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<?xml version="1.0"?>
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<modulesynopsis metafile="core.xml.meta">
<name>core</name>
<description>Core Apache HTTP Server features that are always
available</description>
<status>Core</status>
<directivesynopsis>
<name>AcceptFilter</name>
<description>Configures optimizations for a Protocol's Listener Sockets</description>
<syntax>AcceptFilter <var>protocol</var> <var>accept_filter</var></syntax>
<contextlist><context>server config</context></contextlist>
<compatibility>Available in Apache 2.1.5 and later</compatibility>
<usage>
<p>This directive enables operating system specific optimizations for a
listening socket by the Protocol type. The basic premise is for the
kernel to not send a socket to the server process until either data
is received or an entire HTTP Request is buffered. Only
FreeBSD's Accept Filters</a> and Linux's more primitive
<code>TCP_DEFER_ACCEPT</code> are currently supported.</p>
<p>The default values on FreeBSD are:</p>
<example>
AcceptFilter http httpready <br/>
AcceptFilter https dataready
</example>
<p>The <code>httpready</code> accept filter buffers entire HTTP requests at
the kernel level. Once an entire request is recieved, the kernel then
sends it to the server. See the
accf_http(9)</a> man page for more details. Since HTTPS requests are
encrypted only the <a href="http://www.freebsd.org/cgi/man.cgi?query=accf_data&sektion=9">
accf_data(9)</a> filter is used.</p>
<p>The default values on Linux are:</p>
<example>
AcceptFilter http data <br/>
AcceptFilter https data
</example>
<p>Linux's <code>TCP_DEFER_ACCEPT</code> does not support buffering http
requests. Any value besides <code>none</code> will enable
<code>TCP_DEFER_ACCEPT</code> on that listener. For more details
see the Linux
tcp(7)</a> man page.</p>
<p>Using <code>none</code> for an argument will disable any accept filters
for that protocol. This is useful for protocols that require a server
send data first, such as <code>nntp</code>:</p>
<example>AcceptFilter nntp none</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AcceptPathInfo</name>
<description>Resources accept trailing pathname information</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>Available in Apache 2.0.30 and later</compatibility>
<usage>
<p>This directive controls whether requests that contain trailing
pathname information that follows an actual filename (or
non-existent file in an existing directory) will be accepted or
rejected. The trailing pathname information can be made
available to scripts in the <code>PATH_INFO</code> environment
variable.</p>
<p>For example, assume the location <code>/test/</code> points to
a directory that contains only the single file
<code>/more</code> as <code>PATH_INFO</code>.</p>
<p>The three possible arguments for the
<directive>AcceptPathInfo</directive> directive are:</p>
<dl>
<dt><code>Off</code></dt><dd>A request will only be accepted if it
maps to a literal path that exists. Therefore a request with
trailing pathname information after the true filename such as
a 404 NOT FOUND error.</dd>
<dt><code>On</code></dt><dd>A request will be accepted if a
leading path component maps to a file that exists. The above
<dt><code>Default</code></dt><dd>The treatment of requests with
trailing pathname information is determined by the <a
href="/handler.html">handler</a> responsible for the request.
The core handler for normal files defaults to rejecting
<code>PATH_INFO</code> requests. Handlers that serve scripts, such as <a
href="mod_isapi.html">isapi-handler</a>, generally accept
<code>PATH_INFO</code> by default.</dd>
</dl>
<p>The primary purpose of the <code>AcceptPathInfo</code>
directive is to allow you to override the handler's choice of
accepting or rejecting <code>PATH_INFO</code>. This override is required,
based on <code>PATH_INFO</code>. The core handler would usually reject
the request, so you can use the following configuration to enable
such a script:</p>
<example>
<Files "mypaths.shtml"><br />
<indent>
Options +Includes<br />
SetOutputFilter INCLUDES<br />
AcceptPathInfo On<br />
</indent>
</Files>
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AccessFileName</name>
<description>Name of the distributed configuration file</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>While processing a request the server looks for
the first existing configuration file from this list of names in
every directory of the path to the document, if distributed
configuration files are <a href="#allowoverride">enabled for that
directory</a>. For example:</p>
<example>
AccessFileName .acl
</example>
<p>before returning the document
for directives, unless they have been disabled with</p>
<example>
<Directory /><br />
<indent>
AllowOverride None<br />
</indent>
</Directory>
</example>
</usage>
<seealso><directive module="core">AllowOverride</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AddDefaultCharset</name>
<description>Default charset parameter to be added when a response
<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
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 MIME media 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>AddOutputFilterByType</name>
<description>assigns an output filter to a particular MIME-type</description>
<syntax>AddOutputFilterByType <var>filter</var>[;<var>filter</var>...]
