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<html xmlns="http://www.w3.org/TR/xhtml1/strