a> <a name="enablesendfile" id="enablesendfile">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Use the kernel sendfile support to deliver files to the client</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableSendfile On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableSendfile On</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.44 and later</td></tr>
</table>
<p>This directive controls whether <code class="program"><a href="/programs/httpd.html">httpd</a></code> may use the
sendfile support from the kernel to transmit file contents to the client.
By default, when the handling of a request requires no access
to the data within a file -- for example, when delivering a
static file -- Apache uses sendfile to deliver the file contents
without ever reading the file if the OS supports it.</p>
<p>This sendfile mechanism avoids separate read and send operations,
and buffer allocations. But on some platforms or within some
filesystems, it is better to disable this feature to avoid
operational problems:</p>
<ul>
<li>Some platforms may have broken sendfile support that the build
system did not detect, especially if the binaries were built on
another box and moved to such a machine with broken sendfile
support.</li>
<li>On Linux the use of sendfile triggers TCP-checksum
offloading bugs on certain networking cards when using IPv6.</li>
<li>On Linux on Itanium, sendfile may be unable to handle files
over 2GB in size.</li>
<li>With a network-mounted <code class="directive"><a href="#documentroot">DocumentRoot</a></code> (e.g., NFS or SMB),
the kernel may be unable to serve the network file through
its own cache.</li>
</ul>
<p>For server configurations that are vulnerable to these problems,
you should disable this feature by specifying:</p>
<div class="example"><p><code>
EnableSendfile Off
</code></p></div>
<p>For NFS or SMB mounted files, this feature may be disabled explicitly
for the offending files by specifying:</p>
<div class="example"><p><code>
<Directory "/path-to-nfs-files">
<span class="indent">
EnableSendfile Off
</span>
</Directory>
</code></p></div>
<p>Please note that the per-directory and .htaccess configuration
of <code class="directive">EnableSendfile</code> is not supported by
Only global definition of <code class="directive">EnableSendfile</code>
is taken into account by the module.
</p>
</div>
<div class="directive-section"><h2><a name="ErrorDocument" id="ErrorDocument">ErrorDocument</a> <a name="errordocument" id="errordocument">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>What the server will return to the client
in case of an error</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ErrorDocument <var>error-code</var> <var>document</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Quoting syntax for text messages is different in Apache
2.0</td></tr>
</table>
<p>In the event of a problem or error, Apache can be configured
to do one of four things,</p>
<ol>
<li>output a simple hardcoded error message</li>
<li>output a customized message</li>
<li>redirect to a local <var>URL-path</var> to handle the
<li>redirect to an external <var>URL</var> to handle the
</ol>
<p>The first option is the default, while options 2-4 are
configured using the <code class="directive">ErrorDocument</code>
directive, which is followed by the HTTP response code and a URL
or a message. Apache will sometimes offer additional information
<p>URLs can begin with a slash (/) for local web-paths (relative
to the <code class="directive"><a href="#documentroot">DocumentRoot</a></code>), or be a
full URL which the client can resolve. Alternatively, a message
can be provided to be displayed by the browser. Examples:</p>
<div class="example"><p><code>
ErrorDocument 500 http://foo.example.com/cgi-bin/tester<br />
ErrorDocument 401 /subscription_info.html<br />
ErrorDocument 403 "Sorry can't allow you access today"
</code></p></div>
<p>Additionally, the special value <code>default</code> can be used
to specify Apache's simple hardcoded message. While not required
under normal circumstances, <code>default</code> will restore
Apache's simple hardcoded message for configurations that would
otherwise inherit an existing <code class="directive">ErrorDocument</code>.</p>
<div class="example"><p><code>
<span class="indent">
ErrorDocument 404 default<br />
</span>
</Directory>
</code></p></div>
<p>Note that when you specify an <code class="directive">ErrorDocument</code>
that points to a remote URL (ie. anything with a method such as
<code>http</code> in front of it), Apache will send a redirect to the
client to tell it where to find the document, even if the
document ends up being on the same server. This has several
implications, the most important being that the client will not
receive the original error status code, but instead will
receive a redirect status code. This in turn can confuse web
robots and other clients which try to determine if a URL is
valid using the status code. In addition, if you use a remote
URL in an <code>ErrorDocument 401</code>, the client will not
know to prompt the user for a password since it will not
receive the 401 status code. Therefore, <strong>if you use an
<code>ErrorDocument 401</code> directive then it must refer to a local
document.</strong></p>
<p>Microsoft Internet Explorer (MSIE) will by default ignore
server-generated error messages when they are "too small" and substitute
its own "friendly" error messages. The size threshold varies depending on
the type of error, but in general, if you make your error document
greater than 512 bytes, then MSIE will show the server-generated
error rather than masking it. More information is available in
Microsoft Knowledge Base article <a href="http://support.microsoft.com/default.aspx?scid=kb;en-us;Q294807">Q294807</a>.</p>
<p>Although most error messages can be overriden, there are certain
circumstances where the internal messages are used regardless of the
setting of <code class="directive"><a href="#errordocument">ErrorDocument</a></code>. In
particular, if a malformed request is detected, normal request processing
will be immediately halted and the internal error message returned.
This is necessary to guard against security problems caused by
bad requests.</p>
<p>Prior to version 2.0, messages were indicated by prefixing
them with a single unmatched double quote character.</p>
<h3>See also</h3>
<ul>
customizable responses</a></li>
</ul>
</div>
<div class="directive-section"><h2><a name="ErrorLog" id="ErrorLog">ErrorLog</a> <a name="errorlog" id="errorlog">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location where the server will log errors</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code> ErrorLog <var>file-path</var>|syslog[:<var>facility</var>]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ErrorLog logs/error_log (Unix) ErrorLog logs/error.log (Windows and OS/2)</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive">ErrorLog</code> directive sets the name of
the file to which the server will log any errors it encounters. If
the <var>file-path</var> is not absolute then it is assumed to be
relative to the <code class="directive"><a href="#serverroot">ServerRoot</a></code>.</p>
<div class="example"><h3>Example</h3><p><code>
</code></p></div>
<p>If the <var>file-path</var>
begins with a pipe (|) then it is assumed to be a command to spawn
to handle the error log.</p>
<div class="example"><h3>Example</h3><p><code>
</code></p></div>
<p>Using <code>syslog</code> instead of a filename enables logging
via syslogd(8) if the system supports it. The default is to use
syslog facility <code>local7</code>, but you can override this by
using the <code>syslog:<var>facility</var></code> syntax where
<var>facility</var> can be one of the names usually documented in
syslog(1).</p>
<div class="example"><h3>Example</h3><p><code>
ErrorLog syslog:user
</code></p></div>
document for details on why your security could be compromised
if the directory where log files are stored is writable by
anyone other than the user that starts the server.</p>
<div class="warning"><h3>Note</h3>
<p>When entering a file path on non-Unix platforms, care should be taken
to make sure that only forward slashed are used even though the platform
may allow the use of back slashes. In general it is a good idea to always
use forward slashes throughout the configuration files.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#loglevel">LogLevel</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="FileETag" id="FileETag">FileETag</a> <a name="fileetag" id="fileetag">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File attributes used to create the ETag
HTTP response header</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>FileETag <var>component</var> ...</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>FileETag INode MTime Size</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>
The <code class="directive">FileETag</code> directive configures the file
attributes that are used to create the <code>ETag</code> (entity
tag) response header field when the document is based on a file.
(The <code>ETag</code> value is used in cache management to save
network bandwidth.) In Apache 1.3.22 and earlier, the
<code>ETag</code> value was <em>always</em> formed
from the file's inode, size, and last-modified time (mtime). The
<code class="directive">FileETag</code> directive allows you to choose
which of these -- if any -- should be used. The recognized keywords are:
</p>
<dl>
<dt><strong>INode</strong></dt>
<dd>The file's i-node number will be included in the calculation</dd>
<dt><strong>MTime</strong></dt>
<dd>The date and time the file was last modified will be included</dd>
<dt><strong>Size</strong></dt>
<dd>The number of bytes in the file will be included</dd>
<dt><strong>All</strong></dt>
<dd>All available fields will be used. This is equivalent to:
<div class="example"><p><code>FileETag INode MTime Size</code></p></div></dd>
<dt><strong>None</strong></dt>
<dd>If a document is file-based, no <code>ETag</code> field will be
included in the response</dd>
</dl>
<p>The <code>INode</code>, <code>MTime</code>, and <code>Size</code>
keywords may be prefixed with either <code>+</code> or <code>-</code>,
which allow changes to be made to the default setting inherited
from a broader scope. Any keyword appearing without such a prefix
immediately and completely cancels the inherited setting.</p>
<p>If a directory's configuration includes
<code>FileETag INode MTime Size</code>, and a
subdirectory's includes <code>FileETag -INode</code>,
the setting for that subdirectory (which will be inherited by
any sub-subdirectories that don't override it) will be equivalent to
<code>FileETag MTime Size</code>.</p>
<div class="warning"><h3>Warning</h3>
Do not change the default for directories or locations that have WebDAV
enabled and use <code class="module"><a href="/mod/mod_dav_fs.html">mod_dav_fs</a></code> as a storage provider.
<code class="module"><a href="/mod/mod_dav_fs.html">mod_dav_fs</a></code> uses <code>INode MTime Size</code>
as a fixed format for <code>ETag</code> comparisons on conditional requests.
These conditional requests will break if the <code>ETag</code> format is
changed via <code class="directive">FileETag</code>.
</div>
</div>
<div class="directive-section"><h2><a name="Files" id="Files"><Files></a> <a name="files" id="files">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Contains directives that apply to matched
filenames</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><Files <var>filename</var>> ... </Files></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive"><Files></code> directive
limits the scope of the enclosed directives by filename. It is comparable
to the <code class="directive"><a href="#directory"><Directory></a></code>
and <code class="directive"><a href="#location"><Location></a></code>
directives. It should be matched with a <code></Files></code>
directive. The directives given within this section will be applied to
any object with a basename (last component of filename) matching the
specified filename. <code class="directive"><Files></code>
sections are processed in the order they appear in the
configuration file, after the <code class="directive"><a href="#directory"><Directory></a></code> sections and
<code>.htaccess</code> files are read, but before <code class="directive"><a href="#location"><Location></a></code> sections. Note
that <code class="directive"><Files></code> can be nested
inside <code class="directive"><a href="#directory"><Directory></a></code> sections to restrict the
portion of the filesystem they apply to.</p>
<p>The <var>filename</var> argument should include a filename, or
a wild-card string, where <code>?</code> matches any single character,
and <code>*</code> matches any sequences of characters.
can also be used, with the addition of the
<code>~</code> character. For example:</p>
<div class="example"><p><code>
<Files ~ "\.(gif|jpe?g|png)$">
</code></p></div>
<p>would match most common Internet graphics formats. <code class="directive"><a href="#filesmatch"><FilesMatch></a></code> is preferred,
however.</p>
<p>Note that unlike <code class="directive"><a href="#directory"><Directory></a></code> and <code class="directive"><a href="#location"><Location></a></code> sections, <code class="directive"><Files></code> sections can be used inside
<code>.htaccess</code> files. This allows users to control access to
their own files, at a file-by-file level.</p>
<h3>See also</h3>
<ul>
and <Files> sections work</a> for an explanation of how these
different sections are combined when a request is received</li>
</ul>
</div>
<div class="directive-section"><h2><a name="FilesMatch" id="FilesMatch"><FilesMatch></a> <a name="filesmatch" id="filesmatch">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Contains directives that apply to regular-expression matched
filenames</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><FilesMatch <var>regex</var>> ... </FilesMatch></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive"><FilesMatch></code> directive
limits the scope of the enclosed directives by filename, just as the
<code class="directive"><a href="#files"><Files></a></code> directive
does. However, it accepts a <a class="glossarylink" href="/glossary.html#regex" title="see glossary">regular
expression</a>. For example:</p>
<div class="example"><p><code>
<FilesMatch "\.(gif|jpe?g|png)$">
</code></p></div>
<p>would match most common Internet graphics formats.</p>
<h3>See also</h3>
<ul>
and <Files> sections work</a> for an explanation of how these
different sections are combined when a request is received</li>
</ul>
</div>
<div class="directive-section"><h2><a name="ForceType" id="ForceType">ForceType</a> <a name="forcetype" id="forcetype">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Forces all matching files to be served with the specified
media type in the HTTP Content-Type header field</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ForceType <var>media-type</var>|None</code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Moved to the core in Apache 2.0</td></tr>
</table>
<p>When placed into an <code>.htaccess</code> file or a
<code class="directive"><a href="#directory"><Directory></a></code>, or
<code class="directive"><a href="#location"><Location></a></code> or
<code class="directive"><a href="#files"><Files></a></code>
section, this directive forces all matching files to be served
with the content type identification given by
<var>media-type</var>. For example, if you had a directory full of
GIF files, but did not want to label them all with <code>.gif</code>,
you might want to use:</p>
<div class="example"><p><code>
</code></p></div>
<p>Note that this directive overrides other indirect media type
associations defined in mime.types or via the
<p>You can also override more general
<code class="directive">ForceType</code> settings
by using the value of <code>None</code>:</p>
<div class="example"><p><code>
<Location /images><br />
<span class="indent">
</span>
</Location><br />
<br />
# but normal mime-type associations here:<br />
<span class="indent">
ForceType None<br />
</span>
</Location>
</code></p></div>
</div>
<div class="directive-section"><h2><a name="HostnameLookups" id="HostnameLookups">HostnameLookups</a> <a name="hostnamelookups" id="hostnamelookups">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables DNS lookups on client IP addresses</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>HostnameLookups On|Off|Double</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>HostnameLookups Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
</table>
<p>This directive enables DNS lookups so that host names can be
The value <code>Double</code> refers to doing double-reverse
DNS lookup. That is, after a reverse lookup is performed, a forward
lookup is then performed on that result. At least one of the IP
addresses in the forward lookup must match the original
address. (In "tcpwrappers" terminology this is called
<code>PARANOID</code>.)</p>
<p>Regardless of the setting, when <code class="module"><a href="/mod/mod_authz_host.html">mod_authz_host</a></code> is
used for controlling access by hostname, a double reverse lookup
will be performed. This is necessary for security. Note that the
result of this double-reverse isn't generally available unless you
set <code>HostnameLookups Double</code>. For example, if only
<code>HostnameLookups On</code> and a request is made to an object
that is protected by hostname restrictions, regardless of whether
the double-reverse fails or not, CGIs will still be passed the
single-reverse result in <code>REMOTE_HOST</code>.</p>
<p>The default is <code>Off</code> in order to save the network
traffic for those sites that don't truly need the reverse
lookups done. It is also better for the end users because they
don't have to suffer the extra latency that a lookup entails.
Heavily loaded sites should leave this directive
<code>Off</code>, since DNS lookups can take considerable
amounts of time. The utility <code class="program"><a href="/programs/logresolve.html">logresolve</a></code>, compiled by
default to the <code>bin</code> subdirectory of your installation
directory, can be used to look up host names from logged IP addresses
offline.</p>
</div>
<div class="directive-section"><h2><a name="If" id="If"><If></a> <a name="if" id="if">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Contains directives that apply only if a condition is
satisfied by a request at runtime</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><If <var>expression</var>> ... </If></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive"><If></code> directive
evaluates an expression at runtime, and applies the enclosed
directives if and only if the expression evaluates to true.
For example:</p>
<div class="example"><p><code>
<If "$req{Host} = ''">
</code></p></div>
<p>You may compare the value of any variable in the request headers
($req), response headers ($resp) or environment ($env) in your
expression.</p>
<h3>See also</h3>
<ul>
<Files> sections work</a> for an explanation of how these
different sections are combined when a request is received.
<code class="directive"><If></code> has the same precedence
and usage as <code class="directive"><Files></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="IfDefine" id="IfDefine"><IfDefine></a> <a name="ifdefine" id="ifdefine">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Encloses directives that will be processed only
if a test is true at startup</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><IfDefine [!]<var>parameter-name</var>> ...
</IfDefine></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code><IfDefine <var>test</var>>...</IfDefine>
</code> section is used to mark directives that are conditional. The
directives within an <code class="directive"><IfDefine></code>
section are only processed if the <var>test</var> is true. If <var>
test</var> is false, everything between the start and end markers is
ignored.</p>
<p>The <var>test</var> in the <code class="directive"><IfDefine></code> section directive can be one of two forms:</p>
<ul>
<li><var>parameter-name</var></li>
<li><code>!</code><var>parameter-name</var></li>
</ul>
<p>In the former case, the directives between the start and end
markers are only processed if the parameter named
<var>parameter-name</var> is defined. The second format reverses
the test, and only processes the directives if
<var>parameter-name</var> is <strong>not</strong> defined.</p>
<p>The <var>parameter-name</var> argument is a define as given on the
<code class="program"><a href="/programs/httpd.html">httpd</a></code> command line via <code>-D<var>parameter</var>
</code> at the time the server was started or by the <code class="directive"><a href="#define">Define</a></code> directive.</p>
<p><code class="directive"><IfDefine></code> sections are
nest-able, which can be used to implement simple
multiple-parameter tests. Example:</p>
<div class="example"><p><code>
httpd -DReverseProxy -DUseCache -DMemCache ...<br />
<br />
# httpd.conf<br />
<IfDefine ReverseProxy><br />
<span class="indent">
<IfDefine UseCache><br />
<span class="indent">
<IfDefine MemCache><br />
<span class="indent">
</span>
</IfDefine><br />
<IfDefine !MemCache><br />
<span class="indent">
</span>
</IfDefine>
</span>
</IfDefine>
</span>
</IfDefine>
</code></p></div>
</div>
<div class="directive-section"><h2><a name="IfModule" id="IfModule"><IfModule></a> <a name="ifmodule" id="ifmodule">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Encloses directives that are processed conditional on the
presence or absence of a specific module</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><IfModule [!]<var>module-file</var>|<var>module-identifier</var>> ...
</IfModule></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Module identifiers are available in version 2.1 and
later.</td></tr>
</table>
<p>The <code><IfModule <var>test</var>>...</IfModule></code>
section is used to mark directives that are conditional on the presence of
a specific module. The directives within an <code class="directive"><IfModule></code> section are only processed if the <var>test</var>
is true. If <var>test</var> is false, everything between the start and
end markers is ignored.</p>
<p>The <var>test</var> in the <code class="directive"><IfModule></code> section directive can be one of two forms:</p>
<ul>
<li><var>module</var></li>
<li>!<var>module</var></li>
</ul>
<p>In the former case, the directives between the start and end
markers are only processed if the module named <var>module</var>
is included in Apache -- either compiled in or
dynamically loaded using <code class="directive"><a href="/mod/mod_so.html#loadmodule">LoadModule</a></code>. The second format reverses the test,
and only processes the directives if <var>module</var> is
<strong>not</strong> included.</p>
<p>The <var>module</var> argument can be either the module identifier or
the file name of the module, at the time it was compiled. For example,
<code>rewrite_module</code> is the identifier and
several source files, use the name of the file containing the string
<code>STANDARD20_MODULE_STUFF</code>.</p>
<p><code class="directive"><IfModule></code> sections are
nest-able, which can be used to implement simple multiple-module
tests.</p>
<div class="note">This section should only be used if you need to have one
configuration file that works whether or not a specific module
is available. In normal operation, directives need not be
placed in <code class="directive"><IfModule></code>
sections.</div>
</div>
<div class="directive-section"><h2><a name="Include" id="Include">Include</a> <a name="include" id="include">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Includes other configuration files from within
the server configuration files</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Include <var>file-path</var>|<var>directory-path</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Wildcard matching available in 2.0.41 and later</td></tr>
</table>
<p>This directive allows inclusion of other configuration files
from within the server configuration files.</p>
<p>Shell-style (<code>fnmatch()</code>) wildcard characters can be used to
include several files at once, in alphabetical order. In
addition, if <code class="directive">Include</code> points to a directory,
rather than a file, Apache will read all files in that directory
and any subdirectory. However, including entire directories is not
recommended, because it is easy to accidentally leave temporary
files in a directory that can cause <code class="program"><a href="/programs/httpd.html">httpd</a></code> to
fail. Instead, we encourage you to use the wildcard syntax shown
below, to include files that match a particular pattern, such as
*.conf, for example.</p>
<p>The file path specified may be an absolute path, or may be relative
to the <code class="directive"><a href="#serverroot">ServerRoot</a></code> directory.</p>
<p>Examples:</p>
<div class="example"><p><code>
</code></p></div>
<p>Or, providing paths relative to your <code class="directive"><a href="#serverroot">ServerRoot</a></code> directory:</p>
<div class="example"><p><code>
</code></p></div>
<h3>See also</h3>
<ul>
</ul>
</div>
<div class="directive-section"><h2><a name="KeepAlive" id="KeepAlive">KeepAlive</a> <a name="keepalive" id="keepalive">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables HTTP persistent connections</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>KeepAlive On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>KeepAlive On</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
which allow multiple requests to be sent over the same TCP
connection. In some cases this has been shown to result in an
almost 50% speedup in latency times for HTML documents with
many images. To enable Keep-Alive connections, set
<code>KeepAlive On</code>.</p>
used if they are specifically requested by a client. In
only be used when the length of the content is known in
advance. This implies that dynamic content such as CGI output,
SSI pages, and server-generated directory listings will
unless otherwise specified. If the client requests it, chunked
encoding will be used in order to send content of unknown
length over persistent connections.</p>
<p>When a client uses a Keep-Alive connection it will be counted
as a single "request" for the <code class="directive"><a href="/mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code> directive, regardless
of how many requests are sent using the connection.</p>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#maxkeepaliverequests">MaxKeepAliveRequests</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="KeepAliveTimeout" id="KeepAliveTimeout">KeepAliveTimeout</a> <a name="keepalivetimeout" id="keepalivetimeout">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Amount of time the server will wait for subsequent
requests on a persistent connection</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>KeepAliveTimeout <var>num</var>[ms]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>KeepAliveTimeout 5</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Specifying a value in milliseconds is available in
Apache 2.3.2 and later</td></tr>
</table>
<p>The number of seconds Apache will wait for a subsequent
request before closing the connection. By adding a postfix of ms the
timeout can be also set in milliseconds. Once a request has been
received, the timeout value specified by the
<code class="directive"><a href="#timeout">Timeout</a></code> directive applies.</p>
<p>Setting <code class="directive">KeepAliveTimeout</code> to a high value
may cause performance problems in heavily loaded servers. The
higher the timeout, the more server processes will be kept
occupied waiting on connections with idle clients.</p>
<p>In a name-based virtual host context, the value of the first
defined virtual host (the default host) in a set of <code class="directive"><a href="#namevirtualhost">NameVirtualHost</a></code> will be used.
The other values will be ignored.</p>
</div>
<div class="directive-section"><h2><a name="Limit" id="Limit"><Limit></a> <a name="limit" id="limit">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Restrict enclosed access controls to only certain HTTP
methods</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><Limit <var>method</var> [<var>method</var>] ... > ...
</Limit></code></td></tr>
</table>
<p>Access controls are normally effective for
<strong>all</strong> access methods, and this is the usual
desired behavior. <strong>In the general case, access control
directives should not be placed within a
<code class="directive"><Limit></code> section.</strong></p>
<p>The purpose of the <code class="directive"><Limit></code>
directive is to restrict the effect of the access controls to the
nominated HTTP methods. For all other methods, the access
restrictions that are enclosed in the <code class="directive"><Limit></code> bracket <strong>will have no
effect</strong>. The following example applies the access control
only to the methods <code>POST</code>, <code>PUT</code>, and
<code>DELETE</code>, leaving all other methods unprotected:</p>
<div class="example"><p><code>
<Limit POST PUT DELETE><br />
<span class="indent">
Require valid-user<br />
</span>
</Limit>
</code></p></div>
<p>The method names listed can be one or more of: <code>GET</code>,
<code>POST</code>, <code>PUT</code>, <code>DELETE</code>,
<code>CONNECT</code>, <code>OPTIONS</code>,
<code>PATCH</code>, <code>PROPFIND</code>, <code>PROPPATCH</code>,
<code>MKCOL</code>, <code>COPY</code>, <code>MOVE</code>,
<code>LOCK</code>, and <code>UNLOCK</code>. <strong>The method name is
case-sensitive.</strong> If <code>GET</code> is used it will also
restrict <code>HEAD</code> requests. The <code>TRACE</code> method
cannot be limited (see <code class="directive"><a href="#traceenable">TraceEnable</a></code>).</p>
<div class="warning">A <code class="directive"><a href="#limitexcept"><LimitExcept></a></code> section should always be
used in preference to a <code class="directive"><Limit></code>
section when restricting access, since a <code class="directive"><a href="#limitexcept"><LimitExcept></a></code> section provides protection
against arbitrary methods.</div>
<p>The <code class="directive"><Limit></code> and
<code class="directive"><a href="#limitexcept"><LimitExcept></a></code>
directives may be nested. In this case, each successive level of
<code class="directive"><Limit></code> or <code class="directive"><a href="#limitexcept"><LimitExcept></a></code> directives must
further restrict the set of methods to which access controls apply.</p>
<div class="warning">When using
<code class="directive"><Limit></code> or
<code class="directive"><LimitExcept></code> directives with
the <code class="directive"><a href="/mod/mod_authz_core.html#require">Require</a></code> directive,
note that the first <code class="directive"><a href="/mod/mod_authz_core.html#require">Require</a></code>
to succeed authorizes the request, regardless of the presence of other
<code class="directive"><a href="/mod/mod_authz_core.html#require">Require</a></code> directives.</div>
<p>For example, given the following configuration, all users will
be authorized for <code>POST</code> requests, and the
<code>Require group editors</code> directive will be ignored
in all cases:</p>
<div class="example"><p><code>
<LimitExcept GET>
<span class="indent">
Require valid-user
</span>
</LimitExcept><br />
<Limit POST>
<span class="indent">
Require group editors
</span>
</Limit>
</code></p></div>
</div>
<div class="directive-section"><h2><a name="LimitExcept" id="LimitExcept"><LimitExcept></a> <a name="limitexcept" id="limitexcept">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Restrict access controls to all HTTP methods
except the named ones</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code><LimitExcept <var>method</var> [<var>method</var>] ... > ...
</LimitExcept></code></td></tr>
</table>
<p><code class="directive"><LimitExcept></code> and
<code></LimitExcept></code> are used to enclose
a group of access control directives which will then apply to any
HTTP access method <strong>not</strong> listed in the arguments;
i.e., it is the opposite of a <code class="directive"><a href="#limit"><Limit></a></code> section and can be used to control
both standard and nonstandard/unrecognized methods. See the
documentation for <code class="directive"><a href="#limit"><Limit></a></code> for more details.</p>
<p>For example:</p>
<div class="example"><p><code>
<LimitExcept POST GET><br />
<span class="indent">
Require valid-user<br />
</span>
</LimitExcept>
</code></p></div>
</div>
<div class="directive-section"><h2><a name="LimitInternalRecursion" id="LimitInternalRecursion">LimitInternalRecursion</a> <a name="limitinternalrecursion" id="limitinternalrecursion">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determine maximum number of internal redirects and nested
subrequests</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitInternalRecursion <var>number</var> [<var>number</var>]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitInternalRecursion 10</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.0.47 and later</td></tr>
</table>
<p>An internal redirect happens, for example, when using the <code class="directive"><a href="/mod/mod_actions.html#action">Action</a></code> directive, which internally
redirects the original request to a CGI script. A subrequest is Apache's
mechanism to find out what would happen for some URI if it were requested.
For example, <code class="module"><a href="/mod/mod_dir.html">mod_dir</a></code> uses subrequests to look for the
files listed in the <code class="directive"><a href="/mod/mod_dir.html#directoryindex">DirectoryIndex</a></code>
directive.</p>
<p><code class="directive">LimitInternalRecursion</code> prevents the server
from crashing when entering an infinite loop of internal redirects or
subrequests. Such loops are usually caused by misconfigurations.</p>
<p>The directive stores two different limits, which are evaluated on
per-request basis. The first <var>number</var> is the maximum number of
internal redirects, that may follow each other. The second <var>number</var>
determines, how deep subrequests may be nested. If you specify only one
<var>number</var>, it will be assigned to both limits.</p>
<div class="example"><h3>Example</h3><p><code>
LimitInternalRecursion 5
</code></p></div>
</div>
<div class="directive-section"><h2><a name="LimitRequestBody" id="LimitRequestBody">LimitRequestBody</a> <a name="limitrequestbody" id="limitrequestbody">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Restricts the total size of the HTTP request body sent
from the client</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitRequestBody <var>bytes</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitRequestBody 0</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>This directive specifies the number of <var>bytes</var> from 0
(meaning unlimited) to 2147483647 (2GB) that are allowed in a
request body.</p>
<p>The <code class="directive">LimitRequestBody</code> directive allows
the user to set a limit on the allowed size of an HTTP request
message body within the context in which the directive is given
(server, per-directory, per-file or per-location). If the client
request exceeds that limit, the server will return an error
response instead of servicing the request. The size of a normal
request message body will vary greatly depending on the nature of
the resource and the methods allowed on that resource. CGI scripts
typically use the message body for retrieving form information.
Implementations of the <code>PUT</code> method will require
a value at least as large as any representation that the server
wishes to accept for that resource.</p>
<p>This directive gives the server administrator greater
control over abnormal client request behavior, which may be
useful for avoiding some forms of denial-of-service
attacks.</p>
<p>If, for example, you are permitting file upload to a particular
location, and wish to limit the size of the uploaded file to 100K,
you might use the following directive:</p>
<div class="example"><p><code>
LimitRequestBody 102400
</code></p></div>
</div>
<div class="directive-section"><h2><a name="LimitRequestFields" id="LimitRequestFields">LimitRequestFields</a> <a name="limitrequestfields" id="limitrequestfields">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the number of HTTP request header fields that
will be accepted from the client</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitRequestFields <var>number</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitRequestFields 100</code></td></tr>
</table>
<p><var>Number</var> is an integer from 0 (meaning unlimited) to
32767. The default value is defined by the compile-time
constant <code>DEFAULT_LIMIT_REQUEST_FIELDS</code> (100 as
distributed).</p>
<p>The <code class="directive">LimitRequestFields</code> directive allows
the server administrator to modify the limit on the number of
request header fields allowed in an HTTP request. A server needs
this value to be larger than the number of fields that a normal
client request might include. The number of request header fields
used by a client rarely exceeds 20, but this may vary among
different client implementations, often depending upon the extent
to which a user has configured their browser to support detailed
content negotiation. Optional HTTP extensions are often expressed
using request header fields.</p>
<p>This directive gives the server administrator greater
control over abnormal client request behavior, which may be
useful for avoiding some forms of denial-of-service attacks.
The value should be increased if normal clients see an error
response from the server that indicates too many fields were
sent in the request.</p>
<p>For example:</p>
<div class="example"><p><code>
LimitRequestFields 50
</code></p></div>
</div>
<div class="directive-section"><h2><a name="LimitRequestFieldSize" id="LimitRequestFieldSize">LimitRequestFieldSize</a> <a name="limitrequestfieldsize" id="limitrequestfieldsize">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the size of the HTTP request header allowed from the
client</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitRequestFieldSize <var>bytes</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitRequestFieldSize 8190</code></td></tr>
</table>
<p>This directive specifies the number of <var>bytes</var>
that will be allowed in an HTTP request header.</p>
<p>The <code class="directive">LimitRequestFieldSize</code> directive
allows the server administrator to reduce or increase the limit
on the allowed size of an HTTP request header field. A server
needs this value to be large enough to hold any one header field
from a normal client request. The size of a normal request header
field will vary greatly among different client implementations,
often depending upon the extent to which a user has configured
their browser to support detailed content negotiation. SPNEGO
authentication headers can be up to 12392 bytes.</p>
<p>This directive gives the server administrator greater
control over abnormal client request behavior, which may be
useful for avoiding some forms of denial-of-service attacks.</p>
<p>For example:</p>
<div class="example"><p><code>
LimitRequestFieldSize 4094
</code></p></div>
<div class="note">Under normal conditions, the value should not be changed from
the default.</div>
</div>
<div class="directive-section"><h2><a name="LimitRequestLine" id="LimitRequestLine">LimitRequestLine</a> <a name="limitrequestline" id="limitrequestline">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit the size of the HTTP request line that will be accepted
from the client</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitRequestLine <var>bytes</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitRequestLine 8190</code></td></tr>
</table>
<p>This directive sets the number of <var>bytes</var> that will be
allowed on the HTTP request-line.</p>
<p>The <code class="directive">LimitRequestLine</code> directive allows
the server administrator to reduce or increase the limit on the allowed size
of a client's HTTP request-line. Since the request-line consists of the
HTTP method, URI, and protocol version, the
<code class="directive">LimitRequestLine</code> directive places a
restriction on the length of a request-URI allowed for a request
on the server. A server needs this value to be large enough to
hold any of its resource names, including any information that
might be passed in the query part of a <code>GET</code> request.</p>
<p>This directive gives the server administrator greater
control over abnormal client request behavior, which may be
useful for avoiding some forms of denial-of-service attacks.</p>
<p>For example:</p>
<div class="example"><p><code>
LimitRequestLine 4094
</code></p></div>
<div class="note">Under normal conditions, the value should not be changed from
the default.</div>
</div>
<div class="directive-section"><h2><a name="LimitXMLRequestBody" id="LimitXMLRequestBody">LimitXMLRequestBody</a> <a name="limitxmlrequestbody" id="limitxmlrequestbody">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the size of an XML-based request body</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LimitXMLRequestBody <var>bytes</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LimitXMLRequestBody 1000000</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>Limit (in bytes) on maximum size of an XML-based request
body. A value of <code>0</code> will disable any checking.</p>
<p>Example:</p>
<div class="example"><p><code>
LimitXMLRequestBody 0
</code></p></div>
</div>
<div class="directive-section"><h2><a name="Location" id="Location"><Location></a> <a name="location" id="location">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Applies the enclosed directives only to matching
URLs</td></tr>
<var>URL-path</var>|<var>URL</var>> ... </Location></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive"><Location></code> directive
limits the scope of the enclosed directives by URL. It is similar to the
<code class="directive"><a href="#directory"><Directory></a></code>
directive, and starts a subsection which is terminated with a
<code></Location></code> directive. <code class="directive"><Location></code> sections are processed in the
order they appear in the configuration file, after the <code class="directive"><a href="#directory"><Directory></a></code> sections and
<code>.htaccess</code> files are read, and after the <code class="directive"><a href="#files"><Files></a></code> sections.</p>
<p><code class="directive"><Location></code> sections operate
completely outside the filesystem. This has several consequences.