<var>MIME-type</var> [<var>MIME-type</var>] ...</syntax>
<contextlist><context>server config</context>
<context>virtual host</context><context>directory</context>
<context>.htaccess</context></contextlist>
<override>FileInfo</override>
<compatibility>Available in Apache 2.0.33 and later; deprecated in Apache 2.1 and later</compatibility>
<usage>
<p>This directive activates a particular output <a
href="/filter.html">filter</a> for a request depending on the
response <glossary>MIME-type</glossary>. Because of certain
problems discussed below, this directive is deprecated. The same
functionality is available using <module>mod_filter</module>.</p>
<p>The following example uses the <code>DEFLATE</code> filter, which
is provided by <module>mod_deflate</module>. It will compress all
output (either static or dynamic) which is labeled as
to the client.</p>
<example>
</example>
<p>If you want the content to be processed by more than one filter, their
names have to be separated by semicolons. It's also possible to use one
<directive>AddOutputFilterByType</directive> directive for each of
these filters.</p>
<p>The configuration below causes all script output labeled as
<code>INCLUDES</code> filter and then by the <code>DEFLATE</code>
filter.</p>
<example>
<Location /cgi-bin/><br />
<indent>
Options Includes<br />
</indent>
</Location>
</example>
<note type="warning"><title>Note</title>
<p>Enabling filters with <directive>AddOutputFilterByType</directive>
may fail partially or completely in some cases. For example, no
filters are applied if the <glossary>MIME-type</glossary> could not be determined and falls
back to the <directive module="core">DefaultType</directive> setting,
even if the <directive module="core">DefaultType</directive> is the
same.</p>
<p>However, if you want to make sure, that the filters will be
applied, assign the content type to a resource explicitly, for
example with <directive module="mod_mime">AddType</directive> or
<directive module="core">ForceType</directive>. Setting the
content type within a (non-nph) CGI script is also safe.</p>
<p>The by-type output filters are never applied on proxy requests.</p>
</note>
</usage>
<seealso><directive module="mod_mime">AddOutputFilter</directive></seealso>
<seealso><directive module="core">SetOutputFilter</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 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 All</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 <Directory> 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="core">AuthName</directive>,
<directive module="core">AuthType</directive>, <directive
module="mod_authn_file">AuthUserFile</directive>, <directive
module="core">Require</directive>, <em>etc.</em>).</dd>
<dt>FileInfo</dt>
<dd>
Allow use of the directives controlling document types (<directive
module="core">DefaultType</directive>, <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, <em>etc.</em>), 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>
</usage>
<seealso><directive module="core">AccessFileName</directive></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 finds the
interpreter used to run CGI scripts. For example, setting
cause all CGI script files with a <code>.foo</code> extension to
be passed to the FOO interpreter.</p>
</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 RFC2068.</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>MIME content-type that will be sent if the
server cannot determine a type in any other way</description>
<syntax>DefaultType <var>MIME-type</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<usage>
<p>There will be times when the server is asked to provide a
document whose type cannot be determined by its <glossary
ref="mime-type">MIME types</glossary> mappings.</p>
<p>The server must inform the client of the content-type of the
document, so in the event of an unknown type it uses the
<code>DefaultType</code>. For example:</p>
<example>
</example>
<p>would be appropriate for a directory which contained many GIF
images with filenames missing the <code>.gif</code> extension.</p>
<p>Note that unlike <directive
module="core">ForceType</directive>, this directive only
provides the default mime-type. All other mime-type definitions,
including filename extensions, that might identify the media type
will override this default.</p>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Directory</name>
<description>Enclose a group of directives that apply only to the
named file-system directory and sub-directories</description>
<syntax><Directory <var>directory-path</var>>
... </Directory></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p><directive type="section">Directory</directive> and
<code></Directory></code> are used to enclose a group of
directives that will apply only to the named directory and
sub-directories of that directory. Any directive that is allowed
in a directory context may be used. <var>Directory-path</var> is
either the full path to a directory, or a wild-card string using
Unix shell-style matching. In a wild-card string, <code>?</code> matches
any single character, and <code>*</code> matches any sequences of
characters. You may also use <code>[]</code> character ranges. None
of the wildcards match a `/' character, so <code><Directory
/*/public_html></code> will not match
/home/*/public_html></code> will match. Example:</p>
<example>
<indent>
Options Indexes FollowSymLinks<br />
</indent>
</Directory>
</example>
<note>
<p>Be careful with the <var>directory-path</var> arguments:
They have to literally match the filesystem path which Apache uses
to access the files. Directives applied to a particular
<code><Directory></code> will not apply to files accessed from
that same directory via a different path, such as via different symbolic
links.</p>
</note>
<p><glossary ref="regex">Regular
expressions</glossary> can also be used, with the addition of the
<code>~</code> character. For example:</p>
<example>
<Directory ~ "^/www/.*/[0-9]{3}">
</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>
<Directory /><br />
<indent>
AllowOverride None<br />
</indent>
</Directory><br />
<br />
<Directory /home/><br />
<indent>
AllowOverride FileInfo<br />
</indent>
</Directory>
</example>
the steps are:</p>
<ul>
<li>Apply directive <code>AllowOverride None</code>
(disabling <code>.htaccess</code> files).</li>
<li>Apply directive <code>AllowOverride FileInfo</code> (for
directory <code>/home</code>).</li>
<li>Apply any <code>FileInfo</code> directives in
</ul>
<p>Regular expressions are not considered until after all of the
normal sections have been applied. Then all of the regular
expressions are tested in the order they appeared in the
configuration file. For example, with</p>
<example>
<Directory ~ abc$><br />
<indent>
# ... directives here ...<br />
</indent>
</Directory>
</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
the corresponding <directive type="section">Directory</directive> will
be applied.</p>
<p><strong>Note that the default Apache access for
<code><Directory /></code> is <code>Allow from All</code>.
This means that Apache will serve any file mapped from an URL. It is
recommended that you change this with a block such
as</strong></p>
<example>
<Directory /><br />
<indent>
Order Deny,Allow<br />
Deny from All<br />
</indent>
</Directory>
</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>
<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>
<Location> and <Files> 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
file-system directories matching a regular expression and their
subdirectories</description>
<syntax><DirectoryMatch <var>regex</var>>
... </DirectoryMatch></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p><directive type="section">DirectoryMatch</directive> and
<code></DirectoryMatch></code> are used to enclose a group
of directives which will apply only to the named directory and
sub-directories of that directory, the same as <directive
module="core" type="section">Directory</directive>. However, it
takes as an argument a <glossary ref="regex">regular
expression</glossary>. For example:</p>
<example>
<DirectoryMatch "^/www/(.+/)?[0-9]{3}">
</example>
<p>would match directories in <code>/www/</code> that consisted of three
numbers.</p>
</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 <Directory>, <Location> and
<Files> 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>
<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>
</example>
<p>then an access to
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>
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
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>With an NFS-mounted <directive module="core">DocumentRoot</directive>,
the <program>httpd</program> may crash due to a segmentation fault if a file
is deleted or truncated while the <program>httpd</program> has it
memory-mapped.</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>
<Directory "/path-to-nfs-files">
<indent>
EnableMMAP Off
</indent>
</Directory>
</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 On</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</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 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
the kernel may be unable to serve the network file through
its own cache.</li>
</ul>
<p>For server configurations that are vulnerable to these problems,
you should disable this feature by specifying:</p>
<example>
EnableSendfile Off
</example>
<p>For NFS or SMB mounted files, this feature may be disabled explicitly
for the offending files by specifying:</p>
<example>
<Directory "/path-to-nfs-files">
<indent>
EnableSendfile Off
</indent>
</Directory>
</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>
<compatibility>Quoting syntax for text messages is different in Apache
2.0</compatibility>
<usage>
<p>In the event of a problem or error, Apache can be configured
to do one of four things,</p>
<ol>
<li>output a simple hardcoded error message</li>
<li>output a customized message</li>
<li>redirect to a local <var>URL-path</var> to handle the
<li>redirect to an external <var>URL</var> to handle the
</ol>
<p>The first option is the default, while options 2-4 are
configured using the <directive>ErrorDocument</directive>
directive, which is followed by the HTTP response code and a URL
or a message. Apache will sometimes offer additional information
<p>URLs can begin with a slash (/) for local web-paths (relative
to the <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 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's simple hardcoded message. While not required
under normal circumstances, <code>default</code> will restore
Apache's simple hardcoded message for configurations that would
otherwise inherit an existing <directive>ErrorDocument</directive>.</p>
<example>
<indent>
ErrorDocument 404 default<br />
</indent>
</Directory>
</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 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
>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>Prior to version 2.0, messages were indicated by prefixing
them with a single unmatched double quote character.</p>
</usage>
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>
<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>
</example>
<p>If the <var>file-path</var>
begins with a pipe (|) then it is assumed to be a command to spawn
to handle the error log.</p>
<example><title>Example</title>
</example>
<p>Using <code>syslog</code> instead of a filename enables logging
via syslogd(8) if the system supports it. The default is to use
syslog facility <code>local7</code>, but you can override this by
using the <code>syslog:<var>facility</var></code> syntax where
<var>facility</var> can be one of the names usually documented in
syslog(1).</p>
<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>
</directivesynopsis>
<directivesynopsis>
<name>FileETag</name>
<description>File attributes used to create the ETag
HTTP response header</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 file.
(The <code>ETag</code> value is used in cache management to save
network bandwidth.) In Apache 1.3.22 and earlier, the
<code>ETag</code> value was <em>always</em> formed
from the file's inode, size, and last-modified time (mtime). The
<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 INode MTime Size</code>, and a
subdirectory's includes <code>FileETag -INode</code>,
the setting for that subdirectory (which will be inherited by
any sub-subdirectories that don't override it) will be equivalent to
<code>FileETag MTime Size</code>.</p>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Files</name>
<description>Contains directives that apply to matched
filenames</description>
<syntax><Files <var>filename</var>> ... </Files></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></Files></code>
directive. The directives given within this section will be applied to
any object with a basename (last component of filename) matching the
specified filename. <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>
<Files ~ "\.(gif|jpe?g|png)$">
</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>
and <Files> 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><FilesMatch <var>regex</var>> ... </FilesMatch></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>
<FilesMatch "\.(gif|jpe?g|png)$">
</example>
<p>would match most common Internet graphics formats.</p>
</usage>
and <Files> 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
MIME content-type</description>
<syntax>ForceType <var>MIME-type</var>|None</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<compatibility>Moved to the core in Apache 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>MIME-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>
</example>
<p>Note that unlike <directive module="core">DefaultType</directive>,
this directive overrides all mime-type associations, including
filename extensions, that might identify the media type.</p>
<p>You can override any <directive>ForceType</directive> setting
by using the value of <code>None</code>:</p>
<example>
<Location /images><br />
<indent>
</indent>
</Location><br />
<br />
# but normal mime-type associations here:<br />
<indent>
ForceType None<br />
</indent>
</Location>
</example>
</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
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>IfDefine</name>
<description>Encloses directives that will be processed only
if a test is true at startup</description>
<syntax><IfDefine [!]<var>parameter-name</var>> ...
</IfDefine></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <code><IfDefine <var>test</var>>...</IfDefine>
</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.</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 ...<br />
<br />
# httpd.conf<br />
<IfDefine ReverseProxy><br />
<indent>
</indent>
</IfDefine>
</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><IfModule [!]<var>module-file</var>|<var>module-identifier</var>> ...
