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authorhongbotian <hongbo.tianhongbo@huawei.com>2015-11-30 01:45:08 -0500
committerhongbotian <hongbo.tianhongbo@huawei.com>2015-11-30 01:45:08 -0500
commite8ec7aa8e38a93f5b034ac74cebce5de23710317 (patch)
treeaa031937bf856c1f8d6ad7877b8d2cb0224da5ef /rubbos/app/httpd-2.0.64/docs/manual/mod/mpm_common.html.en
parentcc40af334e619bb549038238507407866f774f8f (diff)
upload http
JIRA: BOTTLENECK-10 Change-Id: I7598427ff904df438ce77c2819ee48ac75ffa8da Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
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+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>mpm_common - Apache HTTP Server</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
+<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
+<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
+<link href="../images/favicon.ico" rel="shortcut icon" /></head>
+<body>
+<div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.0</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.0</a> &gt; <a href="./">Modules</a></div>
+<div id="page-content">
+<div id="preamble"><h1>Apache MPM Common Directives</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
+<a href="../en/mod/mpm_common.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../es/mod/mpm_common.html" hreflang="es" rel="alternate" title="Español">&nbsp;es&nbsp;</a> |
+<a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
+</div>
+<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A collection of directives that are implemented by
+more than one multi-processing module (MPM)</td></tr>
+<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr></table>
+</div>
+<div id="quickview"><h3 class="directives">Directives</h3>
+<ul id="toc">
+<li><img alt="" src="../images/down.gif" /> <a href="#acceptmutex">AcceptMutex</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#bs2000account">BS2000Account</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#coredumpdirectory">CoreDumpDirectory</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#enableexceptionhook">EnableExceptionHook</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#group">Group</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#listen">Listen</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#listenbacklog">ListenBackLog</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#lockfile">LockFile</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#maxclients">MaxClients</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#maxmemfree">MaxMemFree</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#maxrequestsperchild">MaxRequestsPerChild</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#maxsparethreads">MaxSpareThreads</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#minsparethreads">MinSpareThreads</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#pidfile">PidFile</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#receivebuffersize">ReceiveBufferSize</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#scoreboardfile">ScoreBoardFile</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#sendbuffersize">SendBufferSize</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#serverlimit">ServerLimit</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#startservers">StartServers</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#startthreads">StartThreads</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#threadlimit">ThreadLimit</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#threadsperchild">ThreadsPerChild</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#user">User</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="AcceptMutex" id="AcceptMutex">AcceptMutex</a> <a name="acceptmutex" id="acceptmutex">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Method that Apache uses to serialize multiple children
+accepting requests on network sockets</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AcceptMutex Default|<var>method</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AcceptMutex 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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The <code class="directive">AcceptMutex</code> directives sets the
+ method that Apache uses to serialize multiple children accepting
+ requests on network sockets. Prior to Apache 2.0, the method was
+ selectable only at compile time. The optimal method to use is
+ highly architecture and platform dependent. For further details,
+ see the <a href="../misc/perf-tuning.html">performance tuning</a>
+ documentation.</p>
+
+ <p>If this directive is set to <code>Default</code>, then the
+ compile-time selected default will be used. Other possible
+ methods are listed below. Note that not all methods are
+ available on all platforms. If a method is specified which is
+ not available, a message will be written to the error log
+ listing the available methods.</p>
+
+ <dl>
+ <dt><code>flock</code></dt>
+ <dd>uses the <code>flock(2)</code> system call to lock the
+ file defined by the <code class="directive"><a href="#lockfile">LockFile</a></code> directive.</dd>
+
+ <dt><code>fcntl</code></dt>
+ <dd>uses the <code>fcntl(2)</code> system call to lock the
+ file defined by the <code class="directive"><a href="#lockfile">LockFile</a></code> directive.</dd>
+
+ <dt><code>posixsem</code></dt>
+ <dd>uses POSIX compatible semaphores to implement the mutex.</dd>
+
+ <dt><code>pthread</code></dt>
+ <dd>uses POSIX mutexes as implemented by the POSIX Threads
+ (PThreads) specification.</dd>
+
+ <dt><code>sysvsem</code></dt>
+ <dd>uses SySV-style semaphores to implement the mutex.</dd>
+ </dl>
+
+ <p>If you want to find out the compile time chosen default
+ for your system, you may set your <code class="directive"><a href="../mod/core.html#loglevel">LogLevel</a></code> to <code>debug</code>. Then the default <code class="directive">AcceptMutex</code> will be written into the <code class="directive"><a href="../mod/core.html#errorlog">ErrorLog</a></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="BS2000Account" id="BS2000Account">BS2000Account</a> <a name="bs2000account" id="bs2000account">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Define the non-privileged account on BS2000
+machines</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BS2000Account <var>account</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only available for BS2000 machines</td></tr>
+</table>
+ <p>The <code class="directive">BS2000Account</code> directive is available for
+ BS2000 hosts only. It must be used to define the account number for
+ the non-privileged apache server user (which was configured using the
+ <code class="directive"><a href="#user">User</a></code> directive). This is
+ required by the BS2000 POSIX subsystem (to change the underlying BS2000
+ task environment by performing a sub-LOGON) to prevent CGI scripts
+ from accessing resources of the privileged account which started the
+ server, usually <code>SYSROOT</code>.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>Only one <code>BS2000Account</code> directive can be used.</p>
+ </div>
+
+<h3>See also</h3>
+<ul>
+<li><a href="../platform/ebcdic.html">Apache EBCDIC port</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="CoreDumpDirectory" id="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory" id="coredumpdirectory">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory where Apache attempts to
+switch before dumping core</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CoreDumpDirectory <var>directory</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for the default setting</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>This controls the directory to which Apache attempts to
+ switch before dumping core. The default is in the
+ <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code> directory, however
+ since this should not be writable by the user the server runs
+ as, core dumps won't normally get written. If you want a core
+ dump for debugging, you can use this directive to place it in a
+ different location.</p>
+
+ <div class="note"><h3>Core Dumps on Linux</h3>
+ <p>If Apache starts as root and switches to another user, the
+ Linux kernel <em>disables</em> core dumps even if the directory is
+ writable for the process. Apache (2.0.46 and later) reenables core dumps
+ on Linux 2.4 and beyond, but only if you explicitly configure a <code class="directive">CoreDumpDirectory</code>.</p>
+ </div>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="EnableExceptionHook" id="EnableExceptionHook">EnableExceptionHook</a> <a name="enableexceptionhook" id="enableexceptionhook">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a hook that runs exception handlers
+after a crash</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableExceptionHook On|Off</code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableExceptionHook Off</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.49 and later</td></tr>
+</table>
+ <p>For safety reasons this directive is only available if the server was
+ configured with the <code>--enable-exception-hook</code> option. It
+ enables a hook that allows external modules to plug in and do something
+ after a child crashed.</p>
+
+ <p>There are already two modules, <code>mod_whatkilledus</code> and
+ <code>mod_backtrace</code> that make use of this hook. Please have a
+ look at Jeff Trawick's <a href="http://www.apache.org/~trawick/exception_hook.html">EnableExceptionHook site</a> for more information about these.</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="Group" id="Group">Group</a> <a name="group" id="group">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Group under which the server will answer
+requests</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Group <var>unix-group</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Group #-1</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only valid in global server config since Apache
+2.0</td></tr>
+</table>
+ <p>The <code class="directive">Group</code> directive sets the group under
+ which the server will answer requests. In order to use this
+ directive, the server must be run initially as <code>root</code>. If
+ you start the server as a non-root user, it will fail to change to the
+ specified group, and will instead continue to run as the group of the
+ original user. <var>Unix-group</var> is one of:</p>
+
+ <dl>
+ <dt>A group name</dt>
+ <dd>Refers to the given group by name.</dd>
+
+ <dt><code>#</code> followed by a group number.</dt>
+ <dd>Refers to a group by its number.</dd>
+ </dl>
+
+ <div class="example"><h3>Example</h3><p><code>
+ Group www-group
+ </code></p></div>
+
+ <p>It is recommended that you set up a new group specifically for
+ running the server. Some admins use user <code>nobody</code>,
+ but this is not always possible or desirable.</p>
+
+ <div class="warning"><h3>Security</h3>
+ <p>Don't set <code class="directive">Group</code> (or <code class="directive"><a href="#user">User</a></code>) to <code>root</code> unless
+ you know exactly what you are doing, and what the dangers are.</p>
+ </div>
+
+ <p>Special note: Use of this directive in <code class="directive"><a href="../mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code> is no longer supported. To
+ configure your server for <code class="program"><a href="../programs/suexec.html">suexec</a></code> use
+ <code class="directive"><a href="../mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>Although the <code class="directive">Group</code> directive is present
+ in the <code class="module"><a href="../mod/beos.html">beos</a></code> and <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> MPMs,
+ it is actually a no-op there and only exists for compatibility
+ reasons.</p>
+ </div>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="Listen" id="Listen">Listen</a> <a name="listen" id="listen">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>IP addresses and ports that the server
+listens to</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Listen [<var>IP-address</var>:]<var>portnumber</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Required directive since Apache 2.0</td></tr>
+</table>
+ <p>The <code class="directive">Listen</code> directive instructs Apache to
+ listen to only specific IP addresses or ports; by default it
+ responds to requests on all IP interfaces. <code class="directive">Listen</code>
+ is now a required directive. If it is not in the config file, the
+ server will fail to start. This is a change from previous versions
+ of Apache.</p>
+
+ <p>The <code class="directive">Listen</code> directive tells the server to
+ accept incoming requests on the specified port or address-and-port
+ combination. If only a port number is specified, the server listens to
+ the given port on all interfaces. If an IP address is given as well
+ as a port, the server will listen on the given port and
+ interface.</p>
+
+ <p>Multiple <code class="directive">Listen</code> directives may be used to
+ specify a number of addresses and ports to listen to. The server will
+ respond to requests from any of the listed addresses and ports.</p>
+
+ <p>For example, to make the server accept connections on both
+ port 80 and port 8000, use:</p>
+
+ <div class="example"><p><code>
+ Listen 80<br />
+ Listen 8000
+ </code></p></div>
+
+ <p>To make the server accept connections on two specified
+ interfaces and port numbers, use </p>
+
+ <div class="example"><p><code>
+ Listen 192.170.2.1:80<br />
+ Listen 192.170.2.5:8000
+ </code></p></div>
+
+ <p>IPv6 addresses must be surrounded in square brackets, as in the
+ following example:</p>
+
+ <div class="example"><p><code>
+ Listen [2001:db8::a00:20ff:fea7:ccea]:80
+ </code></p></div>
+
+ <div class="note"><h3>Error condition</h3>
+ Multiple <code class="directive">Listen</code> directives for the same ip
+ address and port will result in an <code>Address already in use</code>
+ error message.
+ </div>
+
+<h3>See also</h3>
+<ul>
+<li><a href="../dns-caveats.html">DNS Issues</a></li>
+<li><a href="../bind.html">Setting which addresses and ports Apache
+ uses</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="ListenBackLog" id="ListenBackLog">ListenBackLog</a> <a name="listenbacklog" id="listenbacklog">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum length of the queue of pending connections</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenBacklog <var>backlog</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenBacklog 511</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The maximum length of the queue of pending connections.
