core.html.en

    messages recorded in the error logs (see <code class="directive"><a href="#errorlog">ErrorLog</a></code> directive). The following
    <var>level</var>s are available, in order of decreasing
    significance:</p>

    <table class="bordered">
    
      <tr>
        <th><strong>Level</strong> </th>

        <th><strong>Description</strong> </th>

        <th><strong>Example</strong> </th>
      </tr>

      <tr>
        <td><code>emerg</code> </td>

        <td>Emergencies - system is unusable.</td>

        <td>"Child cannot open lock file. Exiting"</td>
      </tr>

      <tr>
        <td><code>alert</code> </td>

        <td>Action must be taken immediately.</td>

        <td>"getpwuid: couldn't determine user name from uid"</td>
      </tr>

      <tr>
        <td><code>crit</code> </td>

        <td>Critical Conditions.</td>

        <td>"socket: Failed to get a socket, exiting child"</td>
      </tr>

      <tr>
        <td><code>error</code> </td>

        <td>Error conditions.</td>

        <td>"Premature end of script headers"</td>
      </tr>

      <tr>
        <td><code>warn</code> </td>

        <td>Warning conditions.</td>

        <td>"child process 1234 did not exit, sending another
        SIGHUP"</td>
      </tr>

      <tr>
        <td><code>notice</code> </td>

        <td>Normal but significant condition.</td>

        <td>"httpd: caught SIGBUS, attempting to dump core in
        ..."</td>
      </tr>

      <tr>
        <td><code>info</code> </td>

        <td>Informational.</td>

        <td>"Server seems busy, (you may need to increase
        StartServers, or Min/MaxSpareServers)..."</td>
      </tr>

      <tr>
        <td><code>debug</code> </td>

        <td>Debug-level messages</td>

        <td>"Opening config file ..."</td>
      </tr>
      <tr>
        <td><code>trace1</code> </td>

        <td>Trace messages</td>

        <td>"proxy: FTP: control connection complete"</td>
      </tr>
      <tr>
        <td><code>trace2</code> </td>

        <td>Trace messages</td>

        <td>"proxy: CONNECT: sending the CONNECT request to the remote proxy"</td>
      </tr>
      <tr>
        <td><code>trace3</code> </td>

        <td>Trace messages</td>

        <td>"openssl: Handshake: start"</td>
      </tr>
      <tr>
        <td><code>trace4</code> </td>

        <td>Trace messages</td>

        <td>"read from buffered SSL brigade, mode 0, 17 bytes"</td>
      </tr>
      <tr>
        <td><code>trace5</code> </td>

        <td>Trace messages</td>

        <td>"map lookup FAILED: map=rewritemap key=keyname"</td>
      </tr>
      <tr>
        <td><code>trace6</code> </td>

        <td>Trace messages</td>

        <td>"cache lookup FAILED, forcing new map lookup"</td>
      </tr>
      <tr>
        <td><code>trace7</code> </td>

        <td>Trace messages, dumping large amounts of data</td>

        <td>"| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |"</td>
      </tr>
      <tr>
        <td><code>trace8</code> </td>

        <td>Trace messages, dumping large amounts of data</td>

        <td>"| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |"</td>
      </tr>
    </table>

    <p>When a particular level is specified, messages from all
    other levels of higher significance will be reported as well.
    <em>E.g.</em>, when <code>LogLevel info</code> is specified,
    then messages with log levels of <code>notice</code> and
    <code>warn</code> will also be posted.</p>

    <p>Using a level of at least <code>crit</code> is
    recommended.</p>

    <p>For example:</p>

    <pre class="prettyprint lang-config">LogLevel notice</pre>


    <div class="note"><h3>Note</h3>
      <p>When logging to a regular file, messages of the level
      <code>notice</code> cannot be suppressed and thus are always
      logged. However, this doesn't apply when logging is done
      using <code>syslog</code>.</p>
    </div>

    <p>Specifying a level without a module name will reset the level
    for all modules to that level.  Specifying a level with a module
    name will set the level for that module only. It is possible to
    use the module source file name, the module identifier, or the
    module identifier with the trailing <code>_module</code> omitted
    as module specification. This means the following three specifications
    are equivalent:</p>

    <pre class="prettyprint lang-config">LogLevel info ssl:warn
LogLevel info mod_ssl.c:warn
LogLevel info ssl_module:warn</pre>