Most importantly, <code class="directive"><Location></code>
directives should not be used to control access to filesystem
locations. Since several different URLs may map to the same
filesystem location, such access controls may by circumvented.</p>
<div class="note"><h3>When to use <code class="directive"><Location></code></h3>
<p>Use <code class="directive"><Location></code> to apply
directives to content that lives outside the filesystem. For
content that lives in the filesystem, use <code class="directive"><a href="#directory"><Directory></a></code> and <code class="directive"><a href="#files"><Files></a></code>. An exception is
<code><Location /></code>, which is an easy way to
apply a configuration to the entire server.</p>
</div>
<p>For all origin (non-proxy) requests, the URL to be matched is a
URL-path of the form <code>/path/</code>. <em>No scheme, hostname,
port, or query string may be included.</em> For proxy requests, the
URL to be matched is of the form
prefix.</p>
<p>The URL may use wildcards. In a wild-card string, <code>?</code> matches
any single character, and <code>*</code> matches any sequences of
characters. Neither wildcard character matches a / in the URL-path.</p>
can also be used, with the addition of the <code>~</code>
character. For example:</p>
<div class="example"><p><code>
<Location ~ "/(extra|special)/data">
</code></p></div>
or <code>/special/data</code>. The directive <code class="directive"><a href="#locationmatch"><LocationMatch></a></code> behaves
identical to the regex version of <code class="directive"><Location></code>, and is preferred, for the
simple reason that <code>~</code> is hard to distinguish from
<code>-</code> in many fonts.</p>
<p>The <code class="directive"><Location></code>
functionality is especially useful when combined with the
<code class="directive"><a href="#sethandler">SetHandler</a></code>
directive. For example, to enable status requests, but allow them
<div class="example"><p><code>
<Location /status><br />
<span class="indent">
SetHandler server-status<br />
Order Deny,Allow<br />
Deny from all<br />
Allow from .example.com<br />
</span>
</Location>
</code></p></div>
<div class="note"><h3>Note about / (slash)</h3>
<p>The slash character has special meaning depending on where in a
URL it appears. People may be used to its behavior in the filesystem
where multiple adjacent slashes are frequently collapsed to a single
The <code class="directive"><a href="#locationmatch"><LocationMatch></a></code>
directive and the regex version of <code class="directive"><Location></code> require you to explicitly specify multiple
slashes if that is your intention.</p>
<p>For example, <code><LocationMatch ^/abc></code> would match
the request URL <code>/abc</code> but not the request URL <code>
//abc</code>. The (non-regex) <code class="directive"><Location></code> directive behaves similarly when used for
proxy requests. But when (non-regex) <code class="directive"><Location></code> is used for non-proxy requests it will
implicitly match multiple slashes with a single slash. For example,
request is to <code>/abc//def</code> then it will match.</p>
</div>
<h3>See also</h3>
<ul>
and <Files> sections work</a> for an explanation of how these
different sections are combined when a request is received.</li>
<li><code class="directive"><a href="#locationmatch">LocationMatch</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="LocationMatch" id="LocationMatch"><LocationMatch></a> <a name="locationmatch" id="locationmatch">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Applies the enclosed directives only to regular-expression
matching URLs</td></tr>
<var>regex</var>> ... </LocationMatch></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive"><LocationMatch></code> directive
limits the scope of the enclosed directives by URL, in an identical manner
to <code class="directive"><a href="#location"><Location></a></code>. However,
it takes a <a class="glossarylink" href="/glossary.html#regex" title="see glossary">regular expression</a>
as an argument instead of a simple string. For example:</p>
<div class="example"><p><code>
<LocationMatch "/(extra|special)/data">
</code></p></div>
<h3>See also</h3>
<ul>
and <Files> sections work</a> for an explanation of how these
different sections are combined when a request is received</li>
</ul>
</div>
<div class="directive-section"><h2><a name="LogLevel" id="LogLevel">LogLevel</a> <a name="loglevel" id="loglevel">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Controls the verbosity of the ErrorLog</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LogLevel <var>level</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LogLevel warn</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p><code class="directive">LogLevel</code> adjusts the verbosity of the
messages recorded in the error logs (see <code class="directive"><a href="#errorlog">ErrorLog</a></code> directive). The following
<var>level</var>s are available, in order of decreasing
significance:</p>
<table class="bordered">
<tr>
<th><strong>Level</strong> </th>
<th><strong>Description</strong> </th>
<th><strong>Example</strong> </th>
</tr>
<tr>
<td><code>emerg</code> </td>
<td>Emergencies - system is unusable.</td>
<td>"Child cannot open lock file. Exiting"</td>
</tr>
<tr>
<td><code>alert</code> </td>
<td>Action must be taken immediately.</td>
<td>"getpwuid: couldn't determine user name from uid"</td>
</tr>
<tr>
<td><code>crit</code> </td>
<td>Critical Conditions.</td>
<td>"socket: Failed to get a socket, exiting child"</td>
</tr>
<tr>
<td><code>error</code> </td>
<td>Error conditions.</td>
<td>"Premature end of script headers"</td>
</tr>
<tr>
<td><code>warn</code> </td>
<td>Warning conditions.</td>
<td>"child process 1234 did not exit, sending another
SIGHUP"</td>
</tr>
<tr>
<td><code>notice</code> </td>
<td>Normal but significant condition.</td>
<td>"httpd: caught SIGBUS, attempting to dump core in
..."</td>
</tr>
<tr>
<td><code>info</code> </td>
<td>Informational.</td>
<td>"Server seems busy, (you may need to increase
</tr>
<tr>
<td><code>debug</code> </td>
<td>Debug-level messages</td>
<td>"Opening config file ..."</td>
</tr>
</table>
<p>When a particular level is specified, messages from all
other levels of higher significance will be reported as well.
then messages with log levels of <code>notice</code> and
<code>warn</code> will also be posted.</p>
<p>Using a level of at least <code>crit</code> is
recommended.</p>
<p>For example:</p>
<div class="example"><p><code>
LogLevel notice
</code></p></div>
<div class="note"><h3>Note</h3>
<p>When logging to a regular file messages of the level
<code>notice</code> cannot be suppressed and thus are always
logged. However, this doesn't apply when logging is done
using <code>syslog</code>.</p>
</div>
</div>
<div class="directive-section"><h2><a name="MaxKeepAliveRequests" id="MaxKeepAliveRequests">MaxKeepAliveRequests</a> <a name="maxkeepaliverequests" id="maxkeepaliverequests">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of requests allowed on a persistent
connection</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxKeepAliveRequests <var>number</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxKeepAliveRequests 100</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive">MaxKeepAliveRequests</code> directive
limits the number of requests allowed per connection when
<code class="directive"><a href="#keepalive">KeepAlive</a></code> is on. If it is
set to <code>0</code>, unlimited requests will be allowed. We
recommend that this setting be kept to a high value for maximum
server performance.</p>
<p>For example:</p>
<div class="example"><p><code>
MaxKeepAliveRequests 500
</code></p></div>
</div>
<div class="directive-section"><h2><a name="NameVirtualHost" id="NameVirtualHost">NameVirtualHost</a> <a name="namevirtualhost" id="namevirtualhost">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Designates an IP address for name-virtual
hosting</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>NameVirtualHost <var>addr</var>[:<var>port</var>]</code></td></tr>
</table>
<p>A single <code class="directive">NameVirtualHost</code> directive
identifies a set of identical virtual hosts on which the server will
further select from on the basis of the <em>hostname</em>
requested by the client. The <code class="directive">NameVirtualHost</code>
directive is a required directive if you want to configure
<p>This directive, and the corresponding <code class="directive">VirtualHost</code>,
<em>must</em> be qualified with a port number if the server supports both HTTP
and HTTPS connections.</p>
<p>Although <var>addr</var> can be a hostname, it is recommended
that you always use an IP address or a wildcard. A wildcard
NameVirtualHost matches only virtualhosts that also have a literal wildcard
as their argument.</p>
<p>In cases where a firewall or other proxy receives the requests and
forwards them on a different IP address to the server, you must specify the
IP address of the physical interface on the machine which will be
servicing the requests. </p>
<p> In the example below, requests received on interface 192.0.2.1 and port 80
will only select among the first two virtual hosts. Requests received on
port 80 on any other interface will only select among the third and fourth
virtual hosts. In the common case where the interface isn't important
to the mapping, only the "*:80" NameVirtualHost and VirtualHost directives
are necessary.</p>
<div class="example"><p><code>
NameVirtualHost 192.0.2.1:80<br />
NameVirtualHost *:80<br /><br />
<VirtualHost 192.0.2.1:80><br />
ServerName namebased-a.example.com<br />
</VirtualHost><br />
<br />
<VirtualHost 192.0.2.1:80><br />
Servername namebased-b.example.com<br />
</VirtualHost><br />
<br />
<VirtualHost *:80><br />
ServerName namebased-c.example.com <br />
</VirtualHost><br />
<br />
<VirtualHost *:80><br />
ServerName namebased-d.example.com <br />
</VirtualHost><br />
<br />
</code></p></div>
<p>IPv6 addresses must be enclosed in square brackets, as shown
in the following example:</p>
<div class="example"><p><code>
NameVirtualHost [2001:db8::a00:20ff:fea7:ccea]:8080
</code></p></div>
<div class="note"><h3>Argument to <code class="directive"><VirtualHost></code>
directive</h3>
<p>Note that the argument to the <code class="directive"><VirtualHost></code> directive must
exactly match the argument to the <code class="directive">NameVirtualHost</code> directive.</p>
<div class="example"><p><code>
NameVirtualHost 192.0.2.2:80<br />
<VirtualHost 192.0.2.2:80><br />
# ...<br />
</VirtualHost><br />
</code></p></div>
</div>
<h3>See also</h3>
<ul>
documentation</a></li>
</ul>
</div>
<div class="directive-section"><h2><a name="Options" id="Options">Options</a> <a name="options" id="options">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures what features are available in a particular
directory</td></tr>
[+|-]<var>option</var> [[+|-]<var>option</var>] ...</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Options All</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">Options</code> directive controls which
server features are available in a particular directory.</p>
<p><var>option</var> can be set to <code>None</code>, in which
case none of the extra features are enabled, or one or more of
the following:</p>
<dl>
<dt><code>All</code></dt>
<dd>All options except for <code>MultiViews</code>. This is the default
setting.</dd>
<dt><code>ExecCGI</code></dt>
<dd>
is permitted.</dd>
<dt><code>FollowSymLinks</code></dt>
<dd>
The server will follow symbolic links in this directory.
<div class="note">
<p>Even though the server follows the symlink it does <em>not</em>
change the pathname used to match against <code class="directive"><a href="#directory"><Directory></a></code> sections.</p>
<p>Note also, that this option <strong>gets ignored</strong> if set
inside a <code class="directive"><a href="#location"><Location></a></code>
section.</p>
<p>Omitting this option should not be considered a security restriction,
since symlink testing is subject to race conditions that make it
circumventable.</p>
</div></dd>
<dt><code>Includes</code></dt>
<dd>
Server-side includes provided by <code class="module"><a href="/mod/mod_include.html">mod_include</a></code>
are permitted.</dd>
<dt><code>IncludesNOEXEC</code></dt>
<dd>
Server-side includes are permitted, but the <code>#exec
cmd</code> and <code>#exec cgi</code> are disabled. It is still
possible to <code>#include virtual</code> CGI scripts from
directories.</dd>
<dt><code>Indexes</code></dt>
<dd>
If a URL which maps to a directory is requested, and there
<code class="module"><a href="/mod/mod_autoindex.html">mod_autoindex</a></code> will return a formatted listing
of the directory.</dd>
<dt><code>MultiViews</code></dt>
<dd>
"MultiViews" are allowed using
<dt><code>SymLinksIfOwnerMatch</code></dt>
<dd>The server will only follow symbolic links for which the
target file or directory is owned by the same user id as the
link.
<div class="note"><h3>Note</h3> <p>This option gets ignored if
set inside a <code class="directive"><a href="#location"><Location></a></code> section.</p>
<p>This option should not be considered a security restriction,
since symlink testing is subject to race conditions that make it
circumventable.</p></div>
</dd>
</dl>
<p>Normally, if multiple <code class="directive">Options</code> could
apply to a directory, then the most specific one is used and
others are ignored; the options are not merged. (See <a href="/sections.html#mergin">how sections are merged</a>.)
However if <em>all</em> the options on the
<code class="directive">Options</code> directive are preceded by a
<code>+</code> or <code>-</code> symbol, the options are
merged. Any options preceded by a <code>+</code> are added to the
options currently in force, and any options preceded by a
<code>-</code> are removed from the options currently in
force. </p>
<div class="warning"><h3>Warning</h3>
<p>Mixing <code class="directive">Options</code> with a <code>+</code> or
<code>-</code> with those without is not valid syntax, and is likely
to cause unexpected results.</p>
</div>
<p>For example, without any <code>+</code> and <code>-</code> symbols:</p>
<div class="example"><p><code>
<span class="indent">
Options Indexes FollowSymLinks<br />
</span>
</Directory><br />
<br />
<span class="indent">
Options Includes<br />
</span>
</Directory>
</code></p></div>
<p>then only <code>Includes</code> will be set for the
<code class="directive">Options</code> directive uses the <code>+</code> and
<code>-</code> symbols:</p>
<div class="example"><p><code>
<span class="indent">
Options Indexes FollowSymLinks<br />
</span>
</Directory><br />
<br />
<span class="indent">
Options +Includes -Indexes<br />
</span>
</Directory>
</code></p></div>
<p>then the options <code>FollowSymLinks</code> and
directory.</p>
<div class="note"><h3>Note</h3>
<p>Using <code>-IncludesNOEXEC</code> or
<code>-Includes</code> disables server-side includes completely
regardless of the previous setting.</p>
</div>
<p>The default in the absence of any other settings is
<code>All</code>.</p>
</div>
<div class="directive-section"><h2><a name="RLimitCPU" id="RLimitCPU">RLimitCPU</a> <a name="rlimitcpu" id="rlimitcpu">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the CPU consumption of processes launched
by Apache children</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitCPU <var>seconds</var>|max [<var>seconds</var>|max]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or <code>max</code> to indicate to the server that the limit should
be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as <code>root</code>, or in the initial startup
phase.</p>
<p>This applies to processes forked off from Apache children
servicing requests, not the Apache children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache parent such as piped
logs.</p>
<p>CPU resource limits are expressed in seconds per
process.</p>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#rlimitmem">RLimitMEM</a></code></li>
<li><code class="directive"><a href="#rlimitnproc">RLimitNPROC</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="RLimitMEM" id="RLimitMEM">RLimitMEM</a> <a name="rlimitmem" id="rlimitmem">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the memory consumption of processes launched
by Apache children</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitMEM <var>bytes</var>|max [<var>bytes</var>|max]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or <code>max</code> to indicate to the server that the limit should
be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as <code>root</code>, or in the initial startup
phase.</p>
<p>This applies to processes forked off from Apache children
servicing requests, not the Apache children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache parent such as piped
logs.</p>
<p>Memory resource limits are expressed in bytes per
process.</p>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#rlimitcpu">RLimitCPU</a></code></li>
<li><code class="directive"><a href="#rlimitnproc">RLimitNPROC</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="RLimitNPROC" id="RLimitNPROC">RLimitNPROC</a> <a name="rlimitnproc" id="rlimitnproc">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the number of processes that can be launched by
processes launched by Apache children</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitNPROC <var>number</var>|max [<var>number</var>|max]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or <code>max</code> to indicate to the server that the limit
should be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as <code>root</code>, or in the initial startup
phase.</p>
<p>This applies to processes forked off from Apache children
servicing requests, not the Apache children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache parent such as piped
logs.</p>
<p>Process limits control the number of processes per user.</p>
<div class="note"><h3>Note</h3>
<p>If CGI processes are <strong>not</strong> running
under user ids other than the web server user id, this directive
will limit the number of processes that the server itself can
create. Evidence of this situation will be indicated by
<strong><code>cannot fork</code></strong> messages in the
<code>error_log</code>.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#rlimitmem">RLimitMEM</a></code></li>
<li><code class="directive"><a href="#rlimitcpu">RLimitCPU</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="ScriptInterpreterSource" id="ScriptInterpreterSource">ScriptInterpreterSource</a> <a name="scriptinterpretersource" id="scriptinterpretersource">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Technique for locating the interpreter for CGI
scripts</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScriptInterpreterSource Registry|Registry-Strict|Script</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScriptInterpreterSource Script</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
option <code>Registry-Strict</code> is available in Apache 2.0 and
later</td></tr>
</table>
<p>This directive is used to control how Apache finds the
interpreter used to run CGI scripts. The default setting is
<code>Script</code>. This causes Apache to use the interpreter pointed to
by the shebang line (first line, starting with <code>#!</code>) in the
script. On Win32 systems this line usually looks like:</p>
<div class="example"><p><code>
</code></p></div>
<p>or, if <code>perl</code> is in the <code>PATH</code>, simply:</p>
<div class="example"><p><code>
#!perl
</code></p></div>
<p>Setting <code>ScriptInterpreterSource Registry</code> will
cause the Windows Registry tree <code>HKEY_CLASSES_ROOT</code> to be
search key. The command defined by the registry subkey
<code>Shell\ExecCGI\Command</code> or, if it does not exist, by the subkey
<code>Shell\Open\Command</code> is used to open the script file. If the
registry keys cannot be found, Apache falls back to the behavior of the
<code>Script</code> option.</p>
<div class="warning"><h3>Security</h3>
<p>Be careful when using <code>ScriptInterpreterSource
Registry</code> with <code class="directive"><a href="/mod/mod_alias.html#scriptalias">ScriptAlias</a></code>'ed directories, because
Apache will try to execute <strong>every</strong> file within this
directory. The <code>Registry</code> setting may cause undesired
program calls on files which are typically not executed. For
example, the default open command on <code>.htm</code> files on
most Windows systems will execute Microsoft Internet Explorer, so
any HTTP request for an <code>.htm</code> file existing within the
script directory would start the browser in the background on the
server. This is a good way to crash your system within a minute or
so.</p>
</div>
<p>The option <code>Registry-Strict</code> which is new in Apache
2.0 does the same thing as <code>Registry</code> but uses only the
subkey <code>Shell\ExecCGI\Command</code>. The
<code>ExecCGI</code> key is not a common one. It must be
configured manually in the windows registry and hence prevents
accidental program calls on your system.</p>
</div>
<div class="directive-section"><h2><a name="ServerAdmin" id="ServerAdmin">ServerAdmin</a> <a name="serveradmin" id="serveradmin">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Email address that the server includes in error
messages sent to the client</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerAdmin <var>email-address</var>|<var>URL</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive">ServerAdmin</code> sets the contact address
that the server includes in any error messages it returns to the
client. If the <code>httpd</code> doesn't recognize the supplied argument
as an URL, it
assumes, that it's an <var>email-address</var> and prepends it with
<code>mailto:</code> in hyperlink targets. However, it's recommended to
actually use an email address, since there are a lot of CGI scripts that
make that assumption. If you want to use an URL, it should point to another
server under your control. Otherwise users may not be able to contact you in
case of errors.</p>
<div class="example"><p><code>
ServerAdmin www-admin@foo.example.com
</code></p></div>
<p>as users do not always mention that they are talking about the
server!</p>
</div>
<div class="directive-section"><h2><a name="ServerAlias" id="ServerAlias">ServerAlias</a> <a name="serveralias" id="serveralias">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Alternate names for a host used when matching requests
to name-virtual hosts</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerAlias <var>hostname</var> [<var>hostname</var>] ...</code></td></tr>
</table>
<p>The <code class="directive">ServerAlias</code> directive sets the
alternate names for a host, for use with <a href="/vhosts/name-based.html">name-based virtual hosts</a>. The
<code class="directive">ServerAlias</code> may include wildcards, if appropriate.</p>
<div class="example"><p><code>
<VirtualHost *:80><br />
ServerName server.domain.com<br />
ServerAlias server server2.domain.com server2<br />
ServerAlias *.example.com<br />
# ...<br />
</VirtualHost>
</code></p></div>
<h3>See also</h3>
<ul>
</ul>
</div>
<div class="directive-section"><h2><a name="ServerName" id="ServerName">ServerName</a> <a name="servername" id="servername">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Hostname and port that the server uses to identify
itself</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerName [<var>scheme</var>://]<var>fully-qualified-domain-name</var>[:<var>port</var>]</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
directive supersedes the functionality of the <code class="directive">Port</code>
directive from version 1.3.</td></tr>
</table>
<p>The <code class="directive">ServerName</code> directive sets the
request scheme, hostname and
port that the server uses to identify itself. This is used when
creating redirection URLs. For example, if the name of the
and you wish the web server to be so identified, the following
directive should be used:</p>
<div class="example"><p><code>
ServerName www.example.com:80
</code></p></div>
<p>If no <code class="directive">ServerName</code> is specified, then the
server attempts to deduce the hostname by performing a reverse
lookup on the IP address. If no port is specified in the
<code class="directive">ServerName</code>, then the server will use the
port from the incoming request. For optimal reliability and
predictability, you should specify an explicit hostname and port
using the <code class="directive">ServerName</code> directive.</p>
the <code class="directive">ServerName</code> inside a
<code class="directive"><a href="#virtualhost"><VirtualHost></a></code>
section specifies what hostname must appear in the request's
<code>Host:</code> header to match this virtual host.</p>
<p>Sometimes, the server runs behind a device that processes SSL,
such as a reverse proxy, load balancer or SSL offload
appliance. When this is the case, specify the
<code>https://</code> scheme and the port number to which the
clients connect in the <code class="directive">ServerName</code> directive
to make sure that the server generates the correct
self-referential URLs.