+ Generally no tuning is needed or desired, however on some
+ systems it is desirable to increase this when under a TCP SYN
+ flood attack. See the backlog parameter to the
+ <code>listen(2)</code> system call.</p>
+
+ <p>This will often be limited to a smaller number by the
+ operating system. This varies from OS to OS. Also note that
+ many OSes do not use exactly what is specified as the backlog,
+ but use a number based on (but normally larger than) what is
+ set.</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="LockFile" id="LockFile">LockFile</a> <a name="lockfile" id="lockfile">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the accept serialization lock file</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LockFile <var>filename</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LockFile logs/accept.lock</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The <code class="directive">LockFile</code> directive sets the path to
+ the lockfile used when Apache is used with an <code class="directive"><a href="#acceptmutex">AcceptMutex</a></code> value of either
+ <code>fcntl</code> or <code>flock</code>. This directive should
+ normally be left at its default value. The main reason for changing
+ it is if the <code>logs</code> directory is NFS mounted, since
+ <strong>the lockfile must be stored on a local disk</strong>. The PID
+ of the main server process is automatically appended to the
+ filename.</p>
+
+ <div class="warning"><h3>Security</h3>
+ <p>It is best to <em>avoid</em> putting this file 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>
+
+<h3>See also</h3>
+<ul>
+<li><code class="directive"><a href="#acceptmutex">AcceptMutex</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="MaxClients" id="MaxClients">MaxClients</a> <a name="maxclients" id="maxclients">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of connections that will be processed
+simultaneously</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxClients <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The <code class="directive">MaxClients</code> directive sets the limit
+ on the number of simultaneous requests that will be served. Any
+ connection attempts over the <code class="directive">MaxClients</code>
+ limit will normally be queued, up to a number based on the
+ <code class="directive"><a href="#listenbacklog">ListenBacklog</a></code>
+ directive. Once a child process is freed at the end of a different
+ request, the connection will then be serviced.</p>
+
+ <p>For non-threaded servers (<em>i.e.</em>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>),
+ <code class="directive">MaxClients</code> translates into the maximum
+ number of child processes that will be launched to serve requests.
+ The default value is <code>256</code>; to increase it, you must also raise
+ <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
+
+ <p>For threaded and hybrid servers (<em>e.g.</em> <code class="module"><a href="../mod/beos.html">beos</a></code>
+ or <code class="module"><a href="../mod/worker.html">worker</a></code>) <code class="directive">MaxClients</code> restricts
+ the total number of threads that will be available to serve clients.
+ The default value for <code class="module"><a href="../mod/beos.html">beos</a></code> is <code>50</code>. For
+ hybrid MPMs the default value is <code>16</code> (<code class="directive"><a href="#serverlimit">ServerLimit</a></code>) multiplied by the value of
+ <code>25</code> (<code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>). Therefore, to increase <code class="directive">MaxClients</code> to a value that requires more than 16 processes,
+ you must also raise <code class="directive"><a href="#serverlimit">ServerLimit</a></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="MaxMemFree" id="MaxMemFree">MaxMemFree</a> <a name="maxmemfree" id="maxmemfree">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of memory that the main allocator is allowed
+to hold without calling <code>free()</code></td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxMemFree <var>KBytes</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxMemFree 0</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code></td></tr>
+</table>
+ <p>The <code class="directive">MaxMemFree</code> directive sets the
+ maximum number of free Kbytes that the main allocator is allowed
+ to hold without calling <code>free()</code>. When not set, or when set
+ to zero, the threshold will be set to unlimited.</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="MaxRequestsPerChild" id="MaxRequestsPerChild">MaxRequestsPerChild</a> <a name="maxrequestsperchild" id="maxrequestsperchild">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on the number of requests that an individual child server
+will handle during its life</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRequestsPerChild <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxRequestsPerChild 10000</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The <code class="directive">MaxRequestsPerChild</code> directive sets
+ the limit on the number of requests that an individual child
+ server process will handle. After
+ <code class="directive">MaxRequestsPerChild</code> requests, the child
+ process will die. If <code class="directive">MaxRequestsPerChild</code> is
+ <code>0</code>, then the process will never expire.</p>
+
+ <div class="note"><h3>Different default values</h3>
+ <p>The default value for <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> and
+ <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> is <code>0</code>.</p>
+ </div>
+
+ <p>Setting <code class="directive">MaxRequestsPerChild</code> to a
+ non-zero value limits the amount of memory that process can consume
+ by (accidental) memory leakage.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>For <code class="directive"><a href="../mod/core.html#keepalive">KeepAlive</a></code> requests, only
+ the first request is counted towards this limit. In effect, it
+ changes the behavior to limit the number of <em>connections</em> per
+ child.</p>
+ </div>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="MaxSpareThreads" id="MaxSpareThreads">MaxSpareThreads</a> <a name="maxsparethreads" id="maxsparethreads">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle threads</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareThreads <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>Maximum number of idle threads. Different MPMs deal with this
+ directive differently.</p>
+
+ <p>For <code class="module"><a href="../mod/perchild.html">perchild</a></code> the default is
+ <code>MaxSpareThreads 10</code>. This MPM monitors the number of
+ idle threads on a per-child basis. If there are too many idle
+ threads in that child, the server will begin to kill threads
+ within that child.</p>
+
+ <p>For <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code> and <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> the default is <code>MaxSpareThreads 250</code>.
+ These MPMs deal with idle threads on a server-wide basis. If there
+ are too many idle threads in the server then child processes are
+ killed until the number of idle threads is less than this number.</p>
+
+ <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
+ <code>MaxSpareThreads 100</code>. Since this MPM runs a
+ single-process, the spare thread count is also server-wide.</p>
+
+ <p><code class="module"><a href="../mod/beos.html">beos</a></code> and <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> work
+ similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. The default for
+ <code class="module"><a href="../mod/beos.html">beos</a></code> is <code>MaxSpareThreads 50</code>. For
+ <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>10</code>.</p>
+
+ <div class="note"><h3>Restrictions</h3>
+ <p>The range of the <code class="directive">MaxSpareThreads</code> value
+ is restricted. Apache will correct the given value automatically
+ according to the following rules:</p>
+ <ul>
+ <li><code class="module"><a href="../mod/perchild.html">perchild</a></code> requires <code class="directive">MaxSpareThreads</code> to be less or equal than <code class="directive"><a href="#threadlimit">ThreadLimit</a></code>.</li>
+
+ <li><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> wants the value to be greater than
+ <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>.</li>
+
+ <li>For <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> and
+ <code class="module"><a href="../mod/worker.html">worker</a></code> the value must be greater or equal than
+ the sum of <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>
+ and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</li>
+ </ul>
+ </div>
+
+<h3>See also</h3>
+<ul>
+<li><code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code></li>
+<li><code class="directive"><a href="#startservers">StartServers</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="MinSpareThreads" id="MinSpareThreads">MinSpareThreads</a> <a name="minsparethreads" id="minsparethreads">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle threads available to handle request
+spikes</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareThreads <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>Minimum number of idle threads to handle request spikes.
+ Different MPMs deal with this directive
+ differently.</p>
+
+ <p><code class="module"><a href="../mod/perchild.html">perchild</a></code> uses a default of
+ <code>MinSpareThreads 5</code> and monitors the number of idle
+ threads on a per-child basis. If there aren't enough idle threads
+ in that child, the server will begin to create new threads within
+ that child. Thus, if you set <code class="directive"><a href="../mod/perchild.html#numservers">NumServers</a></code> to <code>10</code> and a <code class="directive">MinSpareThreads</code> value of <code>5</code>, you'll have
+ at least 50 idle threads on your system.</p>
+
+ <p><code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code> and
+ <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> use a default of <code>MinSpareThreads
+ 75</code> and deal with idle threads on a server-wide basis. If
+ there aren't enough idle threads in the server then child
+ processes are created until the number of idle threads is greater
+ than number.</p>
+
+ <p><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> uses a default of
+ <code>MinSpareThreads 10</code> and, since it is a single-process
+ MPM, tracks this on a server-wide bases.</p>
+
+ <p><code class="module"><a href="../mod/beos.html">beos</a></code> and <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> work
+ similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. The default for
+ <code class="module"><a href="../mod/beos.html">beos</a></code> is <code>MinSpareThreads 1</code>. For
+ <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>5</code>.</p>
+
+<h3>See also</h3>
+<ul>
+<li><code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code></li>
+<li><code class="directive"><a href="#startservers">StartServers</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="PidFile" id="PidFile">PidFile</a> <a name="pidfile" id="pidfile">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File where the server records the process ID
+of the daemon</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PidFile <var>filename</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>PidFile logs/httpd.pid</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The <code class="directive">PidFile</code> directive sets the file to
+ which the server records the process id of the daemon. If the
+ filename is not absolute then it is assumed to be relative to the
+ <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
+
+ <div class="example"><h3>Example</h3><p><code>
+ PidFile /var/run/apache.pid
+ </code></p></div>
+
+ <p>It is often useful to be able to send the server a signal,
+ so that it closes and then re-opens its <code class="directive"><a href="../mod/core.html#errorlog">ErrorLog</a></code> and <code class="directive"><a href="../mod/mod_log_config.html#transferlog">TransferLog</a></code>, and
+ re-reads its configuration files. This is done by sending a
+ SIGHUP (kill -1) signal to the process id listed in the
+ <code class="directive">PidFile</code>.</p>
+
+ <p>The <code class="directive">PidFile</code> is subject to the same
+ warnings about log file placement and <a href="../misc/security_tips.html#serverroot">security</a>.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>As of Apache 2 it is recommended to use only the <code class="program"><a href="../programs/apachectl.html">apachectl</a></code> script for (re-)starting or stopping the server.</p>
+ </div>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ReceiveBufferSize" id="ReceiveBufferSize">ReceiveBufferSize</a> <a name="receivebuffersize" id="receivebuffersize">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP receive buffer size</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ReceiveBufferSize <var>bytes</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ReceiveBufferSize 0</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The server will set the TCP receive buffer size to the number of
+ bytes specified.</p>
+
+ <p>If set to the value of <code>0</code>, the server will use the
+ OS default.</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="ScoreBoardFile" id="ScoreBoardFile">ScoreBoardFile</a> <a name="scoreboardfile" id="scoreboardfile">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the file used to store coordination data for
+the child processes</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScoreBoardFile <var>file-path</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScoreBoardFile logs/apache_status</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>Apache uses a scoreboard to communicate between its parent
+ and child processes. Some architectures require a file to facilitate
+ this communication. If the file is left unspecified, Apache first
+ attempts to create the scoreboard entirely in memory (using anonymous
+ shared memory) and, failing that, will attempt to create the file on
+ disk (using file-based shared memory). Specifying this directive causes
+ Apache to always create the file on the disk.</p>
+
+ <div class="example"><h3>Example</h3><p><code>
+ ScoreBoardFile /var/run/apache_status
+ </code></p></div>
+
+ <p>File-based shared memory is useful for third-party applications
+ that require direct access to the scoreboard.</p>
+
+ <p>If you use a <code class="directive">ScoreBoardFile</code> then
+ you may see improved speed by placing it on a RAM disk. But be
+ careful that you heed the same warnings about log file placement
+ and <a href="../misc/security_tips.html">security</a>.</p>
+
+<h3>See also</h3>
+<ul>
+<li><a href="../stopping.html">Stopping and Restarting
+Apache</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="SendBufferSize" id="SendBufferSize">SendBufferSize</a> <a name="sendbuffersize" id="sendbuffersize">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP buffer size</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SendBufferSize <var>bytes</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SendBufferSize 0</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The server will set the TCP send buffer size to the number of bytes
+ specified. Very useful to increase past standard OS defaults on
+ high speed high latency (<em>i.e.</em>, 100ms or so, such as
+ transcontinental fast pipes).</p>
+
+ <p>If set to the value of <code>0</code>, the server will use the
+ OS default.</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="ServerLimit" id="ServerLimit">ServerLimit</a> <a name="serverlimit" id="serverlimit">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Upper limit on configurable number of processes</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerLimit <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>For the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, this directive sets the
+ maximum configured value for <code class="directive"><a href="#maxclients">MaxClients</a></code> for the lifetime of the
+ Apache process. For the <code class="module"><a href="../mod/worker.html">worker</a></code> MPM, this directive
+ in combination with <code class="directive"><a href="#threadlimit">ThreadLimit</a></code> sets
+ the maximum configured value for <code class="directive"><a href="#maxclients">MaxClients</a></code> for the lifetime of the
+ Apache process. Any attempts to change this directive during a
+ restart will be ignored, but <code class="directive"><a href="#maxclients">MaxClients</a></code> can be modified during
+ a restart.</p>
+
+ <p>Special care must be taken when using this directive. If
+ <code class="directive">ServerLimit</code> is set to a value much higher
+ than necessary, extra, unused shared memory will be allocated. If
+ both <code class="directive">ServerLimit</code> and <code class="directive"><a href="#maxclients">MaxClients</a></code> are set to values
+ higher than the system can handle, Apache may not start or the
+ system may become unstable.</p>
+
+ <p>With the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, use this directive only
+ if you need to set <code class="directive"><a href="#maxclients">MaxClients</a></code> higher than 256 (default).
+ Do not set the value of this directive any higher than what you
+ might want to set <code class="directive"><a href="#maxclients">MaxClients</a></code> to.</p>
+
+ <p>With <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code> and
+ <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> use this directive only
+ if your <code class="directive"><a href="#maxclients">MaxClients</a></code> and
+ <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>
+ settings require more than 16 server processes (default). Do not set
+ the value of this directive any higher than the number of server
+ processes required by what you may want for <code class="directive"><a href="#maxclients ">MaxClients </a></code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</p>
+
+ <p>With the <code class="module"><a href="../mod/perchild.html">perchild</a></code> MPM, use this directive only
+ if you need to set <code class="directive"><a href="../mod/perchild.html#numservers">NumServers</a></code> higher than 8 (default).</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>There is a hard limit of <code>ServerLimit 20000</code> compiled
+ into the server. This is intended to avoid nasty effects caused by
+ typos.</p>
+ </div>
+
+<h3>See also</h3>
+<ul>
+<li><a href="../stopping.html">Stopping and Restarting Apache</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="StartServers" id="StartServers">StartServers</a> <a name="startservers" id="startservers">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of child server processes created at startup</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartServers <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>The <code class="directive">StartServers</code> directive sets the
+ number of child server processes created on startup. As the number
+ of processes is dynamically controlled depending on the load,
+ there is usually little reason to adjust this parameter.</p>
+
+ <p>The default value differs from MPM to MPM. For
+ <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> and
+ <code class="module"><a href="../mod/worker.html">worker</a></code> the default is <code>StartServers 3</code>.
+ For <code class="module"><a href="../mod/prefork.html">prefork</a></code> defaults to <code>5</code> and for
+ <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> to <code>2</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="StartThreads" id="StartThreads">StartThreads</a> <a name="startthreads" id="startthreads">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created on startup</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartThreads <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code></td></tr>
+</table>
+ <p>Number of threads created on startup. As the
+ number of threads is dynamically controlled depending on the
+ load, there is usually little reason to adjust this
+ parameter.</p>
+
+ <p>For <code class="module"><a href="../mod/perchild.html">perchild</a></code> the default is <code>StartThreads
+ 5</code> and this directive tracks the number of threads per
+ process at startup.</p>
+
+ <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
+ <code>StartThreads 50</code> and, since there is only a single
+ process, this is the total number of threads created at startup to
+ serve requests.</p>
+
+ <p>For <code class="module"><a href="../mod/beos.html">beos</a></code> the default is <code>StartThreads
+ 10</code>. It also reflects the total number of threads created
+ at startup to serve requests.</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="ThreadLimit" id="ThreadLimit">ThreadLimit</a> <a name="threadlimit" id="threadlimit">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the upper limit on the configurable number of threads
+per child process</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadLimit <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available for <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> in Apache 2.0.41
+and later</td></tr>
+</table>
+ <p>This directive sets the maximum configured value for <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the lifetime
+ of the Apache process. Any attempts to change this directive
+ during a restart will be ignored, but <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> can be modified
+ during a restart up to the value of this directive.</p>
+
+ <p>Special care must be taken when using this directive. If
+ <code class="directive">ThreadLimit</code> is set to a value much higher
+ than <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>,
+ extra unused shared memory will be allocated. If both
+ <code class="directive">ThreadLimit</code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> are set to values
+ higher than the system can handle, Apache may not start or the
+ system may become unstable. Do not set the value of this directive
+ any higher than your greatest predicted setting of <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the
+ current run of Apache.</p>
+
+ <p>The default value for <code class="directive">ThreadLimit</code> is
+ <code>1920</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
+ <code>64</code> when used with the others.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>There is a hard limit of <code>ThreadLimit 20000</code> (or
+ <code>ThreadLimit 15000</code> with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>)
+ compiled into the server. This is intended to avoid nasty effects
+ caused by typos.</p>
+ </div>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ThreadsPerChild" id="ThreadsPerChild">ThreadsPerChild</a> <a name="threadsperchild" id="threadsperchild">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created by each child process</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadsPerChild <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+</table>
+ <p>This directive sets the number of threads created by each
+ child process. The child creates these threads at startup and
+ never creates more. If using an MPM like <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>,
+ where there is only one child process, this number should be high
+ enough to handle the entire load of the server. If using an MPM
+ like <code class="module"><a href="../mod/worker.html">worker</a></code>, where there are multiple child processes,
+ the <em>total</em> number of threads should be high enough to handle
+ the common load on the server.</p>
+
+ <p>The default value for <code class="directive">ThreadsPerChild</code> is
+ <code>64</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
+ <code>25</code> when used with the others.</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="User" id="User">User</a> <a name="user" id="user">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The userid under which the server will answer
+requests</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>User <var>unix-userid</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>User #-1</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>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only valid in global server config since Apache
+2.0</td></tr>
+</table>
+ <p>The <code class="directive">User</code> directive sets the user ID as
+ which the server will answer requests. In order to use this
+ directive, the server must be run initially as <code>root</code>.
+ If you start the server as a non-root user, it will fail to change
+ to the lesser privileged user, and will instead continue to run as
+ that original user. If you do start the server as <code>root</code>,
+ then it is normal for the parent process to remain running as root.
+ <var>Unix-userid</var> is one of:</p>
+
+ <dl>
+ <dt>A username</dt>
+ <dd>Refers to the given user by name.</dd>
+
+ <dt># followed by a user number.</dt>
+ <dd>Refers to a user by its number.</dd>
+ </dl>
+
+ <p>The user should have no privileges that result in it being
+ able to access files that are not intended to be visible to the
+ outside world, and similarly, the user should not be able to
+ execute code that is not meant for HTTP requests. It is
+ recommended that you set up a new user and group specifically for
+ running the server. Some admins use user <code>nobody</code>, but
+ this is not always desirable, since the <code>nobody</code> user
+ can have other uses on the system.</p>
+
+ <div class="warning"><h3>Security</h3>
+ <p>Don't set <code class="directive">User</code> (or <code class="directive"><a href="#group">Group</a></code>) to <code>root</code> unless
+ you know exactly what you are doing, and what the dangers are.</p>
+ </div>
+
+ <p>With the <code class="module"><a href="../mod/perchild.html">perchild</a></code> MPM, which is intended to
+ server virtual hosts run under different user IDs, the
+ <code class="directive">User</code> directive defines the user ID for the
+ main server and the fallback for <code class="directive"><a href="../mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code> sections without an
+ <code class="directive"><a href="../mod/perchild.html#assignuserid">AssignUserID</a></code> directive.</p>
+
+ <p>Special note: Use of this directive in <code class="directive"><a href="../mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code> is no longer supported. To
+ configure your server for <code class="program"><a href="../programs/suexec.html">suexec</a></code> use
+ <code class="directive"><a href="../mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>Although the <code class="directive">User</code> directive is present
+ in the <code class="module"><a href="../mod/beos.html">beos</a></code> and <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> MPMs,
+ it is actually a no-op there and only exists for compatibility
+ reasons.</p>
+ </div>
+
+</div>
+</div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
+<a href="../en/mod/mpm_common.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../es/mod/mpm_common.html" hreflang="es" rel="alternate" title="Español">&nbsp;es&nbsp;</a> |
+<a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
+</div><div id="footer">
+<p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
+</body></html> \ No newline at end of file