</IfModule></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><IfModule <var>test</var>>...</IfModule></code>
section is used to mark directives that are conditional on the presence of
a specific module. The directives within an <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 -- 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
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>file-path</var>|<var>directory-path</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</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 to
include several files at once, in alphabetical order. In
addition, if <directive>Include</directive> points to a directory,
rather than a file, Apache will read all files in that directory
and any subdirectory. But 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.</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>
</example>
<p>Or, providing paths relative to your <directive
module="core">ServerRoot</directive> directory:</p>
<example>
</example>
<p>Running <code>apachectl configtest</code> will give you a list
of the files that are being processed during the configuration
check:</p>
<example>
root@host# apachectl configtest<br />
Syntax OK
</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>
which allow multiple requests to be sent over the same TCP
connection. In some cases this has been shown to result in an
almost 50% speedup in latency times for HTML documents with
many images. To enable Keep-Alive connections, set
<code>KeepAlive On</code>.</p>
used if they are specifically requested by a client. In
only be used when the length of the content is known in
advance. This implies that dynamic content such as CGI output,
SSI pages, and server-generated directory listings will
unless otherwise specified. If the client requests it, chunked
encoding will be used in order to send content of unknown
length over persistent connections.</p>
<p>When a client uses a Keep-Alive connection it will be counted
as a single "request" for the MaxRequestsPerChild 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>seconds</var></syntax>
<default>KeepAliveTimeout 5</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The number of seconds Apache will wait for a subsequent
request before closing the connection. 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>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Limit</name>
<description>Restrict enclosed access controls to only certain HTTP
methods</description>
<syntax><Limit <var>method</var> [<var>method</var>] ... > ...
</Limit></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</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>
<Limit POST PUT DELETE><br />
<indent>
Require valid-user<br />
</indent>
</Limit>
</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.</p>
<note type="warning">A <directive type="section"
module="core">LimitExcept</directive> section should always be
used in preference to a <directive type="section"
module="core">Limit</directive> section when restricting access,
since a <directive type="section"
module="core">LimitExcept</directive> section provides protection
against arbitrary methods.</note>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>LimitExcept</name>
<description>Restrict access controls to all HTTP methods
except the named ones</description>
<syntax><LimitExcept <var>method</var> [<var>method</var>] ... > ...
</LimitExcept></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p><directive type="section">LimitExcept</directive> and
<code></LimitExcept></code> are used to enclose
a group of access control directives which will then apply to any
HTTP access method <strong>not</strong> listed in the arguments;
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>
<LimitExcept POST GET><br />
<indent>
Require valid-user<br />
</indent>
</LimitExcept>
</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 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'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.</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>
</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></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>
</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></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>
</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></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>
</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><Location
<var>URL-path</var>|<var>URL</var>> ... </Location></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></Location></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>
<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><Location /></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>. No scheme, hostname,
port, or query string may be included. For proxy requests, the
URL to be matched is of the form
prefix.</p>
<p>The URL may use wildcards. In a wild-card string, <code>?</code> matches
any single character, and <code>*</code> matches any sequences of
characters.</p>
<p><glossary ref="regex">Regular expressions</glossary>
can also be used, with the addition of the
<code>~</code> character. For example:</p>
<example>
<Location ~ "/(extra|special)/data">
</example>
type="section" module="core">LocationMatch</directive> behaves
identical to the regex version of <directive
type="section">Location</directive>.</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
<example>
<Location /status><br />
<indent>
SetHandler server-status<br />
Order Deny,Allow<br />
Deny from all<br />
Allow from .foo.com<br />
</indent>
</Location>
</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
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><LocationMatch ^/abc></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,
request is to <code>/abc//def</code> then it will match.</p>
</note>
</usage>
and <Files> sections work</a> for an explanation of how these
different sections are combined when a request is received</seealso>
</directivesynopsis>
<directivesynopsis type="section">
<name>LocationMatch</name>
<description>Applies the enclosed directives only to regular-expression
matching URLs</description>
<syntax><LocationMatch
<var>regex</var>> ... </LocationMatch></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>
<LocationMatch "/(extra|special)/data">
</example>
</usage>
and <Files> 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>level</var></syntax>
<default>LogLevel warn</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<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
</tr>
<tr>
<td><code>debug</code> </td>
<td>Debug-level messages</td>
<td>"Opening config file ..."</td>
</tr>
</table>
<p>When a particular level is specified, messages from all
other levels of higher significance will be reported as well.
then messages with log levels of <code>notice</code> and
<code>warn</code> will also be posted.</p>
<p>Using a level of at least <code>crit</code> is
recommended.</p>
<p>For example:</p>
<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>
</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>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>The <directive>NameVirtualHost</directive> directive is a
required directive if you want to configure <a
<p>Although <var>addr</var> can be hostname it is recommended
that you always use an IP address, e.g.</p>
<example>
NameVirtualHost 111.22.33.44
</example>
<p>With the <directive>NameVirtualHost</directive> directive you
specify the IP address on which the server will receive requests
for the name-based virtual hosts. This will usually be the address
to which your name-based virtual host names resolve. 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. If you have multiple name-based hosts on
multiple addresses, repeat the directive for each address.</p>
<note><title>Note</title>
<p>Note, that the "main server" and any <code>_default_</code> servers
will <strong>never</strong> be served for a request to a
<directive>NameVirtualHost</directive> IP address (unless for some
reason you specify <directive>NameVirtualHost</directive> but then
don't define any <directive>VirtualHost</directive>s for that
address).</p>
</note>
<p>Optionally you can specify a port number on which the
name-based virtual hosts should be used, e.g.</p>
<example>
NameVirtualHost 111.22.33.44:8080
</example>
<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>
<p>To receive requests on all interfaces, you can use an argument of
<code>*</code></p>
<example>
NameVirtualHost *
</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 1.2.3.4<br />
<VirtualHost 1.2.3.4><br />
# ...<br />
</VirtualHost><br />
</example>
</note>
</usage>
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>
</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>
<module>mod_autoindex</module> will return a formatted listing
of the directory.</dd>
<dt><code>MultiViews</code></dt>
<dd>
"MultiViews" are allowed using
<module>mod_negotiation</module>.</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> This option gets ignored if
set inside a <directive module="core"
type="section">Location</directive> section.</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>
<indent>
Options Indexes FollowSymLinks<br />
</indent>
</Directory><br />
<br />
<indent>
Options Includes<br />
</indent>
</Directory>
</example>
<p>then only <code>Includes</code> will be set for the
<directive>Options</directive> directive uses the <code>+</code> and
<code>-</code> symbols:</p>
<example>
<indent>
Options Indexes FollowSymLinks<br />
</indent>
</Directory><br />
<br />
<indent>
Options +Includes -Indexes<br />
</indent>
</Directory>
</example>
<p>then the options <code>FollowSymLinks</code> and
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>RLimitCPU</name>
<description>Limits the CPU consumption of processes launched
by Apache 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 children
servicing requests, not the Apache children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache parent such as piped
logs.</p>
<p>CPU resource limits are expressed in seconds per
process.</p>
</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 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 children
servicing requests, not the Apache children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache parent such as piped
logs.</p>
<p>Memory resource limits are expressed in bytes per
process.</p>
</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 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 children
servicing requests, not the Apache children themselves. This
includes CGI scripts and SSI exec commands, but not any
processes forked off from the Apache parent such as piped
logs.</p>
<p>Process limits control the number of processes per user.</p>
<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 2.0 and
later</compatibility>
<usage>
<p>This directive is used to control how Apache finds the
interpreter used to run CGI scripts. The default setting is
<code>Script</code>. This causes Apache to use the interpreter pointed to
by the shebang line (first line, starting with <code>#!</code>) in the
script. On Win32 systems this line usually looks like:</p>
<example>
</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
search key. The command defined by the registry subkey
<code>Shell\ExecCGI\Command</code> or, if it does not exist, by the subkey
<code>Shell\Open\Command</code> is used to open the script file. If the
registry keys cannot be found, Apache falls back to the behavior of the
<code>Script</code> option.</p>
<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 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
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>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>
<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
<example>
<VirtualHost *><br />
ServerName server.domain.com<br />
ServerAlias server server2.domain.com server2<br />
# ...<br />
</VirtualHost>
</example>
</usage>
</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>
<compatibility>In version 2.0, this
directive supersedes the functionality of the <directive>Port</directive>
directive from version 1.3.</compatibility>
<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. For example, if the name of the
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>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>
</usage>
Apache</a></seealso>
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
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ServerRoot</name>
<description>Base directory for the server installation</description>
<syntax>ServerRoot <var>directory-path</var></syntax>
<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>
</example>
</usage>
option to <code>httpd</code></a></seealso>
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 Prod[uctOnly]</code></dt>
Apache</code></dd>
<dt><code>ServerTokens Major</code></dt>
Apache/2</code></dd>
<dt><code>ServerTokens Minor</code></dt>
<dt><code>ServerTokens Min[imal]</code></dt>
<dt><code>ServerTokens OS</code></dt>
(Unix)</code></dd>
<dt><code>ServerTokens Full</code> (or not specified)</dt>
</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>
</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 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
<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
<example>
<Location /status><br />
<indent>
SetHandler server-status<br />
</indent>
</Location>
</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>
</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
includes.</p>
<example>
<indent>
SetOutputFilter INCLUDES<br />
</indent>
</Directory>
</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>
</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 300</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>TimeOut</directive> directive currently defines
the amount of time Apache will wait for three things:</p>
<ol>
<li>The total amount of time it takes to receive a GET
request.</li>
<li>The amount of time between receipt of TCP packets on a
POST or PUT request.</li>
<li>The amount of time between ACKs on transmissions of TCP
packets in responses.</li>
</ol>
<p>We plan on making these separately configurable at some point
down the road. The timer used to default to 1200 before 1.2,
but has been lowered to 300 which is still far more than
necessary in most situations. It is not set any lower by
default because there may still be odd places in the code where
the timer is not reset when a packet is sent. </p>
</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 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>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 must construct a <em>self-referential</em>
URL -- that is, a URL that refers back to the same server. With
<code>UseCanonicalName On</code> Apache will use the hostname and port
specified in the <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 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
slash</em> then Apache will redirect them to
authentication enabled, this will cause the user to have to
authenticate twice (once for <code>www</code> and once again
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
<p>There is a third option, <code>UseCanonicalName DNS</code>,
which is intended for use with mass IP-based virtual hosting to
support ancient clients that do not provide a
<code>Host:</code> header. With this option Apache does a
reverse DNS lookup on the server IP address that the client
connected to in order to work out self-referential URLs.</p>
<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 must construct a <em>self-referential</em>
URL -- that is, a URL that refers back to the same server. With
<code>UseCanonicalPhysicalPort On</code> Apache will, when
constructing the canonical port for the server to honor
the <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 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><VirtualHost
<var>addr</var>[:<var>port</var>] [<var>addr</var>[:<var>port</var>]]
...> ... </VirtualHost></syntax>
<contextlist><context>server config</context></contextlist>
<usage>
<p><directive type="section">VirtualHost</directive> and
<code></VirtualHost></code> are used to enclose a group of
directives that will apply only to a particular virtual host. Any
directive that is allowed in a virtual host context may be
used. When the server receives a request for a document on a
particular virtual host, it uses the configuration directives
enclosed in the <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;</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>
<VirtualHost 10.1.2.3><br />
<indent>
ServerAdmin webmaster@host.foo.com<br />
ServerName host.foo.com<br />
</indent>
</VirtualHost>
</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>
<VirtualHost [2001:db8::a00:20ff:fea7:ccea]><br />
<indent>
ServerAdmin webmaster@host.example.com<br />
ServerName host.example.com<br />
</indent>
</VirtualHost>
</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 listens on. You
may need to ensure that Apache 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. (But note that any IP
address that matches a <directive
module="core">NameVirtualHost</directive> directive will use neither
the "main" server config nor the <code>_default_</code> virtual host.
documentation for further details.)</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>
<note type="warning"><title>Security</title>
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>
Apache</a></seealso>
which addresses and ports Apache uses</a></seealso>
and <Files> sections work</a> for an explanation of how these
different sections are combined when a request is received</seealso>
</directivesynopsis>
</modulesynopsis>