</p>
<p>See the description of the
<code class="directive"><a href="#usecanonicalname">UseCanonicalName</a></code> and
<code class="directive"><a href="#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></code> directives for
settings which determine whether self-referential URLs (e.g., by the
specified port, or to the port number given in the client's request.
</p>
<h3>See also</h3>
<ul>
Apache</a></li>
documentation</a></li>
<li><code class="directive"><a href="#usecanonicalname">UseCanonicalName</a></code></li>
<li><code class="directive"><a href="#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></code></li>
<li><code class="directive"><a href="#namevirtualhost">NameVirtualHost</a></code></li>
<li><code class="directive"><a href="#serveralias">ServerAlias</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="ServerPath" id="ServerPath">ServerPath</a> <a name="serverpath" id="serverpath">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Legacy URL pathname for a name-based virtual host that
is accessed by an incompatible browser</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerPath <var>URL-path</var></code></td></tr>
</table>
<p>The <code class="directive">ServerPath</code> directive sets the legacy
<h3>See also</h3>
<ul>
</ul>
</div>
<div class="directive-section"><h2><a name="ServerRoot" id="ServerRoot">ServerRoot</a> <a name="serverroot" id="serverroot">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Base directory for the server installation</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerRoot <var>directory-path</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ServerRoot /usr/local/apache</code></td></tr>
</table>
<p>The <code class="directive">ServerRoot</code> directive sets the
directory in which the server lives. Typically it will contain the
subdirectories <code>conf/</code> and <code>logs/</code>. Relative
paths in other configuration directives (such as <code class="directive"><a href="#include">Include</a></code> or <code class="directive"><a href="/mod/mod_so.html#loadmodule">LoadModule</a></code>, for example) are taken as
relative to this directory.</p>
<div class="example"><h3>Example</h3><p><code>
</code></p></div>
<h3>See also</h3>
<ul>
option to <code>httpd</code></a></li>
security tips</a> for information on how to properly set
permissions on the <code class="directive">ServerRoot</code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="ServerSignature" id="ServerSignature">ServerSignature</a> <a name="serversignature" id="serversignature">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures the footer on server-generated documents</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerSignature On|Off|EMail</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ServerSignature Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">ServerSignature</code> directive allows the
configuration of a trailing footer line under server-generated
documents (error messages, <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code> ftp directory
listings, <code class="module"><a href="/mod/mod_info.html">mod_info</a></code> output, ...). The reason why you
would want to enable such a footer line is that in a chain of proxies,
the user often has no possibility to tell which of the chained servers
actually produced a returned error message.</p>
<p>The <code>Off</code>
setting, which is the default, suppresses the footer line (and is
therefore compatible with the behavior of Apache-1.2 and
below). The <code>On</code> setting simply adds a line with the
server version number and <code class="directive"><a href="#servername">ServerName</a></code> of the serving virtual host,
and the <code>EMail</code> setting additionally creates a
"mailto:" reference to the <code class="directive"><a href="#serveradmin">ServerAdmin</a></code> of the referenced
document.</p>
<p>After version 2.0.44, the details of the server version number
presented are controlled by the <code class="directive"><a href="#servertokens">ServerTokens</a></code> directive.</p>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#servertokens">ServerTokens</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="ServerTokens" id="ServerTokens">ServerTokens</a> <a name="servertokens" id="servertokens">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures the <code>Server</code> HTTP response
header</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerTokens Major|Minor|Min[imal]|Prod[uctOnly]|OS|Full|Off|Set</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ServerTokens Full</code></td></tr>
</table>
<p>This directive controls whether <code>Server</code> response
header field which is sent back to clients includes a
description of the generic OS-type of the server as well as
information about compiled-in modules.</p>
<dl>
<dt><code>ServerTokens Full</code> (or not specified)</dt>
<dt><code>ServerTokens Prod[uctOnly]</code></dt>
Apache</code></dd>
<dt><code>ServerTokens Major</code></dt>
Apache/2</code></dd>
<dt><code>ServerTokens Minor</code></dt>
<dt><code>ServerTokens Min[imal]</code></dt>
<dt><code>ServerTokens OS</code></dt>
(Unix)</code></dd>
<dt><code>ServerTokens Set <em>"String"</em></code></dt>
<dd>Server sends user specified string
<strong>Note:</strong> The string must be in quotes if
there are any embedded spaces.
</dd>
<dt><code>ServerTokens Off</code></dt>
<dd>Server sends no <code>Server:</code> header
(and <code>SERVER_SOFTWARE</code> is blank)</dd>
</dl>
<p>This setting applies to the entire server, and cannot be
enabled or disabled on a virtualhost-by-virtualhost basis.</p>
<p>After version 2.0.44, this directive also controls the
information presented by the <code class="directive"><a href="#serversignature">ServerSignature</a></code> directive.</p>
<div class="note">Setting <code class="directive">ServerTokens</code> to less than
<code>minimal</code> is not recommended because it makes it more
difficult to debug interoperational problems. Also note that
disabling the Server: header does nothing at all to make your
server more secure; the idea of "security through obscurity"
is a myth and leads to a false sense of safety.</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#serversignature">ServerSignature</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="SetHandler" id="SetHandler">SetHandler</a> <a name="sethandler" id="sethandler">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Forces all matching files to be processed by a
handler</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SetHandler <var>handler-name</var>|None</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Moved into the core in Apache 2.0</td></tr>
</table>
<p>When placed into an <code>.htaccess</code> file or a
<code class="directive"><a href="#directory"><Directory></a></code> or
<code class="directive"><a href="#location"><Location></a></code>
section, this directive forces all matching files to be parsed
<var>handler-name</var>. For example, if you had a directory you
wanted to be parsed entirely as imagemap rule files, regardless
of extension, you might put the following into an
<code>.htaccess</code> file in that directory:</p>
<div class="example"><p><code>
SetHandler imap-file
</code></p></div>
<p>Another example: if you wanted to have the server display a
status report whenever a URL of
<div class="example"><p><code>
<Location /status><br />
<span class="indent">
SetHandler server-status<br />
</span>
</Location>
</code></p></div>
<p>You can override an earlier defined <code class="directive">SetHandler</code>
directive by using the value <code>None</code>.</p>
<p><strong>Note:</strong> because SetHandler overrides default handlers,
normal behaviour such as handling of URLs ending in a slash (/) as
directories or index files is suppressed.</p>
<h3>See also</h3>
<ul>
</ul>
</div>
<div class="directive-section"><h2><a name="SetInputFilter" id="SetInputFilter">SetInputFilter</a> <a name="setinputfilter" id="setinputfilter">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the filters that will process client requests and POST
input</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SetInputFilter <var>filter</var>[;<var>filter</var>...]</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">SetInputFilter</code> directive sets the
filter or filters which will process client requests and POST
input when they are received by the server. This is in addition to
any filters defined elsewhere, including the
directive.</p>
<p>If more than one filter is specified, they must be separated
by semicolons in the order in which they should process the
content.</p>
<h3>See also</h3>
<ul>
</ul>
</div>
<div class="directive-section"><h2><a name="SetOutputFilter" id="SetOutputFilter">SetOutputFilter</a> <a name="setoutputfilter" id="setoutputfilter">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the filters that will process responses from the
server</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SetOutputFilter <var>filter</var>[;<var>filter</var>...]</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">SetOutputFilter</code> directive sets the filters
which will process responses from the server before they are
sent to the client. This is in addition to any filters defined
elsewhere, including the
directive.</p>
<p>For example, the following configuration will process all files
includes.</p>
<div class="example"><p><code>
<span class="indent">
SetOutputFilter INCLUDES<br />
</span>
</Directory>
</code></p></div>
<p>If more than one filter is specified, they must be separated
by semicolons in the order in which they should process the
content.</p>
<h3>See also</h3>
<ul>
</ul>
</div>
<div class="directive-section"><h2><a name="TimeOut" id="TimeOut">TimeOut</a> <a name="timeout" id="timeout">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Amount of time the server will wait for
certain events before failing a request</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>TimeOut <var>seconds</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>TimeOut 300</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive">TimeOut</code> directive defines the length
of time Apache will wait for I/O in various circumstances:</p>
<ol>
<li>When reading data from the client, the length of time to
wait for a TCP packet to arrive if the read buffer is
empty.</li>
<li>When writing data to the client, the length of time to wait
for an acknowledgement of a packet if the send buffer is
full.</li>
<li>In <code class="module"><a href="/mod/mod_cgi.html">mod_cgi</a></code>, the length of time to wait for
output from a CGI script.</li>
<li>In <code class="module"><a href="/mod/mod_ext_filter.html">mod_ext_filter</a></code>, the length of time to
wait for output from a filtering process.</li>
<li>In <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code>, the default timeout value if
configured.</li>
</ol>
</div>
<div class="directive-section"><h2><a name="TraceEnable" id="TraceEnable">TraceEnable</a> <a name="traceenable" id="traceenable">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determines the behaviour on <code>TRACE</code>
requests</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>TraceEnable <var>[on|off|extended]</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>TraceEnable on</code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 1.3.34, 2.0.55 and later</td></tr>
</table>
<p>This directive overrides the behavior of <code>TRACE</code> for both
the core server and <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code>. The default
<code>TraceEnable on</code> permits <code>TRACE</code> requests per
RFC 2616, which disallows any request body to accompany the request.
<code>TraceEnable off</code> causes the core server and
<code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code> to return a <code>405</code> (Method not
allowed) error to the client.</p>
<p>Finally, for testing and diagnostic purposes only, request
bodies may be allowed using the non-compliant <code>TraceEnable
extended</code> directive. The core (as an origin server) will
restrict the request body to 64k (plus 8k for chunk headers if
<code>Transfer-Encoding: chunked</code> is used). The core will
reflect the full headers and all chunk headers with the response
body. As a proxy server, the request body is not restricted to 64k.</p>
</div>
<div class="directive-section"><h2><a name="UseCanonicalName" id="UseCanonicalName">UseCanonicalName</a> <a name="usecanonicalname" id="usecanonicalname">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures how the server determines its own name and
port</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>UseCanonicalName On|Off|DNS</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>UseCanonicalName Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
</table>
<p>In many situations Apache must construct a <em>self-referential</em>
URL -- that is, a URL that refers back to the same server. With
<code>UseCanonicalName On</code> Apache will use the hostname and port
specified in the <code class="directive"><a href="#servername">ServerName</a></code>
directive to construct the canonical name for the server. This name
is used in all self-referential URLs, and for the values of
<code>SERVER_NAME</code> and <code>SERVER_PORT</code> in CGIs.</p>
<p>With <code>UseCanonicalName Off</code> Apache will form
self-referential URLs using the hostname and port supplied by
the client if any are supplied (otherwise it will use the
canonical name, as defined above). These values are the same
and are available with the same clients. The CGI variables
<code>SERVER_NAME</code> and <code>SERVER_PORT</code> will be
constructed from the client supplied values as well.</p>
<p>An example where this may be useful is on an intranet server
where you have users connecting to the machine using short
names such as <code>www</code>. You'll notice that if the users
type a shortname, and a URL which is a directory, such as
slash</em> then Apache will redirect them to
authentication enabled, this will cause the user to have to
authenticate twice (once for <code>www</code> and once again
for <code>www.domain.com</code> -- see <a href="http://httpd.apache.org/docs/misc/FAQ.html#prompted-twice">the
FAQ on this subject for more information</a>). But if
<code class="directive">UseCanonicalName</code> is set <code>Off</code>, then
<p>There is a third option, <code>UseCanonicalName DNS</code>,
which is intended for use with mass IP-based virtual hosting to
support ancient clients that do not provide a
<code>Host:</code> header. With this option Apache does a
reverse DNS lookup on the server IP address that the client
connected to in order to work out self-referential URLs.</p>
<div class="warning"><h3>Warning</h3>
<p>If CGIs make assumptions about the values of <code>SERVER_NAME</code>
they may be broken by this option. The client is essentially free
to give whatever value they want as a hostname. But if the CGI is
only using <code>SERVER_NAME</code> to construct self-referential URLs
then it should be just fine.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></code></li>
<li><code class="directive"><a href="#servername">ServerName</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="UseCanonicalPhysicalPort" id="UseCanonicalPhysicalPort">UseCanonicalPhysicalPort</a> <a name="usecanonicalphysicalport" id="usecanonicalphysicalport">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures how the server determines its own name and
port</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>UseCanonicalPhysicalPort On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>UseCanonicalPhysicalPort Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
</table>
<p>In many situations Apache must construct a <em>self-referential</em>
URL -- that is, a URL that refers back to the same server. With
<code>UseCanonicalPhysicalPort On</code> Apache will, when
constructing the canonical port for the server to honor
the <code class="directive"><a href="#usecanonicalname">UseCanonicalName</a></code> directive,
provide the actual physical port number being used by this request
as a potential port. With <code>UseCanonicalPhysicalPort Off</code>
Apache will not ever use the actual physical port number, instead
relying on all configured information to construct a valid port number.</p>
<div class="note"><h3>Note</h3>
<p>The ordering of when the physical port is used is as follows:<br /><br />
<code>UseCanonicalName On</code></p>
<ul>
<li>Port provided in <code>Servername</code></li>
<li>Physical port</li>
<li>Default port</li>
</ul>
<code>UseCanonicalName Off | DNS</code>
<ul>
<li>Parsed port from <code>Host:</code> header</li>
<li>Physical port</li>
<li>Port provided in <code>Servername</code></li>
<li>Default port</li>
</ul>
<p>With <code>UseCanonicalPhysicalPort Off</code>, the
physical ports are removed from the ordering.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#usecanonicalname">UseCanonicalName</a></code></li>
<li><code class="directive"><a href="#servername">ServerName</a></code></li>
</ul>
</div>
<div class="directive-section"><h2><a name="VirtualHost" id="VirtualHost"><VirtualHost></a> <a name="virtualhost" id="virtualhost">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Contains directives that apply only to a specific
hostname or IP address</td></tr>
<var>addr</var>[:<var>port</var>] [<var>addr</var>[:<var>port</var>]]
...> ... </VirtualHost></code></td></tr>
</table>
<p><code class="directive"><VirtualHost></code> and
<code></VirtualHost></code> are used to enclose a group of
directives that will apply only to a particular virtual host. Any
directive that is allowed in a virtual host context may be
used. When the server receives a request for a document on a
particular virtual host, it uses the configuration directives
enclosed in the <code class="directive"><VirtualHost></code>
section. <var>Addr</var> can be:</p>
<ul>
<li>The IP address of the virtual host;</li>
<li>A fully qualified domain name for the IP address of the
virtual host (not recommended);</li>
<li>The character <code>*</code>, which is used only in combination with
<code>NameVirtualHost *</code> to match all IP addresses; or</li>
<li>The string <code>_default_</code>, which is used only
with IP virtual hosting to catch unmatched IP addresses.</li>
</ul>
<div class="example"><h3>Example</h3><p><code>
<VirtualHost 10.1.2.3><br />
<span class="indent">
ServerAdmin webmaster@host.example.com<br />
ServerName host.example.com<br />
</span>
</VirtualHost>
</code></p></div>
<p>IPv6 addresses must be specified in square brackets because
the optional port number could not be determined otherwise. An
IPv6 example is shown below:</p>
<div class="example"><p><code>
<VirtualHost [2001:db8::a00:20ff:fea7:ccea]><br />
<span class="indent">
ServerAdmin webmaster@host.example.com<br />
ServerName host.example.com<br />
</span>
</VirtualHost>
</code></p></div>
<p>Each Virtual Host must correspond to a different IP address,
different port number or a different host name for the server,
in the former case the server machine must be configured to
accept IP packets for multiple addresses. (If the machine does
not have multiple network interfaces, then this can be
accomplished with the <code>ifconfig alias</code> command -- if
your OS supports it).</p>
<div class="note"><h3>Note</h3>
<p>The use of <code class="directive"><VirtualHost></code> does
<strong>not</strong> affect what addresses Apache listens on. You
may need to ensure that Apache is listening on the correct addresses
</div>
<p>When using IP-based virtual hosting, the special name
<code>_default_</code> can be specified in
which case this virtual host will match any IP address that is
not explicitly listed in another virtual host. In the absence
of any <code>_default_</code> virtual host the "main" server config,
consisting of all those definitions outside any VirtualHost
section, is used when no IP-match occurs.</p>
<p>You can specify a <code>:port</code> to change the port that is
matched. If unspecified then it defaults to the same port as the
statement of the main server. You may also specify <code>:*</code>
to match all ports on that address. (This is recommended when used
with <code>_default_</code>.)</p>
<p>A <code class="directive"><a href="#servername">ServerName</a></code> should be
specified inside each <code class="directive"><VirtualHost></code> block. If it is absent, the
<code class="directive"><a href="#servername">ServerName</a></code> from the "main"
server configuration will be inherited.</p>
<div class="warning"><h3>Security</h3>
document for details on why your security could be compromised if the
directory where log files are stored is writable by anyone other
than the user that starts the server.</p>
</div>
<h3>See also</h3>
<ul>
Apache</a></li>
which addresses and ports Apache uses</a></li>
and <Files> sections work</a> for an explanation of how these
different sections are combined when a request is received</li>
</ul>
</div>
</div>
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