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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">
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-->
<title>mpm_common - Apache HTTP Server</title>
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<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>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.0</a> > <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"> de </a> |
<a href="../en/mod/mpm_common.html" title="English"> en </a> |
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</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"><VirtualHost></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 child processes that will be created
to serve requests</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 limit has two beneficial effects:</p>
<ul>
<li>it limits the amount of memory that process can consume
by (accidental) memory leakage;</li>
<li>by giving processes a finite lifetime, it helps reduce
the number of processes when the server load reduces.</li>
</ul>
<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"><VirtualHost></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"><VirtualHost></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>
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