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apache/docs/manual/mod/core.xml
Justin Erenkrantz b8b583d0c4 The value emitted by ServerSignature now mimics the Server HTTP header as 
controlled by ServerTokens.

Submitted by:	Francis Daly <deva@daoine.org>
Reviewed by:	Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97416 13f79535-47bb-0310-9956-ffa450edef68
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<?xml version="1.0"?>
<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
<modulesynopsis>
<name>core</name>
<description>Core Apache HTTP Server features that are always
available</description>
<status>Core</status>
<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 PATH_INFO environment variable.</p>
<p>For example, assume the location <code>/test/</code> points to
a directory that contains only the single file
<code>here.html</code>. Then requests for
<code>/test/here.html/more</code> and
<code>/test/nothere.html/more</code> both collect
<code>/more</code> as PATH_INFO.</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
<code>/test/here.html/more</code> in the above example will return
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
example <code>/test/here.html/more</code> will be accepted if
<code>/test/here.html</code> maps to a valid file.</dd>
<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 PATH_INFO.
Handlers that serve scripts, such as <a
href="mod_cgi.html">cgi-script</a> and <a
href="mod_isapi.html">isapi-isa</a>, generally accept PATH_INFO 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 PATH_INFO. This override is required, for
example, when you use a <a href="../filter.html">filter</a>, such
as <a href="mod_include.html">INCLUDES</a>, to generate content
based on PATH_INFO. The core handler would usually reject the
request, so you can use the following configuration to enable
such a script:</p>
<example>
&lt;Files "mypaths.shtml"&gt;<br />
<indent>
Options +Includes<br />
SetOutputFilter INCLUDES<br />
AcceptPathInfo on<br />
</indent>
&lt;/Files&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AccessFileName</name>
<description>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>When returning a document to the client 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 enabled for that directory. For
example:</p>
<example>
AccessFileName .acl
</example>
<p>before returning the document
<code>/usr/local/web/index.html</code>, the server will read
<code>/.acl</code>, <code>/usr/.acl</code>,
<code>/usr/local/.acl</code> and <code>/usr/local/web/.acl</code>
for directives, unless they have been disabled with</p>
<example>
&lt;Directory /&gt;<br />
<indent>
AllowOverride None<br />
</indent>
&lt;/Directory&gt;
</example>
</usage>
<seealso><directive module="core">AllowOverride</directive></seealso>
<seealso><a href="../configuring.html">Configuration Files</a></seealso>
<seealso><a href="../howto/htaccess.html">.htaccess Files</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AddDefaultCharset</name>
<description>Default character set to be added for a
response without an explicit character set</description>
<syntax>AddDefaultCharset On|Off|<var>charset</var></syntax>
<default>AddDefaultCharset Off</default>
<contextlist><context>server config</context>
<context>virtual host</context><context>directory</context>
<context>.htaccess</context></contextlist>
<override>FileInfo</override>
<usage>
<p>This directive specifies the name of the character set that
will be added to any response that does not have any parameter on
the content type in the HTTP headers. This will override any
character set specified in the body of the document via a
<code>META</code> tag. A setting of <code>AddDefaultCharset
Off</code> disables this
functionality. <code>AddDefaultCharset On</code> enables
Apache's internal default charset of <code>iso-8859-1</code> as
required by the directive. You can also specify an alternate
<var>charset</var> to be used. For example:</p>
<example>
AddDefaultCharset utf-8
</example>
</usage>
</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</compatibility>
<usage>
<p>This directive activates a particular output <a
href="../filter.html">filter</a> for a request depending on the
response MIME-type.</p>
<p>The following example uses the DEFLATE filter, which is provided by
<module>mod_deflate</module>. It will compress all output (either static
or dynamic) which is labeled as <code>text/html</code> or
<code>text/plain</code> before it is sent to the client.</p>
<example>
AddOutputFilterByType DEFLATE text/html text/plain
</example>
<p>If you want the content to be processed by more than one filter, they
have to be separated by semicolons. It's also possible to use one
<directive>AddOutputFilterByType</directive> directive for each of
them.</p>
<p>The configuration below causes all script output labeled as
<code>text/html</code> to be processed at first by the INCLUDES filter
and then by the DEFLATE filter.</p>
<example>
&lt;Location /cgi-bin/&gt;<br />
<indent>
Options Includes<br />
AddOutputFilterByType INCLUDES;DEFLATE text/html<br />
</indent>
&lt;/Location&gt;
</example>
<note><title>Note:</title>
<p>The output filters are not applied on proxy requests.</p>
</note>
</usage>
<seealso><directive module="mod_mime">AddOutputFilter</directive></seealso>
<seealso><directive module="core">SetOutputFilter</directive></seealso>
<seealso><module>mod_include</module></seealso>
<seealso><module>mod_deflate</module></seealso>
<seealso><a href="../filter.html">The filters documentation</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AllowOverride</name>
<description>Types of directives that are allowed in
.htaccess 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 .htaccess file (as specified by <directive
module="core">AccessFileName</directive>) it needs to know
which directives declared in that file can override earlier
access information.</p>
<p>When this directive is set to <code>None</code>, then
.htaccess files are completely ignored. In this case, the
server will not even attempt to read .htaccess 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
.htaccess 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>).</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</dt>
<dd>
Allow use of the directives controlling specific directory
features (<directive module="core">Options</directive> and
<directive module="mod_include">XBitHack</directive>).</dd>
</dl>
<p>Example:</p>
<example>
AllowOverride AuthConfig Indexes
</example>
</usage>
<seealso><directive module="core">AccessFileName</directive></seealso>
<seealso><a href="../configuring.html">Configuration Files</a></seealso>
<seealso><a href="../howto/htaccess.html">.htaccess Files</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AuthName</name>
<description>Authorization realm for use in HTTP
authentication</description>
<syntax>AuthName <var>auth-domain</var></syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>This directive sets the name of the authorization realm for a
directory. This realm is given to the client so that the user
knows which username and password to send.
<directive>AuthName</directive> takes a single argument; if the
realm name contains spaces, it must be enclosed in quotation
marks. It must be accompanied by <directive
module="core">AuthType</directive> and <directive
module="core">Require</directive> directives, and directives such
as <directive module="mod_authn_file">AuthUserFile</directive> and
<directive module="mod_authz_groupfile">AuthGroupFile</directive> to
work.</p>
<p>For example:</p>
<example>
AuthName "Top Secret"
</example>
<p>The string provided for the <code>AuthName</code> is what will
appear in the password dialog provided by most browsers.</p>
</usage>
<seealso><a
href="../howto/auth.html">Authentication, Authorization, and
Access Control</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>AuthType</name>
<description>Type of user authentication</description>
<syntax>AuthType Basic|Digest</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>This directive selects the type of user authentication for a
directory. Only <code>Basic</code> and <code>Digest</code> are
currently implemented.
It must be accompanied by <directive
module="core">AuthName</directive> and <directive
module="core">Require</directive> directives, and directives such
as <directive module="mod_authn_file">AuthUserFile</directive> and
<directive module="mod_authz_groupfile">AuthGroupFile</directive> to
work.</p>
</usage>
<seealso><a href="../howto/auth.html">Authentication, Authorization,
and Access Control</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>CGIMapExtension</name>
<description>Technique for locating the interpreter for CGI
scripts</description>
<syntax>CGIMapExtension cgi-path .extension</syntax>
<default>None</default>
<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 <code>CGIMapExtension sys:\foo.nlm .foo</code> will
cause all CGI script files with a .foo extension to be passed to the FOO interpreter.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ContentDigest</name>
<description>Enables the generation of Content-MD5 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 core, 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>
<default>DefaultType text/plain</default>
<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 MIME types
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>
DefaultType image/gif
</example>
<p>would be appropriate for a directory which contained many gif
images with filenames missing the .gif extension.</p>
<p>Note that unlike <directive
module="core">ForceType</directive>, this directive is 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>&lt;Directory <var>directory-path</var>&gt;
... &lt;/Directory&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p><directive type="section">Directory</directive> and
<code>&lt;/Directory&gt;</code> are used to enclose a group of
directives that will apply only to the named directory 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, `?' matches any
single character, and `*' matches any sequences of characters.
You may also use `[]' character ranges. None of the wildcards
match a `/' character, so <code>&lt;Directory
/*/public_html&gt;</code> will not match
<code>/home/user/public_html</code>, but <code>&lt;Directory
/home/*/public_html&gt;</code> will match. Example:</p>
<example>
&lt;Directory /usr/local/httpd/htdocs&gt;<br />
<indent>
Options Indexes FollowSymLinks<br />
</indent>
&lt;/Directory&gt;
</example>
<note>
<p>Be careful with the <var>directory-path</var> arguments:
They have to literally match the filesystem path which Apache uses
to access the files. Directives applied to a particular
&lt;Directory&gt; will not apply to files accessed from that same
directory via a different path, such as via different symbolic
links.</p>
</note>
<p>Extended regular
expressions can also be used, with the addition of the
<code>~</code> character. For example:</p>
<example>
&lt;Directory ~ "^/www/.*/[0-9]{3}"&gt;
</example>
<p>would match directories in /www/ that consisted of three
numbers.</p>
<p>If multiple (non-regular expression) directory sections
match the directory (or its parents) containing a document,
then the directives are applied in the order of shortest match
first, interspersed with the directives from the <a
href="#accessfilename">.htaccess</a> files. For example,
with</p>
<example>
&lt;Directory /&gt;<br />
<indent>
AllowOverride None<br />
</indent>
&lt;/Directory&gt;<br />
<br />
&lt;Directory /home/&gt;<br />
<indent>
AllowOverride FileInfo<br />
</indent>
&lt;/Directory&gt;
</example>
<p>for access to the document <code>/home/web/dir/doc.html</code>
the steps are:</p>
<ul>
<li>Apply directive <code>AllowOverride None</code>
(disabling <code>.htaccess</code> files).</li>
<li>Apply directive <code>AllowOverride FileInfo</code> (for
directory <code>/home/web</code>).</li>
<li>Apply any FileInfo directives in
<code>/home/web/.htaccess</code></li>
</ul>
<p>Regular expressions are not considered until after all of the
normal sections have been applied. Then all of the regular
expressions are tested in the order they appeared in the
configuration file. For example, with</p>
<example>
&lt;Directory ~ abc$&gt;<br />
<indent>
# ... directives here ...<br />
</indent>
&lt;/Directory&gt;
</example>
<p>The regular expression section won't be considered until after
all normal &lt;Directory&gt;s and <code>.htaccess</code> files
have been applied. Then the regular expression will match on
<code>/home/abc/public_html/abc</code> and be applied.</p>
<p><strong>Note that the default Apache access for
&lt;Directory /&gt; 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>
&lt;Directory /&gt;<br />
<indent>
Order Deny,Allow<br />
Deny from All<br />
</indent>
&lt;/Directory&gt;
</example>
<p><strong>and then override this for directories you
<em>want</em> accessible. See the <a
href="../misc/security_tips.html">Security Tips</a> page for more
details.</strong></p>
<p>The directory sections typically occur in
the access.conf file, but they may appear in any configuration
file. <directive type="section">Directory</directive> directives
cannot nest, and cannot appear in a <directive module="core"
type="section">Limit</directive> or <directive module="core"
type="section">LimitExcept</directive> section.</p>
</usage>
<seealso><a href="../sections.html">How
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 type="section">
<name>DirectoryMatch</name>
<description>Enclose directives that apply to
file-system directories matching a regular expression and their
subdirectories</description>
<syntax>&lt;DirectoryMatch <var>regex</var>&gt;
... &lt;/Directory&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p><directive type="section">DirectoryMatch</directive> and
<code>&lt;/DirectoryMatch&gt;</code> are used to enclose a group
of directives which will apply only to the named directory and
sub-directories of that directory, the same as <directive
module="core" type="section">Directory</directive>. However, it
takes as an argument a regular expression. For example:</p>
<example>
&lt;DirectoryMatch "^/www/.*/[0-9]{3}"&gt;
</example>
<p>would match directories in <code>/www/</code> that consisted of three
numbers.</p>
</usage>
<seealso><directive type="section" module="core">Directory</directive> for
a description of how regular expressions are mixed in with normal
<code>&lt;Directory&gt;</code>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>
<default>DocumentRoot /usr/local/apache/htdocs</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>This directive sets the directory from which httpd will
serve files. Unless matched by a directive like Alias, the
server appends the path from the requested URL to the document
root to make the path to the document. Example:</p>
<example>
DocumentRoot /usr/web
</example>
<p>then an access to
<code>http://www.my.host.com/index.html</code> refers to
<code>/usr/web/index.html</code>.</p>
<p>The <directive>DocumentRoot</directive> should be specified without
a trailing slash.</p>
</usage>
<seealso><a href="../urlmapping.html">Mapping URLs to Filesystem
Location</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 httpd 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 httpd.</li>
<li>With an NFS-mounted <directive module="core">DocumentRoot</directive>,
the httpd may crash due to a segmentation fault if a file is deleted
or truncated while the httpd 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>
&lt;Directory "/path-to-nfs-files"&gt;
EnableMMAP off
&lt;/Directory&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>EnableSendfile</name>
<description>Use the kernel sendfile support to deliver files to the client</description>
<syntax>EnableSendfile on|off</syntax>
<default>EnableSendfile 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 httpd 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 seperate 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>With an NFS-mounted <directive module="core">DocumentRoot</directive>,
the kernel may be unable to serve the network file through
it's 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 mounted files, this feature may be disabled explicitly for
the offending files by specifying:</p>
<example>
&lt;Directory "/path-to-nfs-files"&gt;
EnableSendfile off
&lt;/Directory&gt;
</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
problem/error</li>
<li>redirect to an external <var>URL</var> to handle the
problem/error</li>
</ol>
<p>The first option is the default, while options 2-4 are
configured using the <directive>ErrorDocument</directive>
directive, which is followed by the HTTP response code and a URL
or a message. Apache will sometimes offer additional information
regarding the problem/error.</p>
<p>URLs can begin with a slash (/) for local URLs, or be a full
URL which the client can resolve. Alternatively, a message can
be provided to be displayed by the browser. Examples:</p>
<example>
ErrorDocument 500 http://foo.example.com/cgi-bin/tester<br />
ErrorDocument 404 /cgi-bin/bad_urls.pl<br />
ErrorDocument 401 /subscription_info.html<br />
ErrorDocument 403 "Sorry can't allow you access today"
</example>
<p>Note that when you specify an <directive>ErrorDocument</directive>
that points to a remote URL (ie. anything with a method such as
"http" 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
"ErrorDocument 401" directive then it must refer to a local
document.</strong></p>
<p>Microsoft Internet Explorer (MSIE) will 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 Knowledgebase article <a
href="http://support.microsoft.com/default.aspx?scid=kb;en-us;Q294807">Q294807</a>.</p>
<p>Prior to version 2.0, messages were indicated by prefixing
them with a single unmatched double quote character.</p>
</usage>
<seealso><a href="../custom-error.html">documentation of
customizable responses</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ErrorLog</name>
<description>Location where the server will log errors</description>
<syntax> ErrorLog <var>file-path</var>|syslog[:<var>facility</var>]</syntax>
<default>ErrorLog logs/error_log (Unix)
ErrorLog logs/error.log (Windows and OS/2)</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ErrorLog</directive> directive sets the name of
the file to which the server will log any errors it encounters. If
the <var>file-path</var> does not begin with a slash (/) then it is
assumed to be relative to the <directive
module="core">ServerRoot</directive>.</p>
<example><title>Example</title>
ErrorLog /var/log/httpd/error_log
</example>
<p>If the <var>file-path</var>
begins with a pipe (|) then it is assumed to be a command to spawn
to handle the error log.</p>
<example><title>Example</title>
ErrorLog "|/usr/local/bin/httpd_errors"
</example>
<p>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 logfiles are stored is writable by
anyone other than the user that starts the server.</p>
</usage>
<seealso><directive module="core">LogLevel</directive></seealso>
<seealso><a href="../logs.html">Apache Log Files</a></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 ETag (entity tag) response
header field when the document is based on a file. (The ETag
value is used in cache management to save network bandwidth.) In
Apache 1.3.22 and earlier, the ETag value was <em>always</em> formed
from the file's inode, size, and last-modified time (mtime). The
FileETag 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 ETag field will be included in the
response</dd>
</dl>
<p>The <code>INode</code>, <code>MTime</code>, and <code>Size</code>
keywords may be prefixed with either <code>+</code> or <code>-</code>,
which allow changes to be made to the default setting inherited
from a broader scope. Any keyword appearing without such a prefix
immediately and completely cancels the inherited setting.</p>
<p>If a directory's configuration includes
<code>FileETag&nbsp;INode&nbsp;MTime&nbsp;Size</code>, and a
subdirectory's includes <code>FileETag&nbsp;-INode</code>,
the setting for that subdirectory (which will be inherited by
any sub-subdirectories that don't override it) will be equivalent to
<code>FileETag&nbsp;MTime&nbsp;Size</code>.</p>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Files</name>
<description>Contains directives that apply to matched
filenames</description>
<syntax>&lt;Files <var>filename</var>&gt; ... &lt;/Files&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <directive type="section">Files</directive> directive
provides for access control by filename. It is comparable to the
<directive module="core" type="directive">Directory</directive>
directive and <directive module="core"
type="directive">Location</directive> directives. It should be
matched with a <code>&lt;/Files&gt;</code> directive. The
directives given within this section will be applied to any object
with a basename (last component of filename) matching the
specified filename. <directive type="section">Files</directive>
sections are processed in the order they appear in the
configuration file, after the <directive module="core"
type="section">Directory</directive> sections and
<code>.htaccess</code> files are read, but before <directive
type="section" module="core">Location</directive> sections. Note
that <directive type="section">Files</directive> can be nested
inside <directive type="section"
module="core">Directory</directive> sections to restrict the
portion of the filesystem they apply to.</p>
<p>The <var>filename</var> argument should include a filename, or
a wild-card string, where `?' matches any single character, and
`*' matches any sequences of characters. Extended regular
expressions can also be used, with the addition of the
<code>~</code> character. For example:</p>
<example>
&lt;Files ~ "\.(gif|jpe?g|png)$"&gt;
</example>
<p>would match most common Internet graphics formats. In Apache 1.3
and later, <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
.htaccess files. This allows users to control access to their own
files, at a file-by-file level.</p>
</usage>
<seealso><a href="../sections.html">How
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 type="section">
<name>FilesMatch</name>
<description>Contains directives that apply to regular-expression matched
filenames</description>
<syntax>&lt;FilesMatch <var>regex</var>&gt; ... &lt;/FilesMatch&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <directive type="section">FilesMatch</directive> directive
provides for access control by filename, just as the <directive
module="core" type="section">Files</directive> directive
does. However, it accepts a regular expression. For example:</p>
<example>
&lt;FilesMatch "\.(gif|jpe?g|png)$"&gt;
</example>
<p>would match most common Internet graphics formats.</p>
</usage>
<seealso><a href="../sections.html">How
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>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 ".gif", you
might want to use:</p>
<example>
ForceType image/gif
</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>
# force all files to be image/gif:<br />
&lt;Location /images&gt;<br />
<indent>
ForceType image/gif<br />
</indent>
&lt;/Location&gt;<br />
<br />
# but normal mime-type associations here:<br />
&lt;Location /images/mixed&gt;<br />
<indent>
ForceType none<br />
</indent>
&lt;/Location&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>HostnameLookups</name>
<description>Enables DNS lookups on client IP addresses</description>
<syntax>HostnameLookups on|off|double</syntax>
<default>HostnameLookups off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context></contextlist>
<usage>
<p>This directive enables DNS lookups so that host names can be
logged (and passed to CGIs/SSIs in <code>REMOTE_HOST</code>).
The value <code>double</code> refers to doing double-reverse
DNS. 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 off 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 <a
href="../programs/logresolve.html">logresolve</a>, provided in
the <var>/support</var> directory, can be used to look up host
names from logged IP addresses offline.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>IdentityCheck</name>
<description>Enables logging of the RFC1413 identity of the remote
user</description>
<syntax>IdentityCheck on|off</syntax>
<default>IdentityCheck off</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context></contextlist>
<usage>
<p>This directive enables RFC1413-compliant logging of the
remote user name for each connection, where the client machine
runs identd or something similar. This information is logged in
the access log.</p>
<p>The information should not be trusted in any way except for
rudimentary usage tracking.</p>
<p>Note that this can cause serious latency problems accessing
your server since every request requires one of these lookups
to be performed. When firewalls are involved each lookup might
possibly fail and add 30 seconds of latency to each hit. So in
general this is not very useful on public servers accessible
from the Internet.</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>&lt;IfDefine [!]<var>parameter-name</var>&gt; ...
&lt;/IfDefine&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <code>&lt;IfDefine <var>test</var>&gt;...&lt;/IfDefine&gt;
</code> section is used to mark directives that are conditional. The
directives within an <directive type="section">IfDefine</directive>
section are only processed if the <var>test</var> is true. If <var>
test</var> is false, everything between the start and end markers is
ignored.</p>
<p>The <var>test</var> in the <directive type="section"
>IfDefine</directive> section directive can be one of two forms:</p>
<ul>
<li><var>parameter-name</var></li>
<li><code>!</code><var>parameter-name</var></li>
</ul>
<p>In the former case, the directives between the start and end
markers are only processed if the parameter named
<var>parameter-name</var> is defined. The second format reverses
the test, and only processes the directives if
<var>parameter-name</var> is <strong>not</strong> defined.</p>
<p>The <var>parameter-name</var> argument is a define as given on
the <code>httpd</code> 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 />
&lt;IfDefine ReverseProxy&gt;<br />
<indent>
LoadModule rewrite_module modules/mod_rewrite.so<br />
LoadModule proxy_module modules/libproxy.so<br />
</indent>
&lt;/IfDefine&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>IfModule</name>
<description>Encloses directives that are processed conditional on the
presence or absence of a specific module</description>
<syntax>&lt;IfModule [!]<var>module-name</var>&gt; ...
&lt;/IfModule&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>The <code>&lt;IfModule <var>test</var>&gt;...&lt;/IfModule&gt;</code>
section is used to mark directives that are conditional on the presence of a
specific module. The directives within an <directive type="section"
>IfModule</directive> section are only processed if the <var>test</var>
is true. If <var>test</var> is false, everything between the start and
end markers is ignored.</p>
<p>The <var>test</var> in the <directive type="section"
>IfModule</directive> section directive can be one of two forms:</p>
<ul>
<li><var>module name</var></li>
<li>!<var>module name</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
name</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 name</var> is
<strong>not</strong> included.</p>
<p>The <var>module name</var> argument is the file name of the
module, at the time it was compiled. For example,
<code>mod_rewrite.c</code>. If a module consists of several
source files, use the name of the file containing the string
<code>STANDARD20_MODULE_STUFF</code>.</p>
<p><directive type="section">IfModule</directive> sections are
nest-able, which can be used to implement simple multiple-module
tests.</p>
<note>This section should only be used if you need to have one
configuration file that works whether or not a specific module
is available. In normal operation, directives need not be
placed in <directive type="section">IfModule</directive>
sections.</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>Include</name>
<description>Includes other configuration files from within
the server configuration files</description>
<syntax>Include <var>file-path</var>|<var>directory-path</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context>
</contextlist>
<usage>
<p>This directive allows inclusion of other configuration files
from within the server configuration files.</p>
<p>If <directive>Include</directive> points to a directory, rather than a
file, Apache will read all files in that directory and any
subdirectory in alphabetical order, and parse those as configuration
files.</p>
<p>The file path specified may be a fully qualified path (i.e.
starting with a slash), or may be relative to the
<directive module="core">ServerRoot</directive> directory.</p>
<p>Examples:</p>
<example>
Include /usr/local/apache/conf/ssl.conf<br />
Include /usr/local/apache/conf/vhosts/
</example>
<p>Or, providing paths relative to your <code>ServerRoot</code>
directory:</p>
<example>
Include conf/ssl.conf<br />
Include conf/vhosts/
</example>
<p>Make sure that an included directory does not contain any stray
files, such as editor temporary files, for example, as Apache will
attempt to read them in and use the contents as configuration
directives, which may cause the server to fail on start up.
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 />
Processing config directory: /usr/local/apache/conf/vhosts<br />
Processing config file: /usr/local/apache/conf/vhosts/vhost1<br />
Processing config file: /usr/local/apache/conf/vhosts/vhost2<br />
Syntax OK
</example>
<p>This will help in verifying that you are getting only the files
that you intended as part of your configuration.</p>
</usage>
<seealso><a href="../programs/apachectl.html">apachectl</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>KeepAlive</name>
<description>Enables HTTP persistent connections</description>
<syntax>KeepAlive on|off</syntax>
<default>KeepAlive On</default>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The Keep-Alive extension to HTTP/1.0 and the persistent
connection feature of HTTP/1.1 provide long-lived HTTP sessions
which allow multiple requests to be sent over the same TCP
connection. In some cases this has been shown to result in an
almost 50% speedup in latency times for HTML documents with
many images. To enable Keep-Alive connections in Apache 1.2 and
later, set <code>KeepAlive On</code>.</p>
<p>For HTTP/1.0 clients, Keep-Alive connections will only be
used if they are specifically requested by a client. In
addition, a Keep-Alive connection with an HTTP/1.0 client can
only be used when the length of the content is known in
advance. This implies that dynamic content such as CGI output,
SSI pages, and server-generated directory listings will
generally not use Keep-Alive connections to HTTP/1.0 clients.
For HTTP/1.1 clients, persistent connections are the default
unless otherwise specified. If the client requests it, chunked
encoding will be used in order to send content of unknown
length over persistent connections.</p>
</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 15</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>&lt;Limit <var>method</var> [<var>method</var>] ... &gt; ...
&lt;/Limit&gt;</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 <code>&lt;Limit&gt;</code>
bracket <strong>will have no effect</strong>. The following
example applies the access control only to the methods POST, PUT,
and DELETE, leaving all other methods unprotected:</p>
<example>
&lt;Limit POST PUT DELETE&gt;<br />
<indent>
Require valid-user<br />
</indent>
&lt;/Limit&gt;
</example>
<p>The method names listed can be one or more of: <code>GET</code>,
<code>POST</code>, <code>PUT</code>, <code>DELETE</code>,
<code>CONNECT</code>, <code>OPTIONS</code>, <code>TRACE</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.</p>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>LimitExcept</name>
<description>Restrict access controls to all HTTP methods
except the named ones</description>
<syntax>&lt;LimitExcept <var>method</var> [<var>method</var>] ... &gt; ...
&lt;/LimitExcept&gt;</syntax>
<contextlist><context>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>&lt;/LimitExcept&gt;</code> are used to enclose
a group of access control directives which will then apply to any
HTTP access method <strong>not</strong> listed in the arguments;
i.e., it is the opposite of a <directive type="section"
module="core">Limit</directive> section and can be used to control
both standard and nonstandard/unrecognized methods. See the
documentation for <directive module="core"
type="section">Limit</directive> for more details.</p>
<p>For example:</p>
<example>
&lt;LimitExcept POST GET&gt;<br />
<indent>
Require valid-user<br />
</indent>
&lt;LimitExcept&gt;
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>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. The default value is defined by the compile-time
constant <code>DEFAULT_LIMIT_REQUEST_BODY</code> (0 as
distributed).</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 passing form information to the
server. Implementations of the PUT 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 wich 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> from 0
to the value of the compile-time constant
<code>DEFAULT_LIMIT_REQUEST_FIELDSIZE</code> (8190 as
distributed) that will be allowed in an HTTP request
header.</p>
<p>The <directive>LimitRequestFieldsize</directive> directive
allows the server administrator to reduce the limit on the allowed
size of an HTTP request header field below the normal input buffer
size compiled with the server. 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.</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 16380
</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> from 0 to
the value of the compile-time constant
<code>DEFAULT_LIMIT_REQUEST_LINE</code> (8190 as distributed)
that will be allowed on the HTTP request-line.</p>
<p>The <directive>LimitRequestLine</directive> directive allows
the server administrator to reduce the limit on the allowed size
of a client's HTTP request-line below the normal input buffer size
compiled with the server. 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 GET 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 16380
</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>number</var></syntax>
<default>LimitXMLRequestBody 1000000</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>All</override>
<usage>
<p>Limit (in bytes) on maximum size of an XML-based request
body. A value of <code>0</code> will disable any checking.</p>
<p>Example:</p>
<example>
LimitXMLRequestBody 0
</example>
</usage>
</directivesynopsis>
<directivesynopsis type="section">
<name>Location</name>
<description>Applies the enclosed directives only to matching
URLs</description>
<syntax>&lt;Location
URL-path|URL&gt; ... &lt;/Location&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive type="section">Location</directive> directive
provides for access control by URL. It is similar to the
<directive type="section" module="core">Directory</directive>
directive, and starts a subsection which is terminated with a
<code>&lt;/Location&gt;</code> directive. <directive
type="section">Location</directive> sections are processed in the
order they appear in the configuration file, after the <directive
type="section" module="core">Directory</directive> sections and
<code>.htaccess</code> files are read, and after the <directive
type="section" module="core">Files</directive> sections.</p>
<p>Note that URLs do not have to line up with the filesystem at
all, it should be emphasized that &lt;Location&gt; operates
completely outside the filesystem.</p>
<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
<code>scheme://servername/path</code>, and you must include the
prefix.</p>
<p>The URL may use wildcards In a wild-card string, `?' matches
any single character, and `*' matches any sequences of
characters.</p>
<p>Extended regular
expressions can also be used, with the addition of the
<code>~</code> character. For example:</p>
<example>
&lt;Location ~ "/(extra|special)/data"&gt;
</example>
<p>would match URLs that contained the substring "/extra/data" or
"/special/data". In Apache 1.3 and above, a new directive
<directive type="section" module="core">LocationMatch</directive>
exists which 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
only from browsers at foo.com, you might use:</p>
<example>
&lt;Location /status&gt;<br />
<indent>
SetHandler server-status<br />
Order Deny,Allow<br />
Deny from all<br />
Allow from .foo.com<br />
</indent>
&lt;/Location&gt;
</example>
<note><title>Note about / (slash)</title>
<p>The slash character has special meaning depending on where in a
URL it appears. People may be used to its behavior in the filesystem
where multiple adjacent slashes are frequently collapsed to a single
slash (<em>i.e.</em>, <code>/home///foo</code> is the same as
<code>/home/foo</code>). In URL-space this is not necessarily true.
The <directive type="section" module="core">LocationMatch</directive>
directive and the regex version of <directive type="section"
>Location</directive> require you to explicitly specify multiple
slashes if that is your intention.</p>
<p>For example, <code>&lt;LocationMatch ^/abc&gt;</code> would match
the request URL <code>/abc</code> but not the request URL <code>
//abc</code>. The (non-regex) <directive type="section"
>Location</directive> directive behaves similarly when used for
proxy requests. But when (non-regex) <directive type="section"
>Location</directive> is used for non-proxy requests it will
implicitly match multiple slashes with a single slash. For example,
if you specify <code>&lt;Location /abc/def&gt;</code> and the
request is to <code>/abc//def</code> then it will match.</p>
</note>
</usage>
<seealso><a href="../sections.html">How
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 type="section">
<name>LocationMatch</name>
<description>Applies the enclosed directives only to regular-expression
matching URLs</description>
<syntax>&lt;LocationMatch
<var>regex</var>&gt; ... &lt;/Location&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive type="section">LocationMatch</directive> directive
provides for access control by URL, in an identical manner to
<directive module="core" type="section">Location</directive>. However,
it takes a regular expression as an argument instead of a simple
string. For example:</p>
<example>
&lt;LocationMatch "/(extra|special)/data"&gt;
</example>
<p>would match URLs that contained the substring <code>/extra/data</code>
or <code>/special/data</code>.</p>
</usage>
<seealso><a href="../sections.html">How
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>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">
<tr>
<th><strong>Level</strong> </th>
<th><strong>Description</strong> </th>
<th><strong>Example</strong> </th>
</tr>
<tr>
<td><code>emerg</code> </td>
<td>Emergencies - system is unusable.</td>
<td>"Child cannot open lock file. Exiting"</td>
</tr>
<tr>
<td><code>alert</code> </td>
<td>Action must be taken immediately.</td>
<td>"getpwuid: couldn't determine user name from uid"</td>
</tr>
<tr>
<td><code>crit</code> </td>
<td>Critical Conditions.</td>
<td>"socket: Failed to get a socket, exiting child"</td>
</tr>
<tr>
<td><code>error</code> </td>
<td>Error conditions.</td>
<td>"Premature end of script headers"</td>
</tr>
<tr>
<td><code>warn</code> </td>
<td>Warning conditions.</td>
<td>"child process 1234 did not exit, sending another
SIGHUP"</td>
</tr>
<tr>
<td><code>notice</code> </td>
<td>Normal but significant condition.</td>
<td>"httpd: caught SIGBUS, attempting to dump core in
..."</td>
</tr>
<tr>
<td><code>info</code> </td>
<td>Informational.</td>
<td>"Server seems busy, (you may need to increase
StartServers, or Min/MaxSpareServers)..."</td>
</tr>
<tr>
<td><code>debug</code> </td>
<td>Debug-level messages</td>
<td>"Opening config file ..."</td>
</tr>
</table>
<p>When a particular level is specified, messages from all
other levels of higher significance will be reported as well.
<em>E.g.</em>, when <code>LogLevel info</code> is specified,
then messages with log levels of <code>notice</code> and
<code>warn</code> will also be posted.</p>
<p>Using a level of at least <code>crit</code> is
recommended.</p>
<p>For example:</p>
<example>
LogLevel notice
</example>
</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
href="../vhosts/">name-based virtual hosts</a>.</p>
<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>
<p>Note: the "main server" and any _default_ 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 VirtualHosts for that address).</p>
<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 [fe80::a00:20ff:fea7:ccea]:8080
</example>
<p>To receive requests on all interfaces, you can use an argument of
*</p>
<example>
NameVirtualHost *
</example>
<note><title>Argument to &lt;VirtualHost&gt; directive</title>
<p>Note that the argument to the &lt;VirtualHost&gt; directive must
exactly match the argument to the <directive
>NameVirtualHost</directive> directive.</p>
<example>
NameVirtualHost 1.2.3.4<br />
&lt;VirtualHost 1.2.3.4&gt;<br />
# ...<br />
&lt;/VirtualHost&gt;<br />
</example>
</note>
</usage>
<seealso><a href="../vhosts/">Virtual Hosts
documentation</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>Options</name>
<description>Configures what features are available in a particular
directory</description>
<syntax>Options
[+|-]<var>option</var> [[+|-]<var>option</var>] ...</syntax>
<default>Options All</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>Options</override>
<usage>
<p>The <directive>Options</directive> directive controls which
server features are available in a particular directory.</p>
<p><var>option</var> can be set to <code>None</code>, in which
case none of the extra features are enabled, or one or more of
the following:</p>
<dl>
<dt>All</dt>
<dd>All options except for MultiViews. This is the default
setting.</dd>
<dt>ExecCGI</dt>
<dd>
Execution of CGI scripts is permitted.</dd>
<dt>FollowSymLinks</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>Includes</dt>
<dd>
Server-side includes are permitted.</dd>
<dt>IncludesNOEXEC</dt>
<dd>
Server-side includes are permitted, but the #exec command and
#exec CGI are disabled. It is still possible to #include
virtual CGI scripts from ScriptAliase'd directories.</dd>
<dt>Indexes</dt>
<dd>
If a URL which maps to a directory is requested, and the
there is no DirectoryIndex (<em>e.g.</em>, index.html) in
that directory, then the server will return a formatted
listing of the directory.</dd>
<dt>MultiViews</dt>
<dd>
<a href="../content-negotiation.html">Content negotiated</a>
MultiViews are allowed.</dd>
<dt>SymLinksIfOwnerMatch</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.<br
/> <strong>Note</strong>: this option gets ignored if set inside
a <directive module="core" type="section">Location</directive>
section.</dd>
</dl>
<p>Normally, if multiple <directive>Options</directive> could apply to a
directory, then the most specific one is taken complete; the
options are not merged. However if <em>all</em> the options on
the <directive>Options</directive> directive are preceded by a + or -
symbol, the options are merged. Any options preceded by a + are
added to the options currently in force, and any options
preceded by a - are removed from the options currently in
force. </p>
<p>For example, without any + and - symbols:</p>
<example>
&lt;Directory /web/docs&gt;<br />
<indent>
Options Indexes FollowSymLinks<br />
</indent>
&lt;/Directory&gt;<br />
<br />
&lt;Directory /web/docs/spec&gt;<br />
<indent>
Options Includes<br />
</indent>
&lt;/Directory&gt;
</example>
<p>then only <code>Includes</code> will be set for the
/web/docs/spec directory. However if the second
<directive>Options</directive> directive uses the + and - symbols:</p>
<example>
&lt;Directory /web/docs&gt;<br />
<indent>
Options Indexes FollowSymLinks<br />
</indent>
&lt;/Directory&gt;<br />
<br />
&lt;Directory /web/docs/spec&gt;<br />
<indent>
Options +Includes -Indexes<br />
</indent>
&lt;/Directory&gt;
</example>
<p>then the options <code>FollowSymLinks</code> and
<code>Includes</code> are set for the /web/docs/spec directory.</p>
<p><strong>Note:</strong> Using <code>-IncludesNOEXEC</code> or
<code>-Includes</code> disables server-side includes completely
regardless of the previous setting.</p>
<p>The default in the absence of any other settings is
<code>All</code>.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>Require</name>
<description>Selects which authenticated users can access
a resource</description>
<syntax>Require <var>entity-name</var> [<var>entity-name</var>] ...</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>This directive selects which authenticated users can access
a directory. The allowed syntaxes are:</p>
<ul>
<li>
Require user <var>userid</var> [<var>userid</var>] ...
<p>Only the named users can access the directory.</p>
</li>
<li>
Require group <var>group-name</var> [<var>group-name</var>] ...
<p>Only users in the named groups can access the
directory.</p>
</li>
<li>
Require valid-user
<p>All valid users can access the directory.</p>
</li>
</ul>
<p><directive>Require</directive> must be accompanied by
<directive module="core">AuthName</directive> and <directive
module="core">AuthType</directive> directives, and directives such
as <directive module="mod_authn_file">AuthUserFile</directive>
and <directive module="mod_authz_groupfile">AuthGroupFile</directive> (to
define users and groups) in order to work correctly. Example:</p>
<example>
AuthType Basic<br />
AuthName "Restricted Directory"<br />
AuthUserFile /web/users<br />
AuthGroupFile /web/groups<br />
Require group admin
</example>
<p>Access controls which are applied in this way are effective for
<strong>all</strong> methods. <strong>This is what is normally
desired.</strong> If you wish to apply access controls only to
specific methods, while leaving other methods unprotected, then
place the <directive>Require</directive> statement into a
<directive module="core" type="section">Limit</directive>
section.</p>
</usage>
<seealso><directive module="core">Satisfy</directive></seealso>
<seealso><module>mod_authz_host</module></seealso>
</directivesynopsis>
<directivesynopsis>
<name>RLimitCPU</name>
<description>Limits the CPU consumption of processes launched
by Apache children</description>
<syntax>RLimitCPU <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 root, 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>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 root, 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 root, 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>
<p>Note: If CGI processes are <strong>not</strong> running
under userids other than the web server userid, 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
error_log.</p>
</usage>
<seealso><directive module="core">RLimitMEM</directive></seealso>
<seealso><directive module="core">RLimitCPU</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>Satisfy</name>
<description>Interaction between host-level access control and
user authentication</description>
<syntax>Satisfy any|all</syntax>
<default>Satisfy all</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>Access policy if both <directive
module="mod_authz_host">Allow</directive> and <directive
module="core">Require</directive> used. The parameter can be
either <var>all</var> or <var>any</var>. This directive is only
useful if access to a particular area is being restricted by both
username/password <em>and</em> client host address. In this case
the default behavior (<var>all</var>) is to require that the client passes
the address access restriction <em>and</em> enters a valid
username and password. With the "any" option the client will be
granted access if they either pass the host restriction or enter a
valid username and password. This can be used to password restrict
an area, but to let clients from particular addresses in without
prompting for a password.</p>
<p>For example, if you wanted to let people on your network have
unrestricted access to a portion of your website, but require that
people outside of your network provide a password, you could use a
configuration similar to the following:</p>
<example>
Require valid-user<br />
Allow from 192.168.1<br />
Satisfy any
</example>
</usage>
<seealso><directive module="mod_authz_host">Allow</directive></seealso>
<seealso><directive module="core">Require</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ScriptInterpreterSource</name>
<description>Technique for locating the interpreter for CGI
scripts</description>
<syntax>ScriptInterpreterSource registry|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</compatibility>
<usage>
<p>This directive is used to control how Apache finds the
interpreter used to run CGI scripts. The default technique is to
use the interpreter pointed to by the #! line in the
script. Setting <code>ScriptInterpreterSource registry</code> will
cause the Windows Registry to be searched using the script file
extension (e.g., .pl) as a search key.</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></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<usage>
<p>The <directive>ServerAdmin</directive> sets the e-mail address
that the server includes in any error messages it returns to the
client.</p>
<p>It may be worth setting up a dedicated address for this, e.g.</p>
<example>
ServerAdmin www-admin@foo.example.com
</example>
<p>as users do not always mention that they are talking about the
server!</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ServerAlias</name>
<description>Alternate names for a host used when matching requests
to name-virtual hosts</description>
<syntax>ServerAlias <var>hostname</var> [<var>hostname</var>] ...</syntax>
<contextlist><context>virtual host</context></contextlist>
<usage>
<p>The <directive>ServerAlias</directive> directive sets the
alternate names for a host, for use with <a
href="../vhosts/name-based.html">name-based virtual hosts</a>.</p>
<example>
&lt;VirtualHost *&gt;<br />
ServerName server.domain.com<br />
ServerAlias server server2.domain.com server2<br />
# ...<br />
&lt;/VirtualHost&gt;
</example>
</usage>
<seealso><a href="../vhosts/">Apache Virtual Host documentation</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ServerName</name>
<description>Hostname and port that the server uses to identify
itself</description>
<syntax>ServerName <var>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 hostname and
port that the server uses to identify itself. This is used when
creating redirection URLs. For example, if the name of the
machine hosting the webserver is <code>simple.example.com</code>,
but the machine also has the DNS alias <code>www.example.com</code>
and you wish the webserver 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
servername, 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>See the description of the
<directive module="core">UseCanonicalName</directive> directive for
settings which determine whether self-referential URL's (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>
<seealso><a href="../dns-caveats.html">DNS Issues</a></seealso>
<seealso><a href="../vhosts/">Apache virtual host
documentation</a></seealso>
<seealso><directive module="core">UseCanonicalName</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-virtual host that
is accessed by an incompatible browser</description>
<syntax>ServerPath <var>URL-path</var></syntax>
<contextlist><context>virtual host</context></contextlist>
<usage>
<p>The <directive>ServerPath</directive> directive sets the legacy
URL pathname for a host, for use with <a
href="../vhosts/">name-based virtual hosts</a>.</p>
</usage>
<seealso><a href="../vhosts/">Apache Virtual Host documentation</a></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ServerRoot</name>
<description>Base directory for the server installation</description>
<syntax>ServerRoot <var>directory-path</var></syntax>
<default>ServerRoot /usr/local/apache</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>ServerRoot</directive> directive sets the
directory in which the server lives. Typically it will contain the
subdirectories <code>conf/</code> and <code>logs/</code>. Relative
paths for other configuration files are taken as relative to this
directory.</p>
<example><title>Example</title>
ServerRoot /home/httpd
</example>
</usage>
<seealso><a href="../invoking.html">the <code>-d</code>
option to <code>httpd</code></a></seealso>
<seealso><a href="../misc/security_tips.html#serverroot">the
security tips</a> for information on how to properly set
permissions on the ServerRoot</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, mod_proxy ftp directory listings,
mod_info 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.<br /> The <code>Off</code>
setting, which is the default, suppresses the error 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 ServerTokens directive.</p>
</usage>
<seealso><directive module="core">ServerTokens</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>ServerTokens</name>
<description>Configures the Server HTTP response header</description>
<syntax>ServerTokens Major|Minor|Minimal|ProductOnly|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>
<dd>Server sends (<em>e.g.</em>): <code>Server:
Apache</code></dd>
<dt><code>ServerTokens Major</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server:
Apache/2</code></dd>
<dt><code>ServerTokens Minor</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server:
Apache/2.0</code></dd>
<dt><code>ServerTokens Min[imal]</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server:
Apache/2.0.41</code></dd>
<dt><code>ServerTokens OS</code></dt>
<dd>Server sends (<em>e.g.</em>): <code>Server: Apache/2.0.41
(Unix)</code></dd>
<dt><code>ServerTokens Full</code> (or not specified)</dt>
<dd>Server sends (<em>e.g.</em>): <code>Server: Apache/2.0.41
(Unix) PHP/4.2.2 MyMod/1.2</code></dd>
</dl>
<p>This setting applies to the entire server, and cannot be
enabled or disabled on a virtualhost-by-virtualhost basis.</p>
<p>After version 2.0.44, this directive also controls the
information presented by the ServerSignature 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
through the <a href="../handler.html">handler</a> given by
<var>handler-name</var>. For example, if you had a directory you
wanted to be parsed entirely as imagemap rule files, regardless
of extension, you might put the following into an
<code>.htaccess</code> file in that directory:</p>
<example>
SetHandler imap-file
</example>
<p>Another example: if you wanted to have the server display a
status report whenever a URL of
<code>http://servername/status</code> was called, you might put
the following into httpd.conf:</p>
<example>
&lt;Location /status&gt;<br />
<indent>
SetHandler server-status<br />
</indent>
&lt;/Location&gt;
</example>
</usage>
<seealso><directive module="mod_mime">AddHandler</directive></seealso>
</directivesynopsis>
<directivesynopsis>
<name>SetInputFilter</name>
<description>Sets the filters that will process client requests and POST
input</description>
<syntax>SetInputFilter <var>filter</var>[;<var>filter</var>...]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<usage>
<p>The <directive>SetInputFilter</directive> directive sets the
filter or filters which will process client requests and POST
input when they are received by the server. This is in addition to
any filters defined elsewhere, including the
<directive module="mod_mime">AddInputFilter</directive>
directive.</p>
<p>If more than one filter is specified, they must be separated
by semicolons in the order in which they should process the
content.</p>
</usage>
<seealso><a href="../filter.html">Filters</a> documentation</seealso>
</directivesynopsis>
<directivesynopsis>
<name>SetOutputFilter</name>
<description>Sets the filters that will process responses from the
server</description>
<syntax>SetOutputFilter <var>filter</var>[;<var>filter</var>...]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>FileInfo</override>
<usage>
<p>The <directive>SetOutputFilter</directive> directive sets the filters
which will process responses from the server before they are
sent to the client. This is in addition to any filters defined
elsewhere, including the
<directive module="mod_mime">AddOutputFilter</directive>
directive.</p>
<p>For example, the following configuration will process all files
in the <code>/www/data/</code> directory for server-side
includes.</p>
<example>
&lt;Directory /www/data/&gt;<br />
<indent>
SetOutputFilter INCLUDES<br />
</indent>
&lt;/Directory&gt;
</example>
<p>If more than one filter is specified, they must be separated
by semicolons in the order in which they should process the
content.</p>
</usage>
<seealso><a href="../filter.html">Filters</a> documentation</seealso>
</directivesynopsis>
<directivesynopsis>
<name>TimeOut</name>
<description>Amount of time the server will wait for
certain events before failing a request</description>
<syntax>TimeOut <var>number</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>UseCanonicalName</name>
<description>Configures how the server determines its own name and
port</description>
<syntax>UseCanonicalName on|off|dns</syntax>
<default>UseCanonicalName on</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
<code>http://www/splat</code>, <em>without the trailing
slash</em> then Apache will redirect them to
<code>http://www.domain.com/splat/</code>. If you have
authentication enabled, this will cause the user to have to
authenticate twice (once for <code>www</code> and once again
for <code>www.domain.com</code> -- see <a
href="http://httpd.apache.org/docs/misc/FAQ.html#prompted-twice">the
FAQ on this subject for more information</a>). But if
<directive>UseCanonicalName</directive> is set off, then Apache will
redirect to <code>http://www/splat/</code>.</p>
<p>There is a third option, <code>UseCanonicalName DNS</code>,
which is intended for use with mass IP-based virtual hosting to
support ancient clients that do not provide a
<code>Host:</code> header. With this option Apache 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">ServerName</directive></seealso>
<seealso><directive module="mpm_common">Listen</directive></seealso>
</directivesynopsis>
<directivesynopsis type="section">
<name>VirtualHost</name>
<description>Contains directives that apply only to a specific
hostname or IP address</description>
<syntax>&lt;VirtualHost
<var>addr</var>[:<var>port</var>] [<var>addr</var>[:<var>port</var>]]
...&gt; ... &lt;/VirtualHost&gt;</syntax>
<contextlist><context>server config</context></contextlist>
<usage>
<p><directive type="section">VirtualHost</directive> and
<code>&lt;/VirtualHost&gt;</code> are used to enclose a group of
directives that will apply only to a particular virtual host. Any
directive that is allowed in a virtual host context may be
used. When the server receives a request for a document on a
particular virtual host, it uses the configuration directives
enclosed in the <directive type="section">VirtualHost</directive>
section. <var>Addr</var> can be:</p>
<ul>
<li>The IP address of the virtual host;</li>
<li>A fully qualified domain name for the IP address of the
virtual host;</li>
<li>The character *, which is used only in combination with
<code>NameVirtualHost *</code> to match all IP addresses; or</li>
<li>The string <code>_default_</code>, which is used only
with IP virtual hosting to catch unmatched IP addresses.</li>
</ul>
<example><title>Example</title>
&lt;VirtualHost 10.1.2.3&gt;<br />
<indent>
ServerAdmin webmaster@host.foo.com<br />
DocumentRoot /www/docs/host.foo.com<br />
ServerName host.foo.com<br />
ErrorLog logs/host.foo.com-error_log<br />
TransferLog logs/host.foo.com-access_log<br />
</indent>
&lt;/VirtualHost&gt;
</example>
<p>IPv6 addresses must be specified in square brackets because
the optional port number could not be determined otherwise. An
IPv6 example is shown below:</p>
<example>
&lt;VirtualHost [fe80::a00:20ff:fea7:ccea]&gt;<br />
<indent>
ServerAdmin webmaster@host.example.com<br />
DocumentRoot /www/docs/host.example.com<br />
ServerName host.example.com<br />
ErrorLog logs/host.example.com-error_log<br />
TransferLog logs/host.example.com-access_log<br />
</indent>
&lt;/VirtualHost&gt;
</example>
<p>Each Virtual Host must correspond to a different IP address,
different port number or a different host name for the server,
in the former case the server machine must be configured to
accept IP packets for multiple addresses. (If the machine does
not have multiple network interfaces, then this can be
accomplished with the <code>ifconfig alias</code> command (if
your OS supports it).</p>
<note><title>Note</title>
<p>The use of <directive type="section">VirtualHost</directive> does
<strong>not</strong> affect what addresses Apache 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 _default_ 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 _default_ virtual host. See the <a
href="../vhosts/name-based.html">name-based virtual hosting</a>
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>
<p>See the <a href="../misc/security_tips.html">security tips</a>
document for details on why your security could be compromised if the
directory where logfiles are stored is writable by anyone other
than the user that starts the server.</p>
</note>
</usage>
<seealso><a href="../vhosts/">Apache Virtual Host documentation</a></seealso>
<seealso><a href="../dns-caveats.html">Warnings about DNS and
Apache</a></seealso>
<seealso><a href="../bind.html">Setting
which addresses and ports Apache uses</a></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>
</modulesynopsis>
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