    <p>It is also possible to change the level per directory:</p>

    <pre class="prettyprint lang-config">LogLevel info
&lt;Directory "/usr/local/apache/htdocs/app"&gt;
  LogLevel debug
&lt;/Directory&gt;</pre>


    <div class="note">
        Per directory loglevel configuration only affects messages that are
        logged after the request has been parsed and that are associated with
        the request. Log messages which are associated with the connection or
        the server are not affected.
    </div>

<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#errorlog">ErrorLog</a></code></li>
<li><code class="directive"><a href="#errorlogformat">ErrorLogFormat</a></code></li>
<li><a href="../logs.html">Apache HTTP Server Log Files</a></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="MaxKeepAliveRequests" id="MaxKeepAliveRequests">MaxKeepAliveRequests</a> <a name="maxkeepaliverequests" id="maxkeepaliverequests">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of requests allowed on a persistent
connection</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxKeepAliveRequests <var>number</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxKeepAliveRequests 100</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
</table>
    <p>The <code class="directive">MaxKeepAliveRequests</code> directive
    limits the number of requests allowed per connection when
    <code class="directive"><a href="#keepalive">KeepAlive</a></code> is on. If it is
    set to <code>0</code>, unlimited requests will be allowed. We
    recommend that this setting be kept to a high value for maximum
    server performance.</p>

    <p>For example:</p>

    <pre class="prettyprint lang-config">MaxKeepAliveRequests 500</pre>


</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="MaxRangeOverlaps" id="MaxRangeOverlaps">MaxRangeOverlaps</a> <a name="maxrangeoverlaps" id="maxrangeoverlaps">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of overlapping ranges (eg: <code>100-200,150-300</code>) allowed before returning the complete
        resource </td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRangeOverlaps default | unlimited | none | <var>number-of-ranges</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxRangeOverlaps 20</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.3.15 and later</td></tr>
</table>
        <p>The <code class="directive">MaxRangeOverlaps</code> directive
            limits the number of overlapping HTTP ranges the server is willing to
            return to the client. If more overlapping ranges than permitted are requested,
            the complete resource is returned instead.</p>

        <dl>
            <dt><strong>default</strong></dt>
            <dd>Limits the number of overlapping ranges to a compile-time default of 20.</dd>

            <dt><strong>none</strong></dt>
            <dd>No overlapping Range headers are allowed.</dd>

            <dt><strong>unlimited</strong></dt>
            <dd>The server does not limit the number of overlapping ranges it is
                willing to satisfy.</dd>

            <dt><var>number-of-ranges</var></dt>
            <dd>A positive number representing the maximum number of overlapping ranges the
                server is willing to satisfy.</dd>
        </dl>
    
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="MaxRangeReversals" id="MaxRangeReversals">MaxRangeReversals</a> <a name="maxrangereversals" id="maxrangereversals">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of range reversals (eg: <code>100-200,50-70</code>) allowed before returning the complete
        resource </td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRangeReversals default | unlimited | none | <var>number-of-ranges</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxRangeReversals 20</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.3.15 and later</td></tr>
</table>
        <p>The <code class="directive">MaxRangeReversals</code> directive
            limits the number of HTTP Range reversals the server is willing to
            return to the client. If more ranges reversals than permitted are requested,
            the complete resource is returned instead.</p>

        <dl>
            <dt><strong>default</strong></dt>
            <dd>Limits the number of range reversals to a compile-time default of 20.</dd>

            <dt><strong>none</strong></dt>
            <dd>No Range reversals headers are allowed.</dd>

            <dt><strong>unlimited</strong></dt>
            <dd>The server does not limit the number of range reversals it is
                willing to satisfy.</dd>

            <dt><var>number-of-ranges</var></dt>
            <dd>A positive number representing the maximum number of range reversals the
                server is willing to satisfy.</dd>
        </dl>
    
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="MaxRanges" id="MaxRanges">MaxRanges</a> <a name="maxranges" id="maxranges">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of ranges allowed before returning the complete
resource </td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRanges default | unlimited | none | <var>number-of-ranges</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxRanges 200</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.3.15 and later</td></tr>
</table>
    <p>The <code class="directive">MaxRanges</code> directive
    limits the number of HTTP ranges the server is willing to
    return to the client. If more ranges than permitted are requested,
    the complete resource is returned instead.</p>

