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<?xml version="1.0"?>
<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.es.xsl"?>
<!-- English Revision: 1741251:1841039 (outdated) -->
<!-- Translated by Luis Gil de Bernabé Pfeiffer lgilbernabe[AT]apache.org -->
<!-- Reviewed by Sergio Ramos-->
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<modulesynopsis metafile="core.xml.meta">
<name>core</name>
<description>Funcionalides b&#225;sicas del Servidor HTTP Apache que siempre est&#225;n presentes.</description>
<status>Core</status>
<directivesynopsis>
<name>AcceptFilter</name>
<description>Configura mejoras para un Protocolo de Escucha de Sockets</description>
<syntax>AcceptFilter <var>protocol</var> <var>accept_filter</var></syntax>
<contextlist><context>server config</context></contextlist>
<compatibility>Disponible en Apache httpd 2.1.5 y posteriores.
En Windows desde Apache httpd 2.3.3 y posteriores.</compatibility>
<usage>
<p>Esta directiva hace posible mejoras espec&#237;ficas a nivel de sistema operativo
y a trav&#233;s del tipo de Protocolo para un socket que escucha.
La premisa b&#225;sica es que el kernel no env&#237;e un socket al servidor
hasta que o bien los datos se hayan recibido o bien se haya almacenado
en el buffer una Respuesta HTTP completa.
Actualmente s&#243;lo est&#225;n soportados
<a href="http://www.freebsd.org/cgi/man.cgi?query=accept_filter&amp;sektion=9">
Accept Filters</a> sobre FreeBSD, <code>TCP_DEFER_ACCEPT</code> sobre Linux,
y AcceptEx() sobre Windows.</p>
<p>El uso de <code>none</code> para un argumento desactiva cualquier filtro
aceptado para ese protocolo. Esto es &#250;til para protocolos que requieren que un
servidor env&#237;e datos primeros, tales como <code>ftp:</code> o <code>nntp</code>:</p>
<example>AcceptFilter nntp none</example>
<p>Los nombres de protocolo por defecto son <code>https</code> para el puerto 443
y <code>http</code> para todos los dem&#225;s puertos. Para especificar que se est&#225;
utilizando otro protocolo con un puerto escuchando, a&#241;ade el argumento <var>protocol</var>
a la directiva <directive module="mpm_common">Listen</directive>.</p>
<p>Sobre FreeBDS los valores por defecto:</p>
<example>
AcceptFilter http httpready <br/>
AcceptFilter https dataready
</example>
<p>El filtro <code>httpready</code> almacena en el buffer peticiones HTTP completas
a nivel de kernel. Una vez que la petici&#243;n es recibida, el kernel la env&#237;a al servidor.
Consulta la p&#225;gina man de
<a href="http://www.freebsd.org/cgi/man.cgi?query=accf_http&amp;sektion=9">
accf_http(9)</a> para m&#225;s detalles. Puesto que las peticiones HTTPS
est&#225;n encriptadas, s&#243;lo se utiliza el filtro
<a href="http://www.freebsd.org/cgi/man.cgi?query=accf_data&amp;sektion=9">accf_data(9)</a>.</p>
<p>Sobre Linux los valores por defecto son:</p>
<example>
AcceptFilter http data <br/>
AcceptFilter https data
</example>
<p>En Linux, <code>TCP_DEFER_ACCEPT</code> no soporta el buffering en peticiones http.
Cualquier valor adem&#225;s de <code>none</code> habilitar&#225;
<code>TCP_DEFER_ACCEPT</code> en ese socket. Para m&#225;s detalles
ver la p&#225;gina man de Linux
<a href="http://homepages.cwi.nl/~aeb/linux/man2html/man7/tcp.7.html">
tcp(7)</a>.</p>
<p>Sobre Windows los valores por defecto son:</p>
<example>
AcceptFilter http data <br/>
AcceptFilter https data
</example>
<p>Sobre Windows mpm_winnt interpreta el argumento AcceptFilter para conmutar la API
AcceptEx(), y no soporta el buffering sobre el protocolo http. Hay dos valores
que utilizan la API Windows AcceptEx() y que recuperan sockets de red
entre conexciones. <code>data</code> espera hasta que los datos han sido
transmitidos como se comentaba anteriormente, y el buffer inicial de datos y las
direcciones de red son recuperadas a partir de una &#250;nica llamada AcceptEx().
<code>connect</code> utiliza la API AcceptEx() API, y recupera tambi&#233;n
las direcciones de red, pero a diferencia de <code>none</code>
la opci&#243;n <code>connect</code> no espera a la transmisi&#243;n inicial de los datos.</p>
<p>Sobre Windows, <code>none</code> prefiere accept() antes que AcceptEx()
y no recuperar&#225; sockets entre las conexiones. Lo que es &#250;til para los adaptadores de
red con un soporte precario de drivers, as&#237; como para algunos proveedores de red
tales como drivers vpn, o filtros de spam, de virus o de spyware.</p>
</usage>
<seealso><directive>Protocol</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AcceptPathInfo</name>
<description>Los recursos aceptan informaci&#243;n sobre su ruta</description>
<syntax>AcceptPathInfo On|Off|Default</syntax>
<default>AcceptPathInfo Default</default>
<contextlist><context>server config</context>
<context>virtual host</context><context>directory</context>
<context>.htaccess</context></contextlist>
<override>FileInfo</override>
<compatibility>Disponible en Apache httpd 2.0.30 y posteriores</compatibility>
<usage>
<p>Esta directiva controla si las peticiones que contienen informaci&#243;n sobre la ruta
que sigue un fichero que existe (o un fichero que no existe pero en un directorio que
s&#237; existe) ser&#225;n aceptadas o denegadas. La informaci&#243;n de ruta puede estar disponible
para los scripts en la variable de entorno <code>PATH_INFO</code>.</p>
<p>Por ejemplo, asumamos que la ubicaci&#243;n <code>/test/</code> apunta a
un directorio que contiene &#250;nicamente el fichero
<code>here.html</code>. Entonces, las peticiones tanto para
<code>/test/here.html/more</code> como para
<code>/test/nothere.html/more</code> recogen
<code>/more</code> como <code>PATH_INFO</code>.</p>
<p>Los tres posibles argumentos para la directiva
<directive>AcceptPathInfo</directive> son los siguientes:</p>
<dl>
<dt><code>Off</code></dt><dd>Una petici&#243;n s&#243;lo ser&#225; aceptada si
se corresponde con una ruta literal que existe. Por lo tanto, una petici&#243;n
con una informaci&#243;n de ruta despu&#233;s del nombre de fichero tal como
<code>/test/here.html/more</code> en el ejemplo anterior devolver&#225;
un error 404 NOT FOUND.</dd>
<dt><code>On</code></dt><dd>Una petici&#243;n ser&#225; aceptada si una
ruta principal de acceso se corresponde con un fichero que existe. El ejemplo
anterior <code>/test/here.html/more</code> ser&#225; aceptado si
<code>/test/here.html</code> corresponde a un fichero v&#225;lido.</dd>
<dt><code>Default</code></dt><dd>La gesti&#243;n de las peticiones
con informaci&#243;n de ruta est&#225; determinada por el <a
href="../handler.html">controlador</a> responsable de la petici&#243;n.
El controlador principal para para ficheros normales rechaza por defecto
peticiones <code>PATH_INFO</code>. Los controladores que sirven scripts, tales como <a
href="mod_cgi.html">cgi-script</a> e <a
href="mod_isapi.html">isapi-handler</a>, normalmente aceptan
<code>PATH_INFO</code> por defecto.</dd>
</dl>
<p>El objetivo principal de la directiva <code>AcceptPathInfo</code>
es permitirte sobreescribir la opci&#243;n del controlador
de aceptar or rechazar <code>PATH_INFO</code>. Este tipo de sobreescritura se necesita,
por ejemplo, cuando utilizas un <a href="../filter.html">filtro</a>, tal como
<a href="mod_include.html">INCLUDES</a>, para generar contenido
basado en <code>PATH_INFO</code>. El controlador principal normalmente rechazar&#237;a
la petici&#243;n, de modo que puedes utilizar la siguiente configuraci&#243;n para habilitarla
como script:</p>
<example>
&lt;Files "mypaths.shtml"&gt;<br />
<indent>
Options +Includes<br />
SetOutputFilter INCLUDES<br />
AcceptPathInfo On<br />
</indent>
&lt;/Files&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AccessFileName</name>
<description>Nombre del fichero distribuido de configuraci&#243;n</description>
<syntax>AccessFileName <var>filename</var> [<var>filename</var>] ...</syntax>
<default>AccessFileName .htaccess</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>Mientras que procesa una petici&#243;n el servidor busca
el primer fichero de configuraci&#243;n existente dentro de un listado de nombres en
cada directorio de la ruta del documento, si los ficheros distribuidos
de configuraci&#243;n est&#225;n <a href="#allowoverride">habilitados para ese
directorio</a>. Por ejemplo:</p>
<example>
AccessFileName .acl
</example>
<p>antes de servir el documento
<code>/usr/local/web/index.html</code>, el servidor leer&#225;
<code>/.acl</code>, <code>/usr/.acl</code>,
<code>/usr/local/.acl</code> and <code>/usr/local/web/.acl</code>
para las directivas, salvo que estén deshabilitadas with</p>
<example>
&lt;Directory /&gt;<br />
<indent>
AllowOverride None<br />
</indent>
&lt;/Directory&gt;
</example>
</usage>
<seealso><directive module="core">AllowOverride</directive></seealso>
<seealso><a href="../configuring.html">Configuration Files</a></seealso>
<seealso><a href="../howto/htaccess.html">.htaccess Files</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AddDefaultCharset</name>
<description>Default charset parameter to be added when a response
content-type is <code>text/plain</code> or <code>text/html</code></description>
<syntax>AddDefaultCharset On|Off|<var>charset</var></syntax>
<default>AddDefaultCharset Off</default>
<contextlist><context>server config</context>
<context>virtual host</context><context>directory</context>
<context>.htaccess</context></contextlist>
<override>FileInfo</override>
<usage>
<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
<code>text/plain</code> or <code>text/html</code>. This should override
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>
<example>
AddDefaultCharset utf-8
</example>
<p><directive>AddDefaultCharset</directive> 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>
</usage>
<seealso><directive module="mod_mime">AddCharset</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AllowEncodedSlashes</name>
<description>Determines whether encoded path separators in URLs are allowed to
be passed through</description>
<syntax>AllowEncodedSlashes On|Off</syntax>
<default>AllowEncodedSlashes Off</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Available in Apache httpd 2.0.46 and later</compatibility>
<usage>
<p>The <directive>AllowEncodedSlashes</directive> 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 <directive>AllowEncodedSlashes</directive> <code>On</code> is
mostly useful when used in conjunction with <code>PATH_INFO</code>.</p>
<note><title>Note</title>
<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>
</note>
</usage>
<seealso><directive module="core">AcceptPathInfo</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AllowOverride</name>
<description>Types of directives that are allowed in
<code>.htaccess</code> files</description>
<syntax>AllowOverride All|None|<var>directive-type</var>
[<var>directive-type</var>] ...</syntax>
<default>AllowOverride None (2.3.9 and later), AllowOverride All (2.3.8 and earlier)</default>
<contextlist><context>directory</context></contextlist>
<usage>
<p>When the server finds an <code>.htaccess</code> file (as
specified by <directive module="core">AccessFileName</directive>)
it needs to know which directives declared in that file can override
earlier configuration directives.</p>
<note><title>Only available in &lt;Directory&gt; sections</title>
<directive>AllowOverride</directive> is valid only in
<directive type="section" module="core">Directory</directive>
sections specified without regular expressions, not in <directive
type="section" module="core">Location</directive>, <directive
module="core" type="section">DirectoryMatch</directive> or
<directive type="section" module="core">Files</directive> sections.
</note>
<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
directive which has the .htaccess <a
href="directive-dict.html#Context">Context</a> is allowed in
<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 (<directive
module="mod_authn_dbm">AuthDBMGroupFile</directive>,
<directive module="mod_authn_dbm">AuthDBMUserFile</directive>,
<directive module="mod_authz_groupfile">AuthGroupFile</directive>,
<directive module="mod_authn_core">AuthName</directive>,
<directive module="mod_authn_core">AuthType</directive>, <directive
module="mod_authn_file">AuthUserFile</directive>, <directive
module="mod_authz_core">Require</directive>, <em>etc.</em>).</dd>
<dt>FileInfo</dt>
<dd>
Allow use of the directives controlling document types
(<directive module="core">ErrorDocument</directive>,
<directive module="core">ForceType</directive>,
<directive module="mod_negotiation">LanguagePriority</directive>,
<directive module="core">SetHandler</directive>,
<directive module="core">SetInputFilter</directive>,
<directive module="core">SetOutputFilter</directive>, and
<module>mod_mime</module> Add* and Remove* directives),
document meta data (<directive
module="mod_headers">Header</directive>, <directive
module="mod_headers">RequestHeader</directive>, <directive
module="mod_setenvif">SetEnvIf</directive>, <directive
module="mod_setenvif">SetEnvIfNoCase</directive>, <directive
module="mod_setenvif">BrowserMatch</directive>, <directive
module="mod_usertrack">CookieExpires</directive>, <directive
module="mod_usertrack">CookieDomain</directive>, <directive
module="mod_usertrack">CookieStyle</directive>, <directive
module="mod_usertrack">CookieTracking</directive>, <directive
module="mod_usertrack">CookieName</directive>),
<module>mod_rewrite</module> directives <directive
module="mod_rewrite">RewriteEngine</directive>, <directive
module="mod_rewrite">RewriteOptions</directive>, <directive
module="mod_rewrite">RewriteBase</directive>, <directive
module="mod_rewrite">RewriteCond</directive>, <directive
module="mod_rewrite">RewriteRule</directive>) and
<directive module="mod_actions">Action</directive> from
<module>mod_actions</module>.
</dd>
<dt>Indexes</dt>
<dd>
Allow use of the directives controlling directory indexing
(<directive
module="mod_autoindex">AddDescription</directive>,
<directive module="mod_autoindex">AddIcon</directive>, <directive
module="mod_autoindex">AddIconByEncoding</directive>,
<directive module="mod_autoindex">AddIconByType</directive>,
<directive module="mod_autoindex">DefaultIcon</directive>, <directive
module="mod_dir">DirectoryIndex</directive>, <directive
module="mod_autoindex">FancyIndexing</directive>, <directive
module="mod_autoindex">HeaderName</directive>, <directive
module="mod_autoindex">IndexIgnore</directive>, <directive
module="mod_autoindex">IndexOptions</directive>, <directive
module="mod_autoindex">ReadmeName</directive>,
<em>etc.</em>).</dd>
<dt>Limit</dt>
<dd>
Allow use of the directives controlling host access (<directive
module="mod_authz_host">Allow</directive>, <directive
module="mod_authz_host">Deny</directive> and <directive
module="mod_authz_host">Order</directive>).</dd>
<dt>Options[=<var>Option</var>,...]</dt>
<dd>
Allow use of the directives controlling specific directory
features (<directive module="core">Options</directive> and
<directive module="mod_include">XBitHack</directive>).
An equal sign may be given followed by a comma (but no spaces)
separated lists of options that may be set using the <directive
module="core">Options</directive> command.</dd>
</dl>
<p>Example:</p>
<example>
AllowOverride AuthConfig Indexes
</example>
<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>
<note><p>For security and performance reasons, do not set
<code>AllowOverride</code> to anything other than <code>None</code>
in your <code>&lt;Directory /&gt;</code> block. Instead, find (or
create) the <code>&lt;Directory&gt;</code> block that refers to the
directory where you're actually planning to place a
<code>.htaccess</code> file.</p>
</note>
</usage>
<seealso><directive module="core">AccessFileName</directive></seealso>
<seealso><a href="../configuring.html">Configuration Files</a></seealso>
<seealso><a href="../howto/htaccess.html">.htaccess Files</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>CGIMapExtension</name>
<description>Technique for locating the interpreter for CGI
scripts</description>
<syntax>CGIMapExtension <var>cgi-path</var> <var>.extension</var></syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<compatibility>NetWare only</compatibility>
<usage>
<p>This directive is used to control how Apache httpd finds the
interpreter used to run CGI scripts. For example, setting
<code>CGIMapExtension sys:\foo.nlm .foo</code> will
cause all CGI script files with a <code>.foo</code> extension to
be passed to the FOO interpreter.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ContentDigest</name>
<description>Enables the generation of <code>Content-MD5</code> HTTP Response
headers</description>
<syntax>ContentDigest On|Off</syntax>
<default>ContentDigest Off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>Options</override>
<status>Experimental</status>
<usage>
<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>
<example>
Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==
</example>
<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 <module>core</module>, and not by any module. For example,
SSI documents, output from CGI scripts, and byte range responses
do not have this header.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>DefaultType</name>
<description>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.
</description>
<syntax>DefaultType <var>media-type|none</var></syntax>
<default>DefaultType none</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<compatibility>The argument <code>none</code> is available in Apache httpd 2.2.7 and later. All other choices are DISABLED for 2.3.x and later.</compatibility>
<usage>
<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>
<example>
DefaultType None
</example>
<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
<directive module="mod_mime">AddType</directive> to configure media
type assignments via file extensions, or the
<directive module="core">ForceType</directive> 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>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>Define</name>
<description>Define the existence of a variable</description>
<syntax>Define <var>parameter-name</var></syntax>
<contextlist><context>server config</context></contextlist>
<usage>
<p>Equivalent to passing the <code>-D</code> argument to <program
>httpd</program>.</p>
<p>This directive can be used to toggle the use of <directive module="core"
type="section">IfDefine</directive> sections without needing to alter
<code>-D</code> arguments in any startup scripts.</p>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Directory</name>
<description>Enclose a group of directives that apply only to the
named file-system directory, sub-directories, and their contents.</description>
<syntax>&lt;Directory <var>directory-path</var>&gt;
... &lt;/Directory&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p><directive type="section">Directory</directive> and
<code>&lt;/Directory&gt;</code> are used to enclose a group of
directives that will apply only to the named directory,
sub-directories of that directory, and the files within the respective
directories. 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>&lt;Directory
/*/public_html&gt;</code> will not match
<code>/home/user/public_html</code>, but <code>&lt;Directory
/home/*/public_html&gt;</code> will match. Example:</p>
<example>
&lt;Directory /usr/local/httpd/htdocs&gt;<br />
<indent>
Options Indexes FollowSymLinks<br />
</indent>
&lt;/Directory&gt;
</example>
<note>
<p>Be careful with the <var>directory-path</var> arguments:
They have to literally match the filesystem path which Apache httpd uses
to access the files. Directives applied to a particular
<code>&lt;Directory&gt;</code> will not apply to files accessed from
that same directory via a different path, such as via different symbolic
links.</p>
</note>
<p><glossary ref="regex">Regular
expressions</glossary> can also be used, with the addition of the
<code>~</code> character. For example:</p>
<example>
&lt;Directory ~ "^/www/.*/[0-9]{3}"&gt;
</example>
<p>would match directories in <code>/www/</code> that consisted of
three numbers.</p>
<p>If multiple (non-regular expression) <directive
type="section">Directory</directive> 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>
<example>
&lt;Directory /&gt;<br />
<indent>
AllowOverride None<br />
</indent>
&lt;/Directory&gt;<br />
<br />
&lt;Directory /home/&gt;<br />
<indent>
AllowOverride FileInfo<br />
</indent>
&lt;/Directory&gt;
</example>
<p>for access to the document <code>/home/web/dir/doc.html</code>
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
<code>/home/.htaccess</code>, <code>/home/web/.htaccess</code> and
<code>/home/web/dir/.htaccess</code> in that order.</li>
</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>
<example>
&lt;Directory ~ abc$&gt;<br />
<indent>
# ... directives here ...<br />
</indent>
&lt;/Directory&gt;
</example>
<p>the regular expression section won't be considered until after
all normal <directive type="section">Directory</directive>s and
<code>.htaccess</code> files have been applied. Then the regular
expression will match on <code>/home/abc/public_html/abc</code> and
the corresponding <directive type="section">Directory</directive> will
be applied.</p>
<p><strong>Note that the default access for
<code>&lt;Directory /&gt;</code> is <code>Allow from All</code>.
This means that Apache httpd will serve any file mapped from an URL. It is
recommended that you change this with a block such
as</strong></p>
<example>
&lt;Directory /&gt;<br />
<indent>
Order Deny,Allow<br />
Deny from All<br />
</indent>
&lt;/Directory&gt;
</example>
<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>
<p>The directory sections occur in the <code>httpd.conf</code> file.
<directive type="section">Directory</directive> directives
cannot nest, and cannot appear in a <directive module="core"
type="section">Limit</directive> or <directive module="core"
type="section">LimitExcept</directive> section.</p>
</usage>
<seealso><a href="../sections.html">How &lt;Directory&gt;,
&lt;Location&gt; and &lt;Files&gt; sections work</a> for an
explanation of how these different sections are combined when a
request is received</seealso>
</directivesynopsis>
<directivesynopsis type="section">
<name>DirectoryMatch</name>
<description>Enclose directives that apply to
the contents of file-system directories matching a regular expression.</description>
<syntax>&lt;DirectoryMatch <var>regex</var>&gt;
... &lt;/DirectoryMatch&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p><directive type="section">DirectoryMatch</directive> and
<code>&lt;/DirectoryMatch&gt;</code> are used to enclose a group
of directives which will apply only to the named directory (and the files within),
the same as <directive module="core" type="section">Directory</directive>.
However, it takes as an argument a
<glossary ref="regex">regular expression</glossary>. For example:</p>
<example>
&lt;DirectoryMatch "^/www/(.+/)?[0-9]{3}"&gt;
</example>
<p>would match directories in <code>/www/</code> that consisted of three
numbers.</p>
<note><title>Compatability</title>
Prior to 2.3.9, this directive implicitly applied to sub-directories
(like <directive module="core" type="section">Directory</directive>) and
could not match the end of line symbol ($). In 2.3.9 and later,
only directories that match the expression are affected by the enclosed
directives.
</note>
<note><title>Trailing Slash</title>
This directive applies to requests for directories that may or may
not end in a trailing slash, so expressions that are anchored to the
end of line ($) must be written with care.
</note>
</usage>
<seealso><directive type="section" module="core">Directory</directive> for
a description of how regular expressions are mixed in with normal
<directive type="section">Directory</directive>s</seealso>
<seealso><a
href="../sections.html">How &lt;Directory&gt;, &lt;Location&gt; and
&lt;Files&gt; sections work</a> for an explanation of how these different
sections are combined when a request is received</seealso>
</directivesynopsis>
<directivesynopsis>
<name>DocumentRoot</name>
<description>Directory that forms the main document tree visible
from the web</description>
<syntax>DocumentRoot <var>directory-path</var></syntax>
<default>DocumentRoot /usr/local/apache/htdocs</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>This directive sets the directory from which <program>httpd</program>
will serve files. Unless matched by a directive like <directive
module="mod_alias">Alias</directive>, the server appends the
path from the requested URL to the document root to make the
path to the document. Example:</p>
<example>
DocumentRoot /usr/web
</example>
<p>then an access to
<code>http://www.my.host.com/index.html</code> refers to
<code>/usr/web/index.html</code>. If the <var>directory-path</var> is
not absolute then it is assumed to be relative to the <directive
module="core">ServerRoot</directive>.</p>
<p>The <directive>DocumentRoot</directive> should be specified without
a trailing slash.</p>
</usage>
<seealso><a href="../urlmapping.html#documentroot">Mapping URLs to Filesystem
Locations</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>EnableMMAP</name>
<description>Use memory-mapping to read files during delivery</description>
<syntax>EnableMMAP On|Off</syntax>
<default>EnableMMAP On</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<usage>
<p>This directive controls whether the <program>httpd</program> 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 <module>mod_include</module> -- Apache httpd
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
performance of the <program>httpd</program>.</li>
<li>Deleting or truncating a file while <program>httpd</program>
has it memory-mapped can cause <program>httpd</program> 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>
<example>
EnableMMAP Off
</example>
<p>For NFS mounted files, this feature may be disabled explicitly for
the offending files by specifying:</p>
<example>
&lt;Directory "/path-to-nfs-files"&gt;
<indent>
EnableMMAP Off
</indent>
&lt;/Directory&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>EnableSendfile</name>
<description>Use the kernel sendfile support to deliver files to the client</description>
<syntax>EnableSendfile On|Off</syntax>
<default>EnableSendfile Off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<compatibility>Available in version 2.0.44 and later. Default changed to Off in
version 2.3.9.</compatibility>
<usage>
<p>This directive controls whether <program>httpd</program> 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 httpd 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 <directive
module="core">DocumentRoot</directive> (e.g., NFS, SMB, CIFS, FUSE),
the kernel may be unable to serve the network file through
its own cache.</li>
</ul>
<p>For server configurations that are not vulnerable to these problems,
you may enable this feature by specifying:</p>
<example>
EnableSendfile On
</example>
<p>For network mounted files, this feature may be disabled explicitly
for the offending files by specifying:</p>
<example>
&lt;Directory "/path-to-nfs-files"&gt;
<indent>
EnableSendfile Off
</indent>
&lt;/Directory&gt;
</example>
<p>Please note that the per-directory and .htaccess configuration
of <directive>EnableSendfile</directive> is not supported by
<module>mod_cache_disk</module>.
Only global definition of <directive>EnableSendfile</directive>
is taken into account by the module.
</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>Error</name>
<description>Abort configuration parsing with a custom error message</description>
<syntax>Error <var>message</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<compatibility>2.3.9 and later</compatibility>
<usage>
<p>If an error can be detected within the configuration, this
directive can be used to generate a custom error message, and halt
configuration parsing. The typical use is for reporting required
modules which are missing from the configuration.</p>
<example><title>Example</title>
# ensure that mod_include is loaded<br />
&lt;IfModule !include_module&gt;<br />
Error mod_include is required by mod_foo. Load it with LoadModule.<br />
&lt;/IfModule&gt;<br />
<br />
# ensure that exactly one of SSL,NOSSL is defined<br />
&lt;IfDefine SSL&gt;<br />
&lt;IfDefine NOSSL&gt;<br />
Error Both SSL and NOSSL are defined. Define only one of them.<br />
&lt;/IfDefine&gt;<br />
&lt;/IfDefine&gt;<br />
&lt;IfDefine !SSL&gt;<br />
&lt;IfDefine !NOSSL&gt;<br />
Error Either SSL or NOSSL must be defined.<br />
&lt;/IfDefine&gt;<br />
&lt;/IfDefine&gt;<br />
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ErrorDocument</name>
<description>What the server will return to the client
in case of an error</description>
<syntax>ErrorDocument <var>error-code</var> <var>document</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<usage>
<p>In the event of a problem or error, Apache httpd 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
problem/error</li>
<li>redirect to an external <var>URL</var> to handle the
problem/error</li>
</ol>
<p>The first option is the default, while options 2-4 are
configured using the <directive>ErrorDocument</directive>
directive, which is followed by the HTTP response code and a URL
or a message. Apache httpd will sometimes offer additional information
regarding the problem/error.</p>
<p>URLs can begin with a slash (/) for local web-paths (relative
to the <directive module="core">DocumentRoot</directive>), or be a
full URL which the client can resolve. Alternatively, a message
can be provided to be displayed by the browser. Examples:</p>
<example>
ErrorDocument 500 http://foo.example.com/cgi-bin/tester<br />
ErrorDocument 404 /cgi-bin/bad_urls.pl<br />
ErrorDocument 401 /subscription_info.html<br />
ErrorDocument 403 "Sorry can't allow you access today"
</example>
<p>Additionally, the special value <code>default</code> can be used
to specify Apache httpd's simple hardcoded message. While not required
under normal circumstances, <code>default</code> will restore
Apache httpd's simple hardcoded message for configurations that would
otherwise inherit an existing <directive>ErrorDocument</directive>.</p>
<example>
ErrorDocument 404 /cgi-bin/bad_urls.pl<br /><br />
&lt;Directory /web/docs&gt;<br />
<indent>
ErrorDocument 404 default<br />
</indent>
&lt;/Directory&gt;
</example>
<p>Note that when you specify an <directive>ErrorDocument</directive>
that points to a remote URL (ie. anything with a method such as
<code>http</code> in front of it), Apache HTTP Server 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 <directive module="core">ErrorDocument</directive>. 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>If you are using mod_proxy, you may wish to enable
<directive module="mod_proxy">ProxyErrorOverride</directive> so that you can provide
custom error messages on behalf of your Origin servers. If you don't enable ProxyErrorOverride,
Apache httpd will not generate custom error documents for proxied content.</p>
</usage>
<seealso><a href="../custom-error.html">documentation of
customizable responses</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ErrorLog</name>
<description>Location where the server will log errors</description>
<syntax> ErrorLog <var>file-path</var>|syslog[:<var>facility</var>]</syntax>
<default>ErrorLog logs/error_log (Unix) ErrorLog logs/error.log (Windows and OS/2)</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ErrorLog</directive> 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 <directive module="core">ServerRoot</directive>.</p>
<example><title>Example</title>
ErrorLog /var/log/httpd/error_log
</example>
<p>If the <var>file-path</var>
begins with a pipe character "<code>|</code>" then it is assumed to be a
command to spawn to handle the error log.</p>
<example><title>Example</title>
ErrorLog "|/usr/local/bin/httpd_errors"
</example>
<p>See the notes on <a href="../logs.html#piped">piped logs</a> for
more information.</p>
<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). The facility is effectively global, and if it is changed
in individual virtual hosts, the final facility specified affects the
entire server.</p>
<example><title>Example</title>
ErrorLog syslog:user
</example>
<p>SECURITY: See the <a
href="../misc/security_tips.html#serverroot">security tips</a>
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>
<note type="warning"><title>Note</title>
<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>
</note>
</usage>
<seealso><directive module="core">LogLevel</directive></seealso>
<seealso><a href="../logs.html">Apache HTTP Server Log Files</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ErrorLogFormat</name>
<description>Format specification for error log entries</description>
<syntax> ErrorLog [connection|request] <var>format</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Available in Apache httpd 2.3.9 and later</compatibility>
<usage>
<p><directive>ErrorLogFormat</directive> allows to specify what
supplementary information is logged in the error log in addition to the
actual log message.</p>
<example><title>Simple example</title>
ErrorLogFormat "[%t] [%l] [pid %P] %F: %E: [client %a] %M"
</example>
<p>Specifying <code>connection</code> or <code>request</code> as first
paramter allows to specify additional formats, causing additional
information to be logged when the first message is logged for a specific
connection or request, respectivly. This additional information is only
logged once per connection/request. If a connection or request is processed
without causing any log message, the additional information is not logged
either.</p>
<p>It can happen that some format string items do not produce output. For
example, the Referer header is only present if the log message is
associated to a request and the log message happens at a time when the
Referer header has already been read from the client. If no output is
produced, the default behaviour is to delete everything from the preceeding
space character to the next space character. This means the log line is
implicitly divided into fields on non-whitespace to whitespace transitions.
If a format string item does not produce output, the whole field is
ommitted. For example, if the remote address <code>%a</code> in the log
format <code>[%t] [%l] [%a] %M&nbsp;</code> is not available, the surrounding
brackets are not logged either. Space characters can be escaped with a
backslash to prevent them from delimiting a field. The combination '%&nbsp;'
(percent space) is a zero-witdh field delimiter that does not produce any
output.</p>
<p>The above behaviour can be changed by adding modifiers to the format
string item. A <code>-</code> (minus) modifier causes a minus to be logged if the
respective item does not produce any output. In once-per-connection/request
formats, it is also possible to use the <code>+</code> (plus) modifier. If an
item with the plus modifier does not produce any output, the whole line is
ommitted.</p>
<p>A number as modifier can be used to assign a log severity level to a
format item. The item will only be logged if the severity of the log
message is not higher than the specified log severity level. The number can
range from 1 (alert) over 4 (warn) and 7 (debug) to 15 (trace8).</p>
<p>Some format string items accept additional parameters in braces.</p>
<table border="1" style="zebra">
<columnspec><column width=".2"/><column width=".8"/></columnspec>
<tr><th>Format&nbsp;String</th> <th>Description</th></tr>
<tr><td><code>%%</code></td>
<td>The percent sign</td></tr>
<tr><td><code>%...a</code></td>
<td>Remote IP-address and port</td></tr>
<tr><td><code>%...A</code></td>
<td>Local IP-address and port</td></tr>
<tr><td><code>%...{name}e</code></td>
<td>Request environment variable <code>name</code></td></tr>
<tr><td><code>%...E</code></td>
<td>APR/OS error status code and string</td></tr>
<tr><td><code>%...F</code></td>
<td>Source file name and line number of the log call</td></tr>
<tr><td><code>%...{name}i</code></td>
<td>Request header <code>name</code></td></tr>
<tr><td><code>%...k</code></td>
<td>Number of keep-alive requests on this connection</td></tr>
<tr><td><code>%...l</code></td>
<td>Loglevel of the message</td></tr>
<tr><td><code>%...L</code></td>
<td>Log ID of the request</td></tr>
<tr><td><code>%...{c}L</code></td>
<td>Log ID of the connection</td></tr>
<tr><td><code>%...{C}L</code></td>
<td>Log ID of the connection if used in connection scope, empty otherwise</td></tr>
<tr><td><code>%...m</code></td>
<td>Name of the module logging the message</td></tr>
<tr><td><code>%M</code></td>
<td>The actual log message</td></tr>
<tr><td><code>%...{name}n</code></td>
<td>Request note <code>name</code></td></tr>
<tr><td><code>%...P</code></td>
<td>Process ID of current process</td></tr>
<tr><td><code>%...T</code></td>
<td>Thread ID of current thread</td></tr>
<tr><td><code>%...t</code></td>
<td>The current time</td></tr>
<tr><td><code>%...{u}t</code></td>
<td>The current time including micro-seconds</td></tr>
<tr><td><code>%...{cu}t</code></td>
<td>The current time in compact ISO 8601 format, including
micro-seconds</td></tr>
<tr><td><code>%...v</code></td>
<td>The canonical <directive module="core">ServerName</directive>
of the current server.</td></tr>
<tr><td><code>%...V</code></td>
<td>The server name of the server serving the request according to the
<directive module="core" >UseCanonicalName</directive>
setting.</td></tr>
<tr><td><code>\&nbsp;</code> (backslash space)</td>
<td>Non-field delimiting space</td></tr>
<tr><td><code>%&nbsp;</code> (percent space)</td>
<td>Field delimiter (no output)</td></tr>
</table>
<p>The log ID format <code>%L</code> produces a unique id for a connection
or request. This can be used to correlate which log lines belong to the
same connection or request, which request happens on which connection.
A <code>%L</code> format string is also available in
<module>mod_log_config</module>, to allow to correlate access log entries
with error log lines. If <module>mod_unique_id</module> is loaded, its
unique id will be used as log ID for requests.</p>
<example><title>Example (somewhat similar to default format)</title>
ErrorLogFormat "[%{u}t] [%-m:%l] [pid %P] %7F: %E: [client\ %a]
%M%&nbsp;,\&nbsp;referer\&nbsp;%{Referer}i"
</example>
<example><title>Example (similar to the 2.2.x format)</title>
ErrorLogFormat "[%t] [%l] %7F: %E: [client\ %a]
%M%&nbsp;,\&nbsp;referer\&nbsp;%{Referer}i"
</example>
<example><title>Advanced example with request/connection log IDs</title>
ErrorLogFormat "[%{uc}t] [%-m:%-l] [R:%L] [C:%{C}L] %7F: %E: %M"<br/>
ErrorLogFormat request "[%{uc}t] [R:%L] Request %k on C:%{c}L pid:%P tid:%T"<br/>
ErrorLogFormat request "[%{uc}t] [R:%L] UA:'%+{User-Agent}i'"<br/>
ErrorLogFormat request "[%{uc}t] [R:%L] Referer:'%+{Referer}i'"<br/>
ErrorLogFormat connection "[%{uc}t] [C:%{c}L] local\ %a remote\ %A"<br/>
</example>
</usage>
<seealso><directive module="core">ErrorLog</directive></seealso>
<seealso><directive module="core">LogLevel</directive></seealso>
<seealso><a href="../logs.html">Apache HTTP Server Log Files</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ExtendedStatus</name>
<description>Keep track of extended status information for each
request</description>
<syntax>ExtendedStatus On|Off</syntax>
<default>ExtendedStatus Off[*]</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>This option tracks additional data per worker about the
currently executing request, and a utilization summary; you
can see these variables during runtime by configuring
<module>mod_status</module>. Note that other modules may
rely on this scoreboard.</p>
<p>This setting applies to the entire server, and cannot be
enabled or disabled on a virtualhost-by-virtualhost basis.
The collection of extended status information can slow down
the server. Also note that this setting cannot be changed
during a graceful restart.</p>
<note>
<p>Note that loading <module>mod_status</module> will change
the default behavior to ExtendedStatus On, while other
third party modules may do the same. Such modules rely on
collecting detailed information about the state of all workers.
The default is changed by <module>mod_status</module> beginning
with version 2.3.6; the previous default was always Off.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>FileETag</name>
<description>File attributes used to create the ETag
HTTP response header for static files</description>
<syntax>FileETag <var>component</var> ...</syntax>
<default>FileETag INode MTime Size</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<usage>
<p>
The <directive>FileETag</directive> 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 static file.
(The <code>ETag</code> value is used in cache management to save
network bandwidth.) The
<directive>FileETag</directive> 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:
<example>FileETag INode MTime Size</example></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&nbsp;INode&nbsp;MTime&nbsp;Size</code>, and a
subdirectory's includes <code>FileETag&nbsp;-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&nbsp;MTime&nbsp;Size</code>.</p>
<note type="warning"><title>Warning</title>
Do not change the default for directories or locations that have WebDAV
enabled and use <module>mod_dav_fs</module> as a storage provider.
<module>mod_dav_fs</module> uses <code>INode&nbsp;MTime&nbsp;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 <directive>FileETag</directive>.
</note>
<note><title>Server Side Includes</title>
An ETag is not generated for responses parsed by <module>mod_include</module>,
since the response entity can change without a change of the INode, MTime, or Size
of the static file with embedded SSI directives.
</note>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Files</name>
<description>Contains directives that apply to matched
filenames</description>
<syntax>&lt;Files <var>filename</var>&gt; ... &lt;/Files&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <directive type="section">Files</directive> directive
limits the scope of the enclosed directives by filename. It is comparable
to the <directive module="core" type="section">Directory</directive>
and <directive module="core" type="section">Location</directive>
directives. It should be matched with a <code>&lt;/Files&gt;</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. <directive type="section">Files</directive>
sections are processed in the order they appear in the
configuration file, after the <directive module="core"
type="section">Directory</directive> sections and
<code>.htaccess</code> files are read, but before <directive
type="section" module="core">Location</directive> sections. Note
that <directive type="section">Files</directive> can be nested
inside <directive type="section"
module="core">Directory</directive> 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.
<glossary ref="regex">Regular expressions</glossary>
can also be used, with the addition of the
<code>~</code> character. For example:</p>
<example>
&lt;Files ~ "\.(gif|jpe?g|png)$"&gt;
</example>
<p>would match most common Internet graphics formats. <directive
module="core" type="section">FilesMatch</directive> is preferred,
however.</p>
<p>Note that unlike <directive type="section"
module="core">Directory</directive> and <directive type="section"
module="core">Location</directive> sections, <directive
type="section">Files</directive> 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>
</usage>
<seealso><a href="../sections.html">How &lt;Directory&gt;, &lt;Location&gt;
and &lt;Files&gt; sections work</a> for an explanation of how these
different sections are combined when a request is received</seealso>
</directivesynopsis>
<directivesynopsis type="section">
<name>FilesMatch</name>
<description>Contains directives that apply to regular-expression matched
filenames</description>
<syntax>&lt;FilesMatch <var>regex</var>&gt; ... &lt;/FilesMatch&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <directive type="section">FilesMatch</directive> directive
limits the scope of the enclosed directives by filename, just as the
<directive module="core" type="section">Files</directive> directive
does. However, it accepts a <glossary ref="regex">regular
expression</glossary>. For example:</p>
<example>
&lt;FilesMatch "\.(gif|jpe?g|png)$"&gt;
</example>
<p>would match most common Internet graphics formats.</p>
</usage>
<seealso><a href="../sections.html">How &lt;Directory&gt;, &lt;Location&gt;
and &lt;Files&gt; sections work</a> for an explanation of how these
different sections are combined when a request is received</seealso>
</directivesynopsis>
<directivesynopsis>
<name>ForceType</name>
<description>Forces all matching files to be served with the specified
media type in the HTTP Content-Type header field</description>
<syntax>ForceType <var>media-type</var>|None</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<compatibility>Moved to the core in Apache httpd 2.0</compatibility>
<usage>
<p>When placed into an <code>.htaccess</code> file or a
<directive type="section" module="core">Directory</directive>, or
<directive type="section" module="core">Location</directive> or
<directive type="section" module="core">Files</directive>
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>
<example>
ForceType image/gif
</example>
<p>Note that this directive overrides other indirect media type
associations defined in mime.types or via the
<directive module="mod_mime">AddType</directive>.</p>
<p>You can also override more general
<directive>ForceType</directive> settings
by using the value of <code>None</code>:</p>
<example>
# force all files to be image/gif:<br />
&lt;Location /images&gt;<br />
<indent>
ForceType image/gif<br />
</indent>
&lt;/Location&gt;<br />
<br />
# but normal mime-type associations here:<br />
&lt;Location /images/mixed&gt;<br />
<indent>
ForceType None<br />
</indent>
&lt;/Location&gt;
</example>
<p>This directive primarily overrides the content types generated for
static files served out of the filesystem. For resources other than
static files, where the generator of the response typically specifies
a Content-Type, this directive has no effect.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>GprofDir</name>
<description>Directory to write gmon.out profiling data to. </description>
<syntax>GprofDir <var>/tmp/gprof/</var>|<var>/tmp/gprof/</var>%</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>When the server has been compiled with gprof profiling support,
<directive>GprofDir</directive> causes <code>gmon.out</code> files to
be written to the specified directory when the process exits. If the
argument ends with a percent symbol ('%'), subdirectories are created
for each process id.</p>
<p>This directive currently only works with the <module>prefork</module>
MPM.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>HostnameLookups</name>
<description>Enables DNS lookups on client IP addresses</description>
<syntax>HostnameLookups On|Off|Double</syntax>
<default>HostnameLookups Off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context></contextlist>
<usage>
<p>This directive enables DNS lookups so that host names can be
logged (and passed to CGIs/SSIs in <code>REMOTE_HOST</code>).
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 <module>mod_authz_host</module> 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 <program>logresolve</program>, 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>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>If</name>
<description>Contains directives that apply only if a condition is
satisfied by a request at runtime</description>
<syntax>&lt;If <var>expression</var>&gt; ... &lt;/If&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <directive type="section">If</directive> directive
evaluates an expression at runtime, and applies the enclosed
directives if and only if the expression evaluates to true.
For example:</p>
<example>
&lt;If "$req{Host} = ''"&gt;
</example>
<p>would match HTTP/1.0 requests without a <var>Host:</var> header.</p>
<p>You may compare the value of any variable in the request headers
($req), response headers ($resp) or environment ($env) in your
expression.</p>
<p>Apart from <code>=</code>, <code>If</code> can use the <code>IN</code>
operator to compare if the expression is in a given range:</p>
<example>
&lt;If %{REQUEST_METHOD} IN GET,HEAD,OPTIONS&gt;
</example>
</usage>
<seealso><a href="../expr.html">Expressions in Apache HTTP Server</a>,
for a complete reference and more examples.</seealso>
<seealso><a href="../sections.html">How &lt;Directory&gt;, &lt;Location&gt;,
&lt;Files&gt; sections work</a> for an explanation of how these
different sections are combined when a request is received.
<directive type="section">If</directive> has the same precedence
and usage as <directive type="section">Files</directive></seealso>
</directivesynopsis>
<directivesynopsis type="section">
<name>IfDefine</name>
<description>Encloses directives that will be processed only
if a test is true at startup</description>
<syntax>&lt;IfDefine [!]<var>parameter-name</var>&gt; ...
&lt;/IfDefine&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <code>&lt;IfDefine <var>test</var>&gt;...&lt;/IfDefine&gt;
</code> section is used to mark directives that are conditional. The
directives within an <directive type="section">IfDefine</directive>
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 <directive type="section"
>IfDefine</directive> 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
<program>httpd</program> command line via <code>-D<var>parameter</var>
</code> at the time the server was started or by the <directive
module="core">Define</directive> directive.</p>
<p><directive type="section">IfDefine</directive> sections are
nest-able, which can be used to implement simple
multiple-parameter tests. Example:</p>
<example>
httpd -DReverseProxy -DUseCache -DMemCache ...<br />
<br />
# httpd.conf<br />
&lt;IfDefine ReverseProxy&gt;<br />
<indent>
LoadModule proxy_module modules/mod_proxy.so<br />
LoadModule proxy_http_module modules/mod_proxy_http.so<br />
&lt;IfDefine UseCache&gt;<br />
<indent>
LoadModule cache_module modules/mod_cache.so<br />
&lt;IfDefine MemCache&gt;<br />
<indent>
LoadModule mem_cache_module modules/mod_mem_cache.so<br />
</indent>
&lt;/IfDefine&gt;<br />
&lt;IfDefine !MemCache&gt;<br />
<indent>
LoadModule cache_disk_module modules/mod_cache_disk.so<br />
</indent>
&lt;/IfDefine&gt;
</indent>
&lt;/IfDefine&gt;
</indent>
&lt;/IfDefine&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>IfModule</name>
<description>Encloses directives that are processed conditional on the
presence or absence of a specific module</description>
<syntax>&lt;IfModule [!]<var>module-file</var>|<var>module-identifier</var>&gt; ...
&lt;/IfModule&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<compatibility>Module identifiers are available in version 2.1 and
later.</compatibility>
<usage>
<p>The <code>&lt;IfModule <var>test</var>&gt;...&lt;/IfModule&gt;</code>
section is used to mark directives that are conditional on the presence of
a specific module. The directives within an <directive type="section"
>IfModule</directive> 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 <directive type="section"
>IfModule</directive> 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 httpd -- either compiled in or
dynamically loaded using <directive module="mod_so"
>LoadModule</directive>. 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
<code>mod_rewrite.c</code> is the file name. If a module consists of
several source files, use the name of the file containing the string
<code>STANDARD20_MODULE_STUFF</code>.</p>
<p><directive type="section">IfModule</directive> sections are
nest-able, which can be used to implement simple multiple-module
tests.</p>
<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 <directive type="section">IfModule</directive>
sections.</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>Include</name>
<description>Includes other configuration files from within
the server configuration files</description>
<syntax>Include [<var>optional</var>|<var>strict</var>] <var>file-path</var>|<var>directory-path</var>|<var>wildcard</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context>
</contextlist>
<compatibility>Wildcard matching available in 2.0.41 and later, directory
wildcard matching available in 2.3.6 and later</compatibility>
<usage>
<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
in the filename or directory parts of the path to include several files
at once, in alphabetical order. In addition, if
<directive>Include</directive> points to a directory, rather than a file,
Apache httpd 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
<program>httpd</program> 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>When a wildcard is specified for a <strong>file</strong> component of
the path, and no file matches the wildcard, the
<directive module="core">Include</directive>
directive will be <strong>silently ignored</strong>. When a wildcard is
specified for a <strong>directory</strong> component of the path, and
no directory matches the wildcard, the
<directive module="core">Include</directive> directive will
<strong>fail with an error</strong> saying the directory cannot be found.
</p>
<p>For further control over the behaviour of the server when no files or
directories match, prefix the path with the modifiers <var>optional</var>
or <var>strict</var>. If <var>optional</var> is specified, any wildcard
file or directory that does not match will be silently ignored. If
<var>strict</var> is specified, any wildcard file or directory that does
not match at least one file will cause server startup to fail.</p>
<p>When a directory or file component of the path is
specified exactly, and that directory or file does not exist,
<directive module="core">Include</directive> directive will fail with an
error saying the file or directory cannot be found.</p>
<p>The file path specified may be an absolute path, or may be relative
to the <directive module="core">ServerRoot</directive> directory.</p>
<p>Examples:</p>
<example>
Include /usr/local/apache2/conf/ssl.conf<br />
Include /usr/local/apache2/conf/vhosts/*.conf
</example>
<p>Or, providing paths relative to your <directive
module="core">ServerRoot</directive> directory:</p>
<example>
Include conf/ssl.conf<br />
Include conf/vhosts/*.conf
</example>
<p>Wildcards may be included in the directory or file portion of the
path. In the following example, the server will fail to load if no
directories match conf/vhosts/*, but will load successfully if no
files match *.conf.</p>
<example>
Include conf/vhosts/*/vhost.conf<br />
Include conf/vhosts/*/*.conf
</example>
<p>In this example, the server will fail to load if either
conf/vhosts/* matches no directories, or if *.conf matches no files:</p>
<example>
Include strict conf/vhosts/*/*.conf
</example>
<p>In this example, the server load successfully if either conf/vhosts/*
matches no directories, or if *.conf matches no files:</p>
<example>
Include optional conf/vhosts/*/*.conf
</example>
</usage>
<seealso><program>apachectl</program></seealso>
</directivesynopsis>
<directivesynopsis>
<name>KeepAlive</name>
<description>Enables HTTP persistent connections</description>
<syntax>KeepAlive On|Off</syntax>
<default>KeepAlive On</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The Keep-Alive extension to HTTP/1.0 and the persistent
connection feature of HTTP/1.1 provide long-lived HTTP sessions
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>
<p>For HTTP/1.0 clients, Keep-Alive connections will only be
used if they are specifically requested by a client. In
addition, a Keep-Alive connection with an HTTP/1.0 client can
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
generally not use Keep-Alive connections to HTTP/1.0 clients.
For HTTP/1.1 clients, persistent connections are the default
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 <directive module="mpm_common"
>MaxConnectionsPerChild</directive> directive, regardless
of how many requests are sent using the connection.</p>
</usage>
<seealso><directive module="core">MaxKeepAliveRequests</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>KeepAliveTimeout</name>
<description>Amount of time the server will wait for subsequent
requests on a persistent connection</description>
<syntax>KeepAliveTimeout <var>num</var>[ms]</syntax>
<default>KeepAliveTimeout 5</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Specifying a value in milliseconds is available in
Apache httpd 2.3.2 and later</compatibility>
<usage>
<p>The number of seconds Apache httpd 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
<directive module="core">Timeout</directive> directive applies.</p>
<p>Setting <directive>KeepAliveTimeout</directive> 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 <directive
module="core">NameVirtualHost</directive> will be used.
The other values will be ignored.</p>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Limit</name>
<description>Restrict enclosed access controls to only certain HTTP
methods</description>
<syntax>&lt;Limit <var>method</var> [<var>method</var>] ... &gt; ...
&lt;/Limit&gt;</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig, Limit</override>
<usage>
<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
<directive type="section">Limit</directive> section.</strong></p>
<p>The purpose of the <directive type="section">Limit</directive>
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 <directive
type="section">Limit</directive> 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>
<example>
&lt;Limit POST PUT DELETE&gt;<br />
<indent>
Require valid-user<br />
</indent>
&lt;/Limit&gt;
</example>
<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 <directive module="core"
>TraceEnable</directive>).</p>
<note type="warning">A <directive type="section"
module="core">LimitExcept</directive> section should always be
used in preference to a <directive type="section">Limit</directive>
section when restricting access, since a <directive type="section"
module="core">LimitExcept</directive> section provides protection
against arbitrary methods.</note>
<p>The <directive type="section">Limit</directive> and
<directive type="section" module="core">LimitExcept</directive>
directives may be nested. In this case, each successive level of
<directive type="section">Limit</directive> or <directive
type="section" module="core">LimitExcept</directive> directives must
further restrict the set of methods to which access controls apply.</p>
<note type="warning">When using
<directive type="section">Limit</directive> or
<directive type="section">LimitExcept</directive> directives with
the <directive module="mod_authz_core">Require</directive> directive,
note that the first <directive module="mod_authz_core">Require</directive>
to succeed authorizes the request, regardless of the presence of other
<directive module="mod_authz_core">Require</directive> directives.</note>
<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>
<example>
&lt;LimitExcept GET&gt;
<indent>
Require valid-user
</indent>
&lt;/LimitExcept&gt;<br />
&lt;Limit POST&gt;
<indent>
Require group editors
</indent>
&lt;/Limit&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>LimitExcept</name>
<description>Restrict access controls to all HTTP methods
except the named ones</description>
<syntax>&lt;LimitExcept <var>method</var> [<var>method</var>] ... &gt; ...
&lt;/LimitExcept&gt;</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig, Limit</override>
<usage>
<p><directive type="section">LimitExcept</directive> and
<code>&lt;/LimitExcept&gt;</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 <directive type="section"
module="core">Limit</directive> section and can be used to control
both standard and nonstandard/unrecognized methods. See the
documentation for <directive module="core"
type="section">Limit</directive> for more details.</p>
<p>For example:</p>
<example>
&lt;LimitExcept POST GET&gt;<br />
<indent>
Require valid-user<br />
</indent>
&lt;/LimitExcept&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>LimitInternalRecursion</name>
<description>Determine maximum number of internal redirects and nested
subrequests</description>
<syntax>LimitInternalRecursion <var>number</var> [<var>number</var>]</syntax>
<default>LimitInternalRecursion 10</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<compatibility>Available in Apache httpd 2.0.47 and later</compatibility>
<usage>
<p>An internal redirect happens, for example, when using the <directive
module="mod_actions">Action</directive> directive, which internally
redirects the original request to a CGI script. A subrequest is Apache httpd's
mechanism to find out what would happen for some URI if it were requested.
For example, <module>mod_dir</module> uses subrequests to look for the
files listed in the <directive module="mod_dir">DirectoryIndex</directive>
directive.</p>
<p><directive>LimitInternalRecursion</directive> 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>
<example><title>Example</title>
LimitInternalRecursion 5
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>LimitRequestBody</name>
<description>Restricts the total size of the HTTP request body sent
from the client</description>
<syntax>LimitRequestBody <var>bytes</var></syntax>
<default>LimitRequestBody 0</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>This directive specifies the number of <var>bytes</var> from 0
(meaning unlimited) to 2147483647 (2GB) that are allowed in a
request body. See the note below for the limited applicability
to proxy requests.</p>
<p>The <directive>LimitRequestBody</directive> 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>
<example>
LimitRequestBody 102400
</example>
<note><p>For a full description of how this directive is interpreted by
proxy requests, see the <module>mod_proxy</module> documentation.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>LimitRequestFields</name>
<description>Limits the number of HTTP request header fields that
will be accepted from the client</description>
<syntax>LimitRequestFields <var>number</var></syntax>
<default>LimitRequestFields 100</default>
<contextlist><context>server config</context><context>virtual host</context></contextlist>
<usage>
<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 <directive>LimitRequestFields</directive> 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>
<example>
LimitRequestFields 50
</example>
<note type="warning"><title>Warning</title>
<p> When name-based virtual hosting is used, the value for this
directive is taken from the default (first-listed) virtual host for the
<directive>NameVirtualHost</directive> the connection was mapped to.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>LimitRequestFieldSize</name>
<description>Limits the size of the HTTP request header allowed from the
client</description>
<syntax>LimitRequestFieldSize <var>bytes</var></syntax>
<default>LimitRequestFieldSize 8190</default>
<contextlist><context>server config</context><context>virtual host</context></contextlist>
<usage>
<p>This directive specifies the number of <var>bytes</var>
that will be allowed in an HTTP request header.</p>
<p>The <directive>LimitRequestFieldSize</directive> 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>
<example>
LimitRequestFieldSize 4094
</example>
<note>Under normal conditions, the value should not be changed from
the default.</note>
<note type="warning"><title>Warning</title>
<p> When name-based virtual hosting is used, the value for this
directive is taken from the default (first-listed) virtual host for the
<directive>NameVirtualHost</directive> the connection was mapped to.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>LimitRequestLine</name>
<description>Limit the size of the HTTP request line that will be accepted
from the client</description>
<syntax>LimitRequestLine <var>bytes</var></syntax>
<default>LimitRequestLine 8190</default>
<contextlist><context>server config</context><context>virtual host</context></contextlist>
<usage>
<p>This directive sets the number of <var>bytes</var> that will be
allowed on the HTTP request-line.</p>
<p>The <directive>LimitRequestLine</directive> 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
<directive>LimitRequestLine</directive> 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>
<example>
LimitRequestLine 4094
</example>
<note>Under normal conditions, the value should not be changed from
the default.</note>
<note type="warning"><title>Warning</title>
<p> When name-based virtual hosting is used, the value for this
directive is taken from the default (first-listed) virtual host for the
<directive>NameVirtualHost</directive> the connection was mapped to.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>LimitXMLRequestBody</name>
<description>Limits the size of an XML-based request body</description>
<syntax>LimitXMLRequestBody <var>bytes</var></syntax>
<default>LimitXMLRequestBody 1000000</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>All</override>
<usage>
<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>
<example>
LimitXMLRequestBody 0
</example>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Location</name>
<description>Applies the enclosed directives only to matching
URLs</description>
<syntax>&lt;Location
<var>URL-path</var>|<var>URL</var>&gt; ... &lt;/Location&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive type="section">Location</directive> directive
limits the scope of the enclosed directives by URL. It is similar to the
<directive type="section" module="core">Directory</directive>
directive, and starts a subsection which is terminated with a
<code>&lt;/Location&gt;</code> directive. <directive
type="section">Location</directive> sections are processed in the
order they appear in the configuration file, after the <directive
type="section" module="core">Directory</directive> sections and
<code>.htaccess</code> files are read, and after the <directive
type="section" module="core">Files</directive> sections.</p>
<p><directive type="section">Location</directive> sections operate
completely outside the filesystem. This has several consequences.
Most importantly, <directive type="section">Location</directive>
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>
<p>The enclosed directives will be applied to the request if the path component
of the URL meets <em>any</em> of the following criteria:
</p>
<ul>
<li>The specified location matches exactly the path component of the URL.
</li>
<li>The specified location, which ends in a forward slash, is a prefix
of the path component of the URL (treated as a context root).
</li>
<li>The specified location, with the addition of a trailing slash, is a
prefix of the path component of the URL (also treated as a context root).
</li>
</ul>
<p>
In the example below, where no trailing slash is used, requests to
/private1, /private1/ and /private1/file.txt will have the enclosed
directives applied, but /private1other would not.
</p>
<example>
&lt;Location /private1&gt;
...
</example>
<p>
In the example below, where a trailing slash is used, requests to
/private2/ and /private2/file.txt will have the enclosed
directives applied, but /private2 and /private2other would not.
</p>
<example>
&lt;Location /private2<em>/</em>&gt;
...
</example>
<note><title>When to use <directive
type="section">Location</directive></title>
<p>Use <directive type="section">Location</directive> to apply
directives to content that lives outside the filesystem. For
content that lives in the filesystem, use <directive
type="section" module="core">Directory</directive> and <directive
type="section" module="core">Files</directive>. An exception is
<code>&lt;Location /&gt;</code>, which is an easy way to
apply a configuration to the entire server.</p>
</note>
<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
<code>scheme://servername/path</code>, and you must include the
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>
<p><glossary ref="regex">Regular expressions</glossary>
can also be used, with the addition of the <code>~</code>
character. For example:</p>
<example>
&lt;Location ~ "/(extra|special)/data"&gt;
</example>
<p>would match URLs that contained the substring <code>/extra/data</code>
or <code>/special/data</code>. The directive <directive
type="section" module="core">LocationMatch</directive> behaves
identical to the regex version of <directive
type="section">Location</directive>, and is preferred, for the
simple reason that <code>~</code> is hard to distinguish from
<code>-</code> in many fonts.</p>
<p>The <directive type="section">Location</directive>
functionality is especially useful when combined with the
<directive module="core">SetHandler</directive>
directive. For example, to enable status requests, but allow them
only from browsers at <code>example.com</code>, you might use:</p>
<example>
&lt;Location /status&gt;<br />
<indent>
SetHandler server-status<br />
Require host example.com<br />
</indent>
&lt;/Location&gt;
</example>
<note><title>Note about / (slash)</title>
<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
slash (<em>i.e.</em>, <code>/home///foo</code> is the same as
<code>/home/foo</code>). In URL-space this is not necessarily true.
The <directive type="section" module="core">LocationMatch</directive>
directive and the regex version of <directive type="section"
>Location</directive> require you to explicitly specify multiple
slashes if that is your intention.</p>
<p>For example, <code>&lt;LocationMatch ^/abc&gt;</code> would match
the request URL <code>/abc</code> but not the request URL <code>
//abc</code>. The (non-regex) <directive type="section"
>Location</directive> directive behaves similarly when used for
proxy requests. But when (non-regex) <directive type="section"
>Location</directive> is used for non-proxy requests it will
implicitly match multiple slashes with a single slash. For example,
if you specify <code>&lt;Location /abc/def&gt;</code> and the
request is to <code>/abc//def</code> then it will match.</p>
</note>
</usage>
<seealso><a href="../sections.html">How &lt;Directory&gt;, &lt;Location&gt;
and &lt;Files&gt; sections work</a> for an explanation of how these
different sections are combined when a request is received.</seealso>
<seealso><directive module="core">LocationMatch</directive></seealso>
</directivesynopsis>
<directivesynopsis type="section">
<name>LocationMatch</name>
<description>Applies the enclosed directives only to regular-expression
matching URLs</description>
<syntax>&lt;LocationMatch
<var>regex</var>&gt; ... &lt;/LocationMatch&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive type="section">LocationMatch</directive> directive
limits the scope of the enclosed directives by URL, in an identical manner
to <directive module="core" type="section">Location</directive>. However,
it takes a <glossary ref="regex">regular expression</glossary>
as an argument instead of a simple string. For example:</p>
<example>
&lt;LocationMatch "/(extra|special)/data"&gt;
</example>
<p>would match URLs that contained the substring <code>/extra/data</code>
or <code>/special/data</code>.</p>
</usage>
<seealso><a href="../sections.html">How &lt;Directory&gt;, &lt;Location&gt;
and &lt;Files&gt; sections work</a> for an explanation of how these
different sections are combined when a request is received</seealso>
</directivesynopsis>
<directivesynopsis>
<name>LogLevel</name>
<description>Controls the verbosity of the ErrorLog</description>
<syntax>LogLevel [<var>module</var>:]<var>level</var>
[<var>module</var>:<var>level</var>] ...
</syntax>
<default>LogLevel warn</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context>
</contextlist>
<compatibility>Per-module and per-directory configuration is available in
Apache HTTP Server 2.3.6 and later</compatibility>
<usage>
<p><directive>LogLevel</directive> adjusts the verbosity of the
messages recorded in the error logs (see <directive
module="core">ErrorLog</directive> directive). The following
<var>level</var>s are available, in order of decreasing
significance:</p>
<table border="1">
<columnspec><column width=".2"/><column width=".3"/><column width=".5"/>
</columnspec>
<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
StartServers, or Min/MaxSpareServers)..."</td>
</tr>
<tr>
<td><code>debug</code> </td>
<td>Debug-level messages</td>
<td>"Opening config file ..."</td>
</tr>
<tr>
<td><code>trace1</code> </td>
<td>Trace messages</td>
<td>"proxy: FTP: control connection complete"</td>
</tr>
<tr>
<td><code>trace2</code> </td>
<td>Trace messages</td>
<td>"proxy: CONNECT: sending the CONNECT request to the remote proxy"</td>
</tr>
<tr>
<td><code>trace3</code> </td>
<td>Trace messages</td>
<td>"openssl: Handshake: start"</td>
</tr>
<tr>
<td><code>trace4</code> </td>
<td>Trace messages</td>
<td>"read from buffered SSL brigade, mode 0, 17 bytes"</td>
</tr>
<tr>
<td><code>trace5</code> </td>
<td>Trace messages</td>
<td>"map lookup FAILED: map=rewritemap key=keyname"</td>
</tr>
<tr>
<td><code>trace6</code> </td>
<td>Trace messages</td>
<td>"cache lookup FAILED, forcing new map lookup"</td>
</tr>
<tr>
<td><code>trace7</code> </td>
<td>Trace messages, dumping large amounts of data</td>
<td>"| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |"</td>
</tr>
<tr>
<td><code>trace8</code> </td>
<td>Trace messages, dumping large amounts of data</td>
<td>"| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |"</td>
</tr>
</table>
<p>When a particular level is specified, messages from all
other levels of higher significance will be reported as well.
<em>E.g.</em>, when <code>LogLevel info</code> is specified,
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>
<example>
LogLevel notice
</example>
<note><title>Note</title>
<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>
</note>
<p>Specifying a level without a module name will reset the level
for all modules to that level. Specifying a level with a module
name will set the level for that module only. It is possible to
use the module source file name, the module identifier, or the
module identifier with the trailing <code>_module</code> omitted
as module specification. This means the following three specifications
are equivalent:</p>
<example>
LogLevel info ssl:warn<br />
LogLevel info mod_ssl.c:warn<br />
LogLevel info ssl_module:warn<br />
</example>
<p>It is also possible to change the level per directory:</p>
<example>
LogLevel info<br />
&lt;Directory /usr/local/apache/htdocs/app&gt;<br />
&nbsp; LogLevel debug<br />
&lt;/Files&gt;
</example>
<note>
Per directory loglevel configuration only affects messages that are
logged after the request has been parsed and that are associated with
the request. Log messages which are associated with the connection or
the server are not affected.
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>MaxKeepAliveRequests</name>
<description>Number of requests allowed on a persistent
connection</description>
<syntax>MaxKeepAliveRequests <var>number</var></syntax>
<default>MaxKeepAliveRequests 100</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>MaxKeepAliveRequests</directive> directive
limits the number of requests allowed per connection when
<directive module="core" >KeepAlive</directive> 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>
<example>
MaxKeepAliveRequests 500
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>Mutex</name>
<description>Configures mutex mechanism and lock file directory for all
or specified mutexes</description>
<syntax>Mutex <var>mechanism</var> [default|<var>mutex-name</var>] ... [OmitPID]</syntax>
<default>Mutex default</default>
<contextlist><context>server config</context></contextlist>
<compatibility>Available in Apache HTTP Server 2.3.4 and later</compatibility>
<usage>
<p>The <directive>Mutex</directive> directive sets the mechanism,
and optionally the lock file location, that httpd and modules use
to serialize access to resources. Specify <code>default</code> as
the first argument to change the settings for all mutexes; specify
a mutex name (see table below) as the first argument to override
defaults only for that mutex.</p>
<p>The <directive>Mutex</directive> directive is typically used in
the following exceptional situations:</p>
<ul>
<li>change the mutex mechanism when the default mechanism selected
by <glossary>APR</glossary> has a functional or performance
problem</li>
<li>change the directory used by file-based mutexes when the
default directory does not support locking</li>
</ul>
<note><title>Supported modules</title>
<p>This directive only configures mutexes which have been registered
with the core server using the <code>ap_mutex_register()</code> API.
All modules bundled with httpd support the <directive>Mutex</directive>
directive, but third-party modules may not. Consult the documentation
of the third-party module, which must indicate the mutex name(s) which
can be configured if this directive is supported.</p>
</note>
<p>The following mutex <em>mechanisms</em> are available:</p>
<ul>
<li><code>default | yes</code>
<p>This selects the default locking implementation, as determined by
<glossary>APR</glossary>. The default locking implementation can
be displayed by running <program>httpd</program> with the
<code>-V</code> option.</p></li>
<li><code>none | no</code>
<p>This effectively disables the mutex, and is only allowed for a
mutex if the module indicates that it is a valid choice. Consult the
module documentation for more information.</p></li>
<li><code>posixsem</code>
<p>This is a mutex variant based on a Posix semaphore.</p>
<note type="warning"><title>Warning</title>
<p>The semaphore ownership is not recovered if a thread in the process
holding the mutex segfaults, resulting in a hang of the web server.</p>
</note>
</li>
<li><code>sysvsem</code>
<p>This is a mutex variant based on a SystemV IPC semaphore.</p>
<note type="warning"><title>Warning</title>
<p>It is possible to "leak" SysV semaphores if processes crash
before the semaphore is removed.</p>
</note>
<note type="warning"><title>Security</title>
<p>The semaphore API allows for a denial of service attack by any
CGIs running under the same uid as the webserver (<em>i.e.</em>,
all CGIs, unless you use something like <program>suexec</program>
or <code>cgiwrapper</code>).</p>
</note>
</li>
<li><code>sem</code>
<p>This selects the "best" available semaphore implementation, choosing
between Posix and SystemV IPC semaphores, in that order.</p></li>
<li><code>pthread</code>
<p>This is a mutex variant based on cross-process Posix thread
mutexes.</p>
<note type="warning"><title>Warning</title>
<p>On most systems, if a child process terminates abnormally while
holding a mutex that uses this implementation, the server will deadlock
and stop responding to requests. When this occurs, the server will
require a manual restart to recover.</p>
<p>Solaris is a notable exception as it provides a mechanism which
usually allows the mutex to be recovered after a child process
terminates abnormally while holding a mutex.</p>
<p>If your system implements the
<code>pthread_mutexattr_setrobust_np()</code> function, you may be able
to use the <code>pthread</code> option safely.</p>
</note>
</li>
<li><code>fcntl:/path/to/mutex</code>
<p>This is a mutex variant where a physical (lock-)file and the
<code>fcntl()</code> function are used as the mutex.</p>
<note type="warning"><title>Warning</title>
<p>When multiple mutexes based on this mechanism are used within
multi-threaded, multi-process environments, deadlock errors (EDEADLK)
can be reported for valid mutex operations if <code>fcntl()</code>
is not thread-aware, such as on Solaris.</p>
</note>
</li>
<li><code>flock:/path/to/mutex</code>
<p>This is similar to the <code>fcntl:/path/to/mutex</code> method
with the exception that the <code>flock()</code> function is used to
provide file locking.</p></li>
<li><code>file:/path/to/mutex</code>
<p>This selects the "best" available file locking implementation,
choosing between <code>fcntl</code> and <code>flock</code>, in that
order.</p></li>
</ul>
<p>Most mechanisms are only available on selected platforms, where the
underlying platform and <glossary>APR</glossary> support it. Mechanisms
which aren't available on all platforms are <em>posixsem</em>,
<em>sysvsem</em>, <em>sem</em>, <em>pthread</em>, <em>fcntl</em>,
<em>flock</em>, and <em>file</em>.</p>
<p>With the file-based mechanisms <em>fcntl</em> and <em>flock</em>,
the path, if provided, is a directory where the lock file will be created.
The default directory is httpd's run-time file directory relative to
<directive module="core">ServerRoot</directive>. Always use a local disk
filesystem for <code>/path/to/mutex</code> and never a directory residing
on a NFS- or AFS-filesystem. The basename of the file will be the mutex
type, an optional instance string provided by the module, and unless the
<code>OmitPID</code> keyword is specified, the process id of the httpd
parent process will be appended to to make the file name unique, avoiding
conflicts when multiple httpd instances share a lock file directory. For
example, if the mutex name is <code>mpm-accept</code> and the lock file
directory is <code>/var/httpd/locks</code>, the lock file name for the
httpd instance with parent process id 12345 would be
<code>/var/httpd/locks/mpm-accept.12345</code>.</p>
<note type="warning"><title>Security</title>
<p>It is best to <em>avoid</em> putting mutex files in a world-writable
directory such as <code>/var/tmp</code> because someone could create
a denial of service attack and prevent the server from starting by
creating a lockfile with the same name as the one the server will try
to create.</p>
</note>
<p>The following table documents the names of mutexes used by httpd
and bundled modules.</p>
<table border="1" style="zebra">
<tr>
<th>Mutex name</th>
<th>Module(s)</th>
<th>Protected resource</th>
</tr>
<tr>
<td><code>mpm-accept</code></td>
<td><module>prefork</module> and <module>worker</module> MPMs</td>
<td>incoming connections, to avoid the thundering herd problem;
for more information, refer to the
<a href="../misc/perf-tuning.html">performance tuning</a>
documentation</td>
</tr>
<tr>
<td><code>authdigest-client</code></td>
<td><module>mod_auth_digest</module></td>
<td>client list in shared memory</td>
</tr>
<tr>
<td><code>authdigest-opaque</code></td>
<td><module>mod_auth_digest</module></td>
<td>counter in shared memory</td>
</tr>
<tr>
<td><code>ldap-cache</code></td>
<td><module>mod_ldap</module></td>
<td>LDAP result cache</td>
</tr>
<tr>
<td><code>rewrite-map</code></td>
<td><module>mod_rewrite</module></td>
<td>communication with external mapping programs, to avoid
intermixed I/O from multiple requests</td>
</tr>
<tr>
<td><code>ssl-cache</code></td>
<td><module>mod_ssl</module></td>
<td>SSL session cache</td>
</tr>
<tr>
<td><code>ssl-stapling</code></td>
<td><module>mod_ssl</module></td>
<td>OCSP stapling response cache</td>
</tr>
<tr>
<td><code>watchdog-callback</code></td>
<td><module>mod_watchdog</module></td>
<td>callback function of a particular client module</td>
</tr>
</table>
<p>The <code>OmitPID</code> keyword suppresses the addition of the httpd
parent process id from the lock file name.</p>
<p>In the following example, the mutex mechanism for the MPM accept
mutex will be changed from the compiled-in default to <code>fcntl</code>,
with the associated lock file created in directory
<code>/var/httpd/locks</code>. The mutex mechanism for all other mutexes
will be changed from the compiled-in default to <code>sysvsem</code>.</p>
<example>
Mutex default sysvsem<br />
Mutex mpm-accept fcntl:/var/httpd/locks
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>NameVirtualHost</name>
<description>Designates an IP address for name-virtual
hosting</description>
<syntax>NameVirtualHost <var>addr</var>[:<var>port</var>]</syntax>
<contextlist><context>server config</context></contextlist>
<usage>
<p>A single <directive>NameVirtualHost</directive> 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 <directive>NameVirtualHost</directive>
directive is a required directive if you want to configure
<a href="../vhosts/">name-based virtual hosts</a>.</p>
<p>This directive, and the corresponding <directive >VirtualHost</directive>,
<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>
<example>
NameVirtualHost 192.0.2.1:80<br />
NameVirtualHost *:80<br /><br />
&lt;VirtualHost 192.0.2.1:80&gt;<br />
&nbsp; ServerName namebased-a.example.com<br />
&lt;/VirtualHost&gt;<br />
<br />
&lt;VirtualHost 192.0.2.1:80&gt;<br />
&nbsp; Servername namebased-b.example.com<br />
&lt;/VirtualHost&gt;<br />
<br />
&lt;VirtualHost *:80&gt;<br />
&nbsp; ServerName namebased-c.example.com <br />
&lt;/VirtualHost&gt;<br />
<br />
&lt;VirtualHost *:80&gt;<br />
&nbsp; ServerName namebased-d.example.com <br />
&lt;/VirtualHost&gt;<br />
<br />
</example>
<p>If no matching virtual host is found, then the first listed
virtual host that matches the IP address and port will be used.</p>
<p>IPv6 addresses must be enclosed in square brackets, as shown
in the following example:</p>
<example>
NameVirtualHost [2001:db8::a00:20ff:fea7:ccea]:8080
</example>
<note><title>Argument to <directive type="section">VirtualHost</directive>
directive</title>
<p>Note that the argument to the <directive
type="section">VirtualHost</directive> directive must
exactly match the argument to the <directive
>NameVirtualHost</directive> directive.</p>
<example>
NameVirtualHost 192.0.2.2:80<br />
&lt;VirtualHost 192.0.2.2:80&gt;<br />
# ...<br />
&lt;/VirtualHost&gt;<br />
</example>
</note>
</usage>
<seealso><a href="../vhosts/">Virtual Hosts
documentation</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>Options</name>
<description>Configures what features are available in a particular
directory</description>
<syntax>Options
[+|-]<var>option</var> [[+|-]<var>option</var>] ...</syntax>
<default>Options All</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>Options</override>
<usage>
<p>The <directive>Options</directive> 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>
Execution of CGI scripts using <module>mod_cgi</module>
is permitted.</dd>
<dt><code>FollowSymLinks</code></dt>
<dd>
The server will follow symbolic links in this directory.
<note>
<p>Even though the server follows the symlink it does <em>not</em>
change the pathname used to match against <directive type="section"
module="core">Directory</directive> sections.</p>
<p>Note also, that this option <strong>gets ignored</strong> if set
inside a <directive type="section" module="core">Location</directive>
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>
</note></dd>
<dt><code>Includes</code></dt>
<dd>
Server-side includes provided by <module>mod_include</module>
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
<directive module="mod_alias">ScriptAlias</directive>ed
directories.</dd>
<dt><code>Indexes</code></dt>
<dd>
If a URL which maps to a directory is requested, and there
is no <directive module="mod_dir">DirectoryIndex</directive>
(<em>e.g.</em>, <code>index.html</code>) in that directory, then
<module>mod_autoindex</module> will return a formatted listing
of the directory.</dd>
<dt><code>MultiViews</code></dt>
<dd>
<a href="../content-negotiation.html">Content negotiated</a>
"MultiViews" are allowed using
<module>mod_negotiation</module>.
<note><title>Note</title> <p>This option gets ignored if set
anywhere other than <directive module="core" type="section"
>Directory</directive>, as <module>mod_negotiation</module>
needs real resources to compare against and evaluate from.</p></note>
</dd>
<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.
<note><title>Note</title> <p>This option gets ignored if
set inside a <directive module="core"
type="section">Location</directive> 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></note>
</dd>
</dl>
<p>Normally, if multiple <directive>Options</directive> 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
<directive>Options</directive> 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>
<note type="warning"><title>Warning</title>
<p>Mixing <directive>Options</directive> with a <code>+</code> or
<code>-</code> with those without is not valid syntax, and is likely
to cause unexpected results.</p>
</note>
<p>For example, without any <code>+</code> and <code>-</code> symbols:</p>
<example>
&lt;Directory /web/docs&gt;<br />
<indent>
Options Indexes FollowSymLinks<br />
</indent>
&lt;/Directory&gt;<br />
<br />
&lt;Directory /web/docs/spec&gt;<br />
<indent>
Options Includes<br />
</indent>
&lt;/Directory&gt;
</example>
<p>then only <code>Includes</code> will be set for the
<code>/web/docs/spec</code> directory. However if the second
<directive>Options</directive> directive uses the <code>+</code> and
<code>-</code> symbols:</p>
<example>
&lt;Directory /web/docs&gt;<br />
<indent>
Options Indexes FollowSymLinks<br />
</indent>
&lt;/Directory&gt;<br />
<br />
&lt;Directory /web/docs/spec&gt;<br />
<indent>
Options +Includes -Indexes<br />
</indent>
&lt;/Directory&gt;
</example>
<p>then the options <code>FollowSymLinks</code> and
<code>Includes</code> are set for the <code>/web/docs/spec</code>
directory.</p>
<note><title>Note</title>
<p>Using <code>-IncludesNOEXEC</code> or
<code>-Includes</code> disables server-side includes completely
regardless of the previous setting.</p>
</note>
<p>The default in the absence of any other settings is
<code>All</code>.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>Protocol</name>
<description>Protocol for a listening socket</description>
<syntax>Protocol <var>protocol</var></syntax>
<contextlist><context>server config</context><context>virtual host</context></contextlist>
<compatibility>Available in Apache 2.1.5 and later.
On Windows from Apache 2.3.3 and later.</compatibility>
<usage>
<p>This directive specifies the protocol used for a specific listening socket.
The protocol is used to determine which module should handle a request, and
to apply protocol specific optimizations with the <directive>AcceptFilter</directive>
directive.</p>
<p>You only need to set the protocol if you are running on non-standard ports, otherwise <code>http</code> is assumed for port 80 and <code>https</code> for port 443.</p>
<p>For example, if you are running <code>https</code> on a non-standard port, specify the protocol explicitly:</p>
<example>
Protocol https
</example>
<p>You can also specify the protocol using the <directive module="mpm_common">Listen</directive> directive.</p>
</usage>
<seealso><directive>AcceptFilter</directive></seealso>
<seealso><directive module="mpm_common">Listen</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>RLimitCPU</name>
<description>Limits the CPU consumption of processes launched
by Apache httpd children</description>
<syntax>RLimitCPU <var>seconds</var>|max [<var>seconds</var>|max]</syntax>
<default>Unset; uses operating system defaults</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>All</override>
<usage>
<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 httpd children
servicing requests, not the Apache httpd children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache httpd parent such as piped
logs.</p>
<p>CPU resource limits are expressed in seconds per
process.</p>
</usage>
<seealso><directive module="core">RLimitMEM</directive></seealso>
<seealso><directive module="core">RLimitNPROC</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>RLimitMEM</name>
<description>Limits the memory consumption of processes launched
by Apache httpd children</description>
<syntax>RLimitMEM <var>bytes</var>|max [<var>bytes</var>|max]</syntax>
<default>Unset; uses operating system defaults</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>All</override>
<usage>
<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 httpd children
servicing requests, not the Apache httpd children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache httpd parent such as piped
logs.</p>
<p>Memory resource limits are expressed in bytes per
process.</p>
</usage>
<seealso><directive module="core">RLimitCPU</directive></seealso>
<seealso><directive module="core">RLimitNPROC</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>RLimitNPROC</name>
<description>Limits the number of processes that can be launched by
processes launched by Apache httpd children</description>
<syntax>RLimitNPROC <var>number</var>|max [<var>number</var>|max]</syntax>
<default>Unset; uses operating system defaults</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>All</override>
<usage>
<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 httpd children
servicing requests, not the Apache httpd children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache httpd parent such as piped
logs.</p>
<p>Process limits control the number of processes per user.</p>
<note><title>Note</title>
<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>
</note>
</usage>
<seealso><directive module="core">RLimitMEM</directive></seealso>
<seealso><directive module="core">RLimitCPU</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ScriptInterpreterSource</name>
<description>Technique for locating the interpreter for CGI
scripts</description>
<syntax>ScriptInterpreterSource Registry|Registry-Strict|Script</syntax>
<default>ScriptInterpreterSource Script</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>FileInfo</override>
<compatibility>Win32 only;
option <code>Registry-Strict</code> is available in Apache HTTP Server 2.0 and
later</compatibility>
<usage>
<p>This directive is used to control how Apache httpd finds the
interpreter used to run CGI scripts. The default setting is
<code>Script</code>. This causes Apache httpd 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>
<example>
#!C:/Perl/bin/perl.exe
</example>
<p>or, if <code>perl</code> is in the <code>PATH</code>, simply:</p>
<example>
#!perl
</example>
<p>Setting <code>ScriptInterpreterSource Registry</code> will
cause the Windows Registry tree <code>HKEY_CLASSES_ROOT</code> to be
searched using the script file extension (e.g., <code>.pl</code>) as a
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 httpd falls back to the behavior of the
<code>Script</code> option.</p>
<note type="warning"><title>Security</title>
<p>Be careful when using <code>ScriptInterpreterSource
Registry</code> with <directive
module="mod_alias">ScriptAlias</directive>'ed directories, because
Apache httpd 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>
</note>
<p>The option <code>Registry-Strict</code> which is new in Apache HTTP Server
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>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>SeeRequestTail</name>
<description>Determine if mod_status displays the first 63 characters
of a request or the last 63, assuming the request itself is greater than
63 chars.</description>
<syntax>SeeRequestTail On|Off</syntax>
<default>SeeRequestTail Off</default>
<contextlist><context>server config</context></contextlist>
<compatibility>Available in Apache httpd 2.2.7 and later.</compatibility>
<usage>
<p>mod_status with <code>ExtendedStatus On</code>
displays the actual request being handled.
For historical purposes, only 63 characters of the request
are actually stored for display purposes. This directive
controls whether the 1st 63 characters are stored (the previous
behavior and the default) or if the last 63 characters are. This
is only applicable, of course, if the length of the request is
64 characters or greater.</p>
<p>If Apache httpd is handling <code
>GET&nbsp;/disk1/storage/apache/htdocs/images/imagestore1/food/apples.jpg&nbsp;HTTP/1.1</code
> mod_status displays as follows:
</p>
<table border="1">
<tr>
<th>Off (default)</th>
<td>GET&nbsp;/disk1/storage/apache/htdocs/images/imagestore1/food/apples</td>
</tr>
<tr>
<th>On</th>
<td>orage/apache/htdocs/images/imagestore1/food/apples.jpg&nbsp;HTTP/1.1</td>
</tr>
</table>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ServerAdmin</name>
<description>Email address that the server includes in error
messages sent to the client</description>
<syntax>ServerAdmin <var>email-address</var>|<var>URL</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ServerAdmin</directive> 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>
<p>It may be worth setting up a dedicated address for this, e.g.</p>
<example>
ServerAdmin www-admin@foo.example.com
</example>
<p>as users do not always mention that they are talking about the
server!</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ServerAlias</name>
<description>Alternate names for a host used when matching requests
to name-virtual hosts</description>
<syntax>ServerAlias <var>hostname</var> [<var>hostname</var>] ...</syntax>
<contextlist><context>virtual host</context></contextlist>
<usage>
<p>The <directive>ServerAlias</directive> directive sets the
alternate names for a host, for use with <a
href="../vhosts/name-based.html">name-based virtual hosts</a>. The
<directive>ServerAlias</directive> may include wildcards, if appropriate.</p>
<example>
&lt;VirtualHost *:80&gt;<br />
ServerName server.domain.com<br />
ServerAlias server server2.domain.com server2<br />
ServerAlias *.example.com<br />
UseCanonicalName Off<br />
# ...<br />
&lt;/VirtualHost&gt;
</example>
</usage>
<seealso><directive module="core">UseCanonicalName</directive></seealso>
<seealso><a href="../vhosts/">Apache HTTP Server Virtual Host documentation</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ServerName</name>
<description>Hostname and port that the server uses to identify
itself</description>
<syntax>ServerName [<var>scheme</var>://]<var>fully-qualified-domain-name</var>[:<var>port</var>]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ServerName</directive> directive sets the
request scheme, hostname and
port that the server uses to identify itself. This is used when
creating redirection URLs.</p>
<p>Additionally, <directive>ServerName</directive> is used (possibly
in conjunction with <directive>ServerAlias</directive>) to uniquely
identify a virtual host, when using <a
href="../vhosts/name-based.html">name-based virtual hosts</a>.</p>
<p>For example, if the name of the
machine hosting the web server is <code>simple.example.com</code>,
but the machine also has the DNS alias <code>www.example.com</code>
and you wish the web server to be so identified, the following
directive should be used:</p>
<example>
ServerName www.example.com:80
</example>
<p>The <directive>ServerName</directive> directive
may appear anywhere within the definition of a server. However,
each appearance overrides the previous appearance (within that
server).</p>
<p>If no <directive>ServerName</directive> 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
<directive>ServerName</directive>, 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 <directive>ServerName</directive> directive.</p>
<p>If you are using <a
href="../vhosts/name-based.html">name-based virtual hosts</a>,
the <directive>ServerName</directive> inside a
<directive type="section" module="core">VirtualHost</directive>
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 <directive>ServerName</directive> directive
to make sure that the server generates the correct
self-referential URLs.
</p>
<p>See the description of the
<directive module="core">UseCanonicalName</directive> and
<directive module="core">UseCanonicalPhysicalPort</directive> directives for
settings which determine whether self-referential URLs (e.g., by the
<module>mod_dir</module> module) will refer to the
specified port, or to the port number given in the client's request.
</p>
<note type="warning">
<p>Failure to set <directive>ServerName</directive> to a name that
your server can resolve to an IP address will result in a startup
warning. <code>httpd</code> will then use whatever hostname it can
determine, using the system's <code>hostname</code> command. This
will almost never be the hostname you actually want.</p>
<example>
httpd: Could not reliably determine the server's fully qualified domain name, using rocinante.local for ServerName
</example>
</note>
</usage>
<seealso><a href="../dns-caveats.html">Issues Regarding DNS and
Apache HTTP Server</a></seealso>
<seealso><a href="../vhosts/">Apache HTTP Server virtual host
documentation</a></seealso>
<seealso><directive module="core">UseCanonicalName</directive></seealso>
<seealso><directive module="core">UseCanonicalPhysicalPort</directive></seealso>
<seealso><directive module="core">NameVirtualHost</directive></seealso>
<seealso><directive module="core">ServerAlias</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ServerPath</name>
<description>Legacy URL pathname for a name-based virtual host that
is accessed by an incompatible browser</description>
<syntax>ServerPath <var>URL-path</var></syntax>
<contextlist><context>virtual host</context></contextlist>
<usage>
<p>The <directive>ServerPath</directive> directive sets the legacy
URL pathname for a host, for use with <a
href="../vhosts/">name-based virtual hosts</a>.</p>
</usage>
<seealso><a href="../vhosts/">Apache HTTP Server Virtual Host documentation</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ServerRoot</name>
<description>Base directory for the server installation</description>
<syntax>ServerRoot <var>directory-path</var></syntax>
<default>ServerRoot /usr/local/apache</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>ServerRoot</directive> 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 <directive
module="core">Include</directive> or <directive
module="mod_so">LoadModule</directive>, for example) are taken as
relative to this directory.</p>
<example><title>Example</title>
ServerRoot /home/httpd
</example>
</usage>
<seealso><a href="../invoking.html">the <code>-d</code>
option to <code>httpd</code></a></seealso>
<seealso><a href="../misc/security_tips.html#serverroot">the
security tips</a> for information on how to properly set
permissions on the <directive>ServerRoot</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ServerSignature</name>
<description>Configures the footer on server-generated documents</description>
<syntax>ServerSignature On|Off|EMail</syntax>
<default>ServerSignature Off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <directive>ServerSignature</directive> directive allows the
configuration of a trailing footer line under server-generated
documents (error messages, <module>mod_proxy</module> ftp directory
listings, <module>mod_info</module> 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 <directive
module="core">ServerName</directive> of the serving virtual host,
and the <code>EMail</code> setting additionally creates a
"mailto:" reference to the <directive
module="core">ServerAdmin</directive> of the referenced
document.</p>
<p>After version 2.0.44, the details of the server version number
presented are controlled by the <directive
module="core">ServerTokens</directive> directive.</p>
</usage>
<seealso><directive module="core">ServerTokens</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ServerTokens</name>
<description>Configures the <code>Server</code> HTTP response
header</description>
<syntax>ServerTokens Major|Minor|Min[imal]|Prod[uctOnly]|OS|Full</syntax>
<default>ServerTokens Full</default>
<contextlist><context>server config</context></contextlist>
<usage>
<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>
<dd>Server sends (<em>e.g.</em>): <code>Server: Apache/2.4.1
(Unix) PHP/4.2.2 MyMod/1.2</code></dd>
<dt><code>ServerTokens Prod[uctOnly]</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server:
Apache</code></dd>
<dt><code>ServerTokens Major</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server:
Apache/2</code></dd>
<dt><code>ServerTokens Minor</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server:
Apache/2.4</code></dd>
<dt><code>ServerTokens Min[imal]</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server:
Apache/2.4.1</code></dd>
<dt><code>ServerTokens OS</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server: Apache/2.4.1
(Unix)</code></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 <directive
module="core">ServerSignature</directive> directive.</p>
<note>Setting <directive>ServerTokens</directive> 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.</note>
</usage>
<seealso><directive module="core">ServerSignature</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>SetHandler</name>
<description>Forces all matching files to be processed by a
handler</description>
<syntax>SetHandler <var>handler-name</var>|None</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<compatibility>Moved into the core in Apache httpd 2.0</compatibility>
<usage>
<p>When placed into an <code>.htaccess</code> file or a
<directive type="section" module="core">Directory</directive> or
<directive type="section" module="core">Location</directive>
section, this directive forces all matching files to be parsed
through the <a href="../handler.html">handler</a> given by
<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>
<example>
SetHandler imap-file
</example>
<p>Another example: if you wanted to have the server display a
status report whenever a URL of
<code>http://servername/status</code> was called, you might put
the following into <code>httpd.conf</code>:</p>
<example>
&lt;Location /status&gt;<br />
<indent>
SetHandler server-status<br />
</indent>
&lt;/Location&gt;
</example>
<p>You can override an earlier defined <directive>SetHandler</directive>
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>
</usage>
<seealso><directive module="mod_mime">AddHandler</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>SetInputFilter</name>
<description>Sets the filters that will process client requests and POST
input</description>
<syntax>SetInputFilter <var>filter</var>[;<var>filter</var>...]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<usage>
<p>The <directive>SetInputFilter</directive> 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 module="mod_mime">AddInputFilter</directive>
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>
</usage>
<seealso><a href="../filter.html">Filters</a> documentation</seealso>
</directivesynopsis>
<directivesynopsis>
<name>SetOutputFilter</name>
<description>Sets the filters that will process responses from the
server</description>
<syntax>SetOutputFilter <var>filter</var>[;<var>filter</var>...]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<usage>
<p>The <directive>SetOutputFilter</directive> 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 module="mod_mime">AddOutputFilter</directive>
directive.</p>
<p>For example, the following configuration will process all files
in the <code>/www/data/</code> directory for server-side
includes.</p>
<example>
&lt;Directory /www/data/&gt;<br />
<indent>
SetOutputFilter INCLUDES<br />
</indent>
&lt;/Directory&gt;
</example>
<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>
</usage>
<seealso><a href="../filter.html">Filters</a> documentation</seealso>
</directivesynopsis>
<directivesynopsis>
<name>TimeOut</name>
<description>Amount of time the server will wait for
certain events before failing a request</description>
<syntax>TimeOut <var>seconds</var></syntax>
<default>TimeOut 60</default>
<contextlist><context>server config</context><context>virtual host</context></contextlist>
<usage>
<p>The <directive>TimeOut</directive> directive defines the length
of time Apache httpd 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 <module>mod_cgi</module>, the length of time to wait for
output from a CGI script.</li>
<li>In <module>mod_ext_filter</module>, the length of time to
wait for output from a filtering process.</li>
<li>In <module>mod_proxy</module>, the default timeout value if
<directive module="mod_proxy">ProxyTimeout</directive> is not
configured.</li>
</ol>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>TraceEnable</name>
<description>Determines the behaviour on <code>TRACE</code> requests</description>
<syntax>TraceEnable <var>[on|off|extended]</var></syntax>
<default>TraceEnable on</default>
<contextlist><context>server config</context></contextlist>
<compatibility>Available in Apache HTTP Server 1.3.34, 2.0.55 and later</compatibility>
<usage>
<p>This directive overrides the behavior of <code>TRACE</code> for both
the core server and <module>mod_proxy</module>. 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
<module>mod_proxy</module> 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>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>UnDefine</name>
<description>Undefine the existence of a variable</description>
<syntax>UnDefine <var>parameter-name</var></syntax>
<contextlist><context>server config</context></contextlist>
<usage>
<p>Undoes the effect of a <directive module="core">Define</directive> or
of passing a <code>-D</code> argument to <program>httpd</program>.</p>
<p>This directive can be used to toggle the use of <directive module="core"
type="section">IfDefine</directive> sections without needing to alter
<code>-D</code> arguments in any startup scripts.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>UseCanonicalName</name>
<description>Configures how the server determines its own name and
port</description>
<syntax>UseCanonicalName On|Off|DNS</syntax>
<default>UseCanonicalName Off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context></contextlist>
<usage>
<p>In many situations Apache httpd 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 httpd will use the hostname and port
specified in the <directive module="core">ServerName</directive>
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 httpd 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
that are used to implement <a
href="../vhosts/name-based.html">name-based virtual hosts</a>,
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
<code>http://www/splat</code>, <em>without the trailing
slash</em> then Apache httpd will redirect them to
<code>http://www.domain.com/splat/</code>. If you have
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
<directive>UseCanonicalName</directive> is set <code>Off</code>, then
Apache httpd will redirect to <code>http://www/splat/</code>.</p>
<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 httpd does a
reverse DNS lookup on the server IP address that the client
connected to in order to work out self-referential URLs.</p>
<note type="warning"><title>Warning</title>
<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>
</note>
</usage>
<seealso><directive module="core">UseCanonicalPhysicalPort</directive></seealso>
<seealso><directive module="core">ServerName</directive></seealso>
<seealso><directive module="mpm_common">Listen</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>UseCanonicalPhysicalPort</name>
<description>Configures how the server determines its own name and
port</description>
<syntax>UseCanonicalPhysicalPort On|Off</syntax>
<default>UseCanonicalPhysicalPort Off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context></contextlist>
<usage>
<p>In many situations Apache httpd 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 httpd will, when
constructing the canonical port for the server to honor
the <directive module="core">UseCanonicalName</directive> directive,
provide the actual physical port number being used by this request
as a potential port. With <code>UseCanonicalPhysicalPort Off</code>
Apache httpd will not ever use the actual physical port number, instead
relying on all configured information to construct a valid port number.</p>
<note><title>Note</title>
<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>
</note>
</usage>
<seealso><directive module="core">UseCanonicalName</directive></seealso>
<seealso><directive module="core">ServerName</directive></seealso>
<seealso><directive module="mpm_common">Listen</directive></seealso>
</directivesynopsis>
<directivesynopsis type="section">
<name>VirtualHost</name>
<description>Contains directives that apply only to a specific
hostname or IP address</description>
<syntax>&lt;VirtualHost
<var>addr</var>[:<var>port</var>] [<var>addr</var>[:<var>port</var>]]
...&gt; ... &lt;/VirtualHost&gt;</syntax>
<contextlist><context>server config</context></contextlist>
<usage>
<p><directive type="section">VirtualHost</directive> and
<code>&lt;/VirtualHost&gt;</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 <directive type="section">VirtualHost</directive>
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>
<example><title>Example</title>
&lt;VirtualHost 10.1.2.3&gt;<br />
<indent>
ServerAdmin webmaster@host.example.com<br />
DocumentRoot /www/docs/host.example.com<br />
ServerName host.example.com<br />
ErrorLog logs/host.example.com-error_log<br />
TransferLog logs/host.example.com-access_log<br />
</indent>
&lt;/VirtualHost&gt;
</example>
<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>
<example>
&lt;VirtualHost [2001:db8::a00:20ff:fea7:ccea]&gt;<br />
<indent>
ServerAdmin webmaster@host.example.com<br />
DocumentRoot /www/docs/host.example.com<br />
ServerName host.example.com<br />
ErrorLog logs/host.example.com-error_log<br />
TransferLog logs/host.example.com-access_log<br />
</indent>
&lt;/VirtualHost&gt;
</example>
<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>
<note><title>Note</title>
<p>The use of <directive type="section">VirtualHost</directive> does
<strong>not</strong> affect what addresses Apache httpd listens on. You
may need to ensure that Apache httpd is listening on the correct addresses
using <directive module="mpm_common">Listen</directive>.</p>
</note>
<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
most recent <directive module="mpm_common">Listen</directive>
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 <directive module="core">ServerName</directive> should be
specified inside each <directive
type="section">VirtualHost</directive> block. If it is absent, the
<directive module="core">ServerName</directive> from the "main"
server configuration will be inherited.</p>
<p>If no matching virtual host is found, then the first listed
virtual host that matches the IP address will be used. As a
consequence, the first listed virtual host is the default virtual
host.</p>
<note type="warning"><title>Security</title>
<p>See the <a href="../misc/security_tips.html">security tips</a>
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>
</note>
</usage>
<seealso><a href="../vhosts/">Apache HTTP Server Virtual Host documentation</a></seealso>
<seealso><a href="../dns-caveats.html">Issues Regarding DNS and
Apache HTTP Server</a></seealso>
<seealso><a href="../bind.html">Setting
which addresses and ports Apache HTTP Server uses</a></seealso>
<seealso><a href="../sections.html">How &lt;Directory&gt;, &lt;Location&gt;
and &lt;Files&gt; sections work</a> for an explanation of how these
different sections are combined when a request is received</seealso>
</directivesynopsis>
</modulesynopsis>