    <dl>
      <dt><strong>default</strong></dt>
      <dd>Limits the number of ranges to a compile-time default of 200.</dd>

      <dt><strong>none</strong></dt>
      <dd>Range headers are ignored.</dd>

      <dt><strong>unlimited</strong></dt>
      <dd>The server does not limit the number of ranges it is
          willing to satisfy.</dd>

      <dt><var>number-of-ranges</var></dt>
      <dd>A positive number representing the maximum number of ranges the
      server is willing to satisfy.</dd>
    </dl>

</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="MergeTrailers" id="MergeTrailers">MergeTrailers</a> <a name="mergetrailers" id="mergetrailers">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determines whether trailers are merged into headers</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MergeTrailers [on|off]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MergeTrailers off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>2.4.11 and later</td></tr>
</table>
    <p>This directive controls whether HTTP trailers are copied into the
    internal representation of HTTP headers. This merging occurs when the
    request body has been completely consumed, long after most header
    processing would have a chance to examine or modify request headers.</p>
    <p>This option is provided for compatibility with releases prior to 2.4.11,
    where trailers were always merged.</p>

</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="Mutex" id="Mutex">Mutex</a> <a name="mutex" id="mutex">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures mutex mechanism and lock file directory for all
or specified mutexes</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Mutex <var>mechanism</var> [default|<var>mutex-name</var>] ... [OmitPID]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Mutex default</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.3.4 and later</td></tr>
</table>
    <p>The <code class="directive">Mutex</code> directive sets the mechanism,
    and optionally the lock file location, that httpd and modules use
    to serialize access to resources.  Specify <code>default</code> as
    the second argument to change the settings for all mutexes; specify
    a mutex name (see table below) as the second argument to override
    defaults only for that mutex.</p>

    <p>The <code class="directive">Mutex</code> directive is typically used in
    the following exceptional situations:</p>

    <ul>
        <li>change the mutex mechanism when the default mechanism selected
        by <a class="glossarylink" href="../glossary.html#apr" title="see glossary">APR</a> has a functional or performance
        problem</li>

        <li>change the directory used by file-based mutexes when the
        default directory does not support locking</li>
    </ul>

    <div class="note"><h3>Supported modules</h3>
    <p>This directive only configures mutexes which have been registered
    with the core server using the <code>ap_mutex_register()</code> API.
    All modules bundled with httpd support the <code class="directive">Mutex</code>
    directive, but third-party modules may not.  Consult the documentation
    of the third-party module, which must indicate the mutex name(s) which
    can be configured if this directive is supported.</p>
    </div>

    <p>The following mutex <em>mechanisms</em> are available:</p>
    <ul>
        <li><code>default | yes</code>
        <p>This selects the default locking implementation, as determined by
        <a class="glossarylink" href="../glossary.html#apr" title="see glossary">APR</a>.  The default locking implementation can
        be displayed by running <code class="program"><a href="../programs/httpd.html">httpd</a></code> with the
        <code>-V</code> option.</p></li>

        <li><code>none | no</code>
        <p>This effectively disables the mutex, and is only allowed for a
        mutex if the module indicates that it is a valid choice.  Consult the
        module documentation for more information.</p></li>

        <li><code>posixsem</code>
        <p>This is a mutex variant based on a Posix semaphore.</p>

        <div class="warning"><h3>Warning</h3>
        <p>The semaphore ownership is not recovered if a thread in the process
        holding the mutex segfaults, resulting in a hang of the web server.</p>
        </div>
        </li>

        <li><code>sysvsem</code>
        <p>This is a mutex variant based on a SystemV IPC semaphore.</p>

        <div class="warning"><h3>Warning</h3>
        <p>It is possible to "leak" SysV semaphores if processes crash
        before the semaphore is removed.</p>
	</div>

        <div class="warning"><h3>Security</h3>
        <p>The semaphore API allows for a denial of service attack by any
        CGIs running under the same uid as the webserver (<em>i.e.</em>,
        all CGIs, unless you use something like <code class="program"><a href="../programs/suexec.html">suexec</a></code>
        or <code>cgiwrapper</code>).</p>
	</div>
        </li>

        <li><code>sem</code>
        <p>This selects the "best" available semaphore implementation, choosing
        between Posix and SystemV IPC semaphores, in that order.</p></li>

        <li><code>pthread</code>
        <p>This is a mutex variant based on cross-process Posix thread
        mutexes.</p>

        <div class="warning"><h3>Warning</h3>
        <p>On most systems, if a child process terminates abnormally while
        holding a mutex that uses this implementation, the server will deadlock
        and stop responding to requests.  When this occurs, the server will
        require a manual restart to recover.</p>
        <p>Solaris and Linux are notable exceptions as they provide a mechanism which
        usually allows the mutex to be recovered after a child process
        terminates abnormally while holding a mutex.</p>
        <p>If your system is POSIX compliant or if it implements the
        <code>pthread_mutexattr_setrobust_np()</code> function, you may be able
        to use the <code>pthread</code> option safely.</p>
        </div>
        </li>

        <li><code>fcntl:/path/to/mutex</code>
        <p>This is a mutex variant where a physical (lock-)file and the
        <code>fcntl()</code> function are used as the mutex.</p>

        <div class="warning"><h3>Warning</h3>
        <p>When multiple mutexes based on this mechanism are used within
        multi-threaded, multi-process environments, deadlock errors (EDEADLK)
        can be reported for valid mutex operations if <code>fcntl()</code>
        is not thread-aware, such as on Solaris.</p>
	</div>
        </li>

        <li><code>flock:/path/to/mutex</code>
        <p>This is similar to the <code>fcntl:/path/to/mutex</code> method
        with the exception that the <code>flock()</code> function is used to
        provide file locking.</p></li>

        <li><code>file:/path/to/mutex</code>
        <p>This selects the "best" available file locking implementation,
        choosing between <code>fcntl</code> and <code>flock</code>, in that
        order.</p></li>
    </ul>

    <p>Most mechanisms are only available on selected platforms, where the
    underlying platform and <a class="glossarylink" href="../glossary.html#apr" title="see glossary">APR</a> support it.  Mechanisms
    which aren't available on all platforms are <em>posixsem</em>,
    <em>sysvsem</em>, <em>sem</em>, <em>pthread</em>, <em>fcntl</em>,
    <em>flock</em>, and <em>file</em>.</p>

    <p>With the file-based mechanisms <em>fcntl</em> and <em>flock</em>,
    the path, if provided, is a directory where the lock file will be created.
    The default directory is httpd's run-time file directory relative to
    <code class="directive"><a href="#serverroot">ServerRoot</a></code>.  Always use a local disk
    filesystem for <code>/path/to/mutex</code> and never a directory residing
    on a NFS- or AFS-filesystem.  The basename of the file will be the mutex
    type, an optional instance string provided by the module, and unless the
    <code>OmitPID</code> keyword is specified, the process id of the httpd
    parent process will be appended to make the file name unique, avoiding
    conflicts when multiple httpd instances share a lock file directory.  For
    example, if the mutex name is <code>mpm-accept</code> and the lock file
    directory is <code>/var/httpd/locks</code>, the lock file name for the
    httpd instance with parent process id 12345 would be
    <code>/var/httpd/locks/mpm-accept.12345</code>.</p>

    <div class="warning"><h3>Security</h3>
    <p>It is best to <em>avoid</em> putting mutex files in a world-writable
    directory such as <code>/var/tmp</code> because someone could create
    a denial of service attack and prevent the server from starting by
    creating a lockfile with the same name as the one the server will try
    to create.</p>
    </div>

    <p>The following table documents the names of mutexes used by httpd
    and bundled modules.</p>

    <table class="bordered"><tr class="header">
            <th>Mutex name</th>
            <th>Module(s)</th>
            <th>Protected resource</th>
	</tr>
<tr>
            <td><code>mpm-accept</code></td>
            <td><code class="module"><a href="../mod/prefork.html">prefork</a></code> and <code class="module"><a href="../mod/worker.html">worker</a></code> MPMs</td>
            <td>incoming connections, to avoid the thundering herd problem;
            for more information, refer to the
            <a href="../misc/perf-tuning.html">performance tuning</a>
            documentation</td>
	</tr>
<tr class="odd">
            <td><code>authdigest-client</code></td>
            <td><code class="module"><a href="../mod/mod_auth_digest.html">mod_auth_digest</a></code></td>
            <td>client list in shared memory</td>
	</tr>
<tr>
            <td><code>authdigest-opaque</code></td>
            <td><code class="module"><a href="../mod/mod_auth_digest.html">mod_auth_digest</a></code></td>
            <td>counter in shared memory</td>
	</tr>
<tr class="odd">
            <td><code>ldap-cache</code></td>
            <td><code class="module"><a href="../mod/mod_ldap.html">mod_ldap</a></code></td>
            <td>LDAP result cache</td>
	</tr>
<tr>
            <td><code>rewrite-map</code></td>
            <td><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code></td>
            <td>communication with external mapping programs, to avoid
            intermixed I/O from multiple requests</td>
	</tr>
<tr class="odd">
            <td><code>ssl-cache</code></td>
            <td><code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code></td>
            <td>SSL session cache</td>
	</tr>
<tr>
            <td><code>ssl-stapling</code></td>
            <td><code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code></td>
            <td>OCSP stapling response cache</td>
	</tr>
<tr class="odd">
            <td><code>watchdog-callback</code></td>
            <td><code class="module"><a href="../mod/mod_watchdog.html">mod_watchdog</a></code></td>
            <td>callback function of a particular client module</td>
	</tr>
</table>

    <p>The <code>OmitPID</code> keyword suppresses the addition of the httpd
    parent process id from the lock file name.</p>

    <p>In the following example, the mutex mechanism for the MPM accept
    mutex will be changed from the compiled-in default to <code>fcntl</code>,
    with the associated lock file created in directory
    <code>/var/httpd/locks</code>.  The mutex mechanism for all other mutexes
    will be changed from the compiled-in default to <code>sysvsem</code>.</p>

    <pre class="prettyprint lang-config">Mutex sysvsem default
Mutex fcntl:/var/httpd/locks mpm-accept</pre>


</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="NameVirtualHost" id="NameVirtualHost">NameVirtualHost</a> <a name="namevirtualhost" id="namevirtualhost">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>DEPRECATED: Designates an IP address for name-virtual
hosting</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>NameVirtualHost <var>addr</var>[:<var>port</var>]</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
</table>

<p>Prior to 2.3.11, <code class="directive">NameVirtualHost</code> was required
to instruct the server that a particular IP address and port combination
was usable as a name-based virtual host.  In 2.3.11 and later,
any time an IP address and port combination is used in multiple virtual
hosts, name-based virtual hosting is automatically enabled for that address.</p>

<p>This directive currently has no effect.</p>

<h3>See also</h3>
<ul>
<li><a href="../vhosts/">Virtual Hosts
documentation</a></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="Options" id="Options">Options</a> <a name="options" id="options">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configures what features are available in a particular
directory</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Options
    [+|-]<var>option</var> [[+|-]<var>option</var>] ...</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Options FollowSymlinks</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Options</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The default was changed from All to FollowSymlinks in 2.3.11</td></tr>
</table>
    <p>The <code class="directive">Options</code> directive controls which
    server features are available in a particular directory.</p>

    <p><var>option</var> can be set to <code>None</code>, in which
    case none of the extra features are enabled, or one or more of
    the following:</p>

    <dl>
      <dt><code>All</code></dt>

      <dd>All options except for <code>MultiViews</code>.</dd>

      <dt><code>ExecCGI</code></dt>

      <dd>
      Execution of CGI scripts using <code class="module"><a href="../mod/mod_cgi.html">mod_cgi</a></code>
      is permitted.</dd>

      <dt><code>FollowSymLinks</code></dt>

      <dd>
      The server will follow symbolic links in this directory. This is
      the default setting.
      <div class="note">
      <p>Even though the server follows the symlink it does <em>not</em>
      change the pathname used to match against <code class="directive"><a href="#directory">&lt;Directory&gt;</a></code> sections.</p>

      <p>The <code>FollowSymLinks</code> and
      <code>SymLinksIfOwnerMatch</code> <code class="directive"><a href="#options">Options</a></code> work only in <code class="directive"><a href="#directory">&lt;Directory&gt;</a></code> sections or
      <code>.htaccess</code> files.</p>

      <p>Omitting this option should not be considered a security restriction,
      since symlink testing is subject to race conditions that make it
      circumventable.</p>
      </div></dd>

      <dt><code>Includes</code></dt>

      <dd>
      Server-side includes provided by <code class="module"><a href="../mod/mod_include.html">mod_include</a></code>
      are permitted.</dd>

      <dt><code>IncludesNOEXEC</code></dt>

      <dd>

      Server-side includes are permitted, but the <code>#exec
      cmd</code> and <code>#exec cgi</code> are disabled. It is still
      possible to <code>#include virtual</code> CGI scripts from
      <code class="directive"><a href="../mod/mod_alias.html#scriptalias">ScriptAlias</a></code>ed
      directories.</dd>

      <dt><code>Indexes</code></dt>

      <dd>
      If a URL which maps to a directory is requested and there
      is no <code class="directive"><a href="../mod/mod_dir.html#directoryindex">DirectoryIndex</a></code>
      (<em>e.g.</em>, <code>index.html</code>) in that directory, then
      <code class="module"><a href="../mod/mod_autoindex.html">mod_autoindex</a></code> will return a formatted listing
      of the directory.</dd>

      <dt><code>MultiViews</code></dt>

      <dd>
      <a href="../content-negotiation.html">Content negotiated</a>
      "MultiViews" are allowed using
      <code class="module"><a href="../mod/mod_negotiation.html">mod_negotiation</a></code>.
      <div class="note"><h3>Note</h3> <p>This option gets ignored if set
      anywhere other than <code class="directive"><a href="#directory">&lt;Directory&gt;</a></code>, as <code class="module"><a href="../mod/mod_negotiation.html">mod_negotiation</a></code>
      needs real resources to compare against and evaluate from.</p></div>
      </dd>

      <dt><code>SymLinksIfOwnerMatch</code></dt>

      <dd>The server will only follow symbolic links for which the
      target file or directory is owned by the same user id as the
      link.

      <div class="note"><h3>Note</h3>
      <p>The <code>FollowSymLinks</code> and
      <code>SymLinksIfOwnerMatch</code> <code class="directive"><a href="#options">Options</a></code> work only in <code class="directive"><a href="#directory">&lt;Directory&gt;</a></code> sections or
      <code>.htaccess</code> files.</p>

      <p>This option should not be considered a security restriction,
      since symlink testing is subject to race conditions that make it
      circumventable.</p>
      </div> </dd>
    </dl>

    <p>Normally, if multiple <code class="directive">Options</code> could
    apply to a directory, then the most specific one is used and
    others are ignored; the options are not merged. (See <a href="../sections.html#merging">how sections are merged</a>.)
    However if <em>all</em> the options on the
    <code class="directive">Options</code> directive are preceded by a
    <code>+</code> or <code>-</code> symbol, the options are
    merged. Any options preceded by a <code>+</code> are added to the
    options currently in force, and any options preceded by a
    <code>-</code> are removed from the options currently in
    force. </p>

    <div class="note"><h3>Note</h3>
    <p>Mixing <code class="directive">Options</code> with a <code>+</code> or
    <code>-</code> with those without is not valid syntax and will be
    rejected during server startup by the syntax check with an abort.</p>
    </div>

    <p>For example, without any <code>+</code> and <code>-</code> symbols:</p>

    <pre class="prettyprint lang-config">&lt;Directory "/web/docs"&gt;
  Options Indexes FollowSymLinks
&lt;/Directory&gt;

&lt;Directory "/web/docs/spec"&gt;
  Options Includes
&lt;/Directory&gt;</pre>


    <p>then only <code>Includes</code> will be set for the
    <code>/web/docs/spec</code> directory. However if the second
    <code class="directive">Options</code> directive uses the <code>+</code> and
    <code>-</code> symbols:</p>

    <pre class="prettyprint lang-config">&lt;Directory "/web/docs"&gt;
  Options Indexes FollowSymLinks
&lt;/Directory&gt;

&lt;Directory "/web/docs/spec"&gt;
  Options +Includes -Indexes
&lt;/Directory&gt;</pre>


    <p>then the options <code>FollowSymLinks</code> and
    <code>Includes</code> are set for the <code>/web/docs/spec</code>
    directory.</p>

    <div class="note"><h3>Note</h3>
      <p>Using <code>-IncludesNOEXEC</code> or
      <code>-Includes</code> disables server-side includes completely
      regardless of the previous setting.</p>
    </div>

    <p>The default in the absence of any other settings is
    <code>FollowSymlinks</code>.</p>

</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="Protocol" id="Protocol">Protocol</a> <a name="protocol" id="protocol">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Protocol for a listening socket</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Protocol <var>protocol</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.1.5 and later.
On Windows, from Apache 2.3.3 and later.</td></tr>
</table>
    <p>This directive specifies the protocol used for a specific listening socket.
       The protocol is used to determine which module should handle a request and
       to apply protocol specific optimizations with the <code class="directive">AcceptFilter</code>
       directive.</p>

    <p>You only need to set the protocol if you are running on non-standard ports;
       otherwise, <code>http</code> is assumed for port 80 and <code>https</code>
       for port 443.</p>

    <p>For example, if you are running <code>https</code> on a non-standard port,
       specify the protocol explicitly:</p>

    <pre class="prettyprint lang-config">Protocol https</pre>


    <p>You can also specify the protocol using the <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code> directive.</p>

<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#acceptfilter">AcceptFilter</a></code></li>
<li><code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="Protocols" id="Protocols">Protocols</a> <a name="protocols" id="protocols">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Protocols available for a server/virtual host</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Protocols <var>protocol</var> ...</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Protocols http/1.1</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only available from Apache 2.4.17 and later.</td></tr>
</table>
        <p>This directive specifies the list of protocols supported for a
            server/virtual host. The list determines the allowed protocols
            a client may negotiate for this server/host.</p>
        
        <p>You need to set protocols if you want to extend the available
            protocols for a server/host. By default, only the http/1.1 protocol
            (which includes the compatibility with 1.0 and 0.9 clients) is
            allowed.</p>
        
        <p>For example, if you want to support HTTP/2 for a server with TLS, 
            specify:</p>
        
        <pre class="prettyprint lang-config">Protocols h2 http/1.1</pre>


        <p>Valid protocols are <code>http/1.1</code> for http and https connections,
            <code>h2</code> on https connections and <code>h2c</code> for http
            connections. Modules may enable more protocols.</p>
        
        <p>It is safe to specify protocols that are unavailable/disabled. Such
        protocol names will simply be ignored.</p>
        
        <p>Protocols specified in base servers are inherited for virtual hosts 
            only if the virtual host has no own Protocols directive. Or, the other
            way around, Protocols directives in virtual hosts replace any
            such directive in the base server.
        </p>

    
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#protocolshonororder">ProtocolsHonorOrder</a></code></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ProtocolsHonorOrder" id="ProtocolsHonorOrder">ProtocolsHonorOrder</a> <a name="protocolshonororder" id="protocolshonororder">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Determines if order of Protocols determines precedence during negotiation</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProtocolsHonorOrder On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ProtocolsHonorOrder On</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only available from Apache 2.4.17 and later.</td></tr>
</table>
        <p>This directive specifies if the server should honor the order in which
        the <code class="directive">Protocols</code> directive lists protocols.</p>
        
        <p>If configured Off, the client supplied list order of protocols has 
            precedence over the order in the server configuration.</p>
        
        <p>With <code class="directive">ProtocolsHonorOrder</code> set to <code>on</code> 
            (default), the client ordering does not matter and only the ordering 
            in the server settings influences the outcome of the protocol 
            negotiation.</p>
        
    
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#protocols">Protocols</a></code></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="QualifyRedirectURL" id="QualifyRedirectURL">QualifyRedirectURL</a> <a name="qualifyredirecturl" id="qualifyredirecturl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Controls whether the REDIRECT_URL environment variable is
             fully qualified</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>QualifyRedirectURL ON|OFF</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>QualifyRedirectURL OFF</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Directive supported in 2.4.18 and later. 2.4.17 acted
as if 'QualifyRedirectURL ON' was configured.</td></tr>
</table>
    <p>This directive controls whether the server will ensure that the 
    REDIRECT_URL environment variable is fully qualified.  By default, 
    the variable contains the verbatim URL requested by the client, 
    such as "/index.html".  With <code class="directive"><a href="#qualifyredirecturl on">QualifyRedirectURL ON</a></code>, the same request would result in a
    value such as "http://www.example.com/index.html".</p>
    <p>Even without this directive set, when a request is issued against a 
    fully qualified URL, REDIRECT_URL will remain fully qualified.
    </p>

</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RegisterHttpMethod" id="RegisterHttpMethod">RegisterHttpMethod</a> <a name="registerhttpmethod" id="registerhttpmethod">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Register non-standard HTTP methods</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RegisterHttpMethod <var>method</var> [<var>method</var> [...]]</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
</table>
<p>HTTP Methods that are not conforming to the relevant RFCs are normally
rejected by request processing in Apache HTTPD. To avoid this, modules
can register non-standard HTTP methods they support.
The <code class="directive">RegisterHttpMethod</code> allows to register such
methods manually. This can be useful for if such methods are forwared
for external processing, e.g. to a CGI script.</p>

</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RLimitCPU" id="RLimitCPU">RLimitCPU</a> <a name="rlimitcpu" id="rlimitcpu">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the CPU consumption of processes launched
by Apache httpd children</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitCPU <var>seconds</var>|max [<var>seconds</var>|max]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
</table>
    <p>Takes 1 or 2 parameters. The first parameter sets the soft
    resource limit for all processes and the second parameter sets
    the maximum resource limit. Either parameter can be a number,
    or <code>max</code> to indicate to the server that the limit should
    be set to the maximum allowed by the operating system
    configuration. Raising the maximum resource limit requires that
    the server is running as <code>root</code> or in the initial startup
    phase.</p>

    <p>This applies to processes forked from Apache httpd children
    servicing requests, not the Apache httpd children themselves. This
    includes CGI scripts and SSI exec commands, but not any
    processes forked from the Apache httpd parent, such as piped
    logs.</p>

    <p>CPU resource limits are expressed in seconds per
    process.</p>

<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#rlimitmem">RLimitMEM</a></code></li>
<li><code class="directive"><a href="#rlimitnproc">RLimitNPROC</a></code></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RLimitMEM" id="RLimitMEM">RLimitMEM</a> <a name="rlimitmem" id="rlimitmem">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the memory consumption of processes launched
by Apache httpd children</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitMEM <var>bytes</var>|max [<var>bytes</var>|max]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
</table>
    <p>Takes 1 or 2 parameters. The first parameter sets the soft
    resource limit for all processes and the second parameter sets
    the maximum resource limit. Either parameter can be a number,
    or <code>max</code> to indicate to the server that the limit should
    be set to the maximum allowed by the operating system
    configuration. Raising the maximum resource limit requires that
    the server is running as <code>root</code> or in the initial startup
    phase.</p>

    <p>This applies to processes forked from Apache httpd children
    servicing requests, not the Apache httpd children themselves. This
    includes CGI scripts and SSI exec commands, but not any
    processes forked from the Apache httpd parent, such as piped
    logs.</p>

    <p>Memory resource limits are expressed in bytes per
    process.</p>

<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#rlimitcpu">RLimitCPU</a></code></li>
<li><code class="directive"><a href="#rlimitnproc">RLimitNPROC</a></code></li>
</ul>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RLimitNPROC" id="RLimitNPROC">RLimitNPROC</a> <a name="rlimitnproc" id="rlimitnproc">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limits the number of processes that can be launched by
processes launched by Apache httpd children</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RLimitNPROC <var>number</var>|max [<var>number</var>|max]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset; uses operating system defaults</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>All</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Core</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>core</td></tr>
</table>
    <p>Takes 1 or 2 parameters. The first parameter sets the soft
    resource limit for all processes, and the second parameter sets
    the maximum resource limit. Either parameter can be a number,
    or <code>max</code> to indicate to the server that the limit
    should be set to the maximum allowed by the operating system
    configuration. Raising the maximum resource limit requires that
    the server is running as <code>root</code> or in the initial startup
    phase.</p>

    <p>This applies to processes forked from Apache httpd children
    servicing requests, not the Apache httpd children themselves. This
    includes CGI scripts and SSI exec commands, but not any
    processes forked from the Apache httpd parent, such as piped
    logs.</p>

    <p>Process limits control the number of processes per user.</p>

    <div class="note"><h3>Note</h3>
      <p>If CGI processes are <strong>not</strong> running
      under user ids other than the web server user id, this directive
      will limit the number of processes that the server itself can
      create. Evidence of this situation will be indicated by
      <strong><code>cannot fork</code></strong> messages in the
      <code>error_log</code>.</p>
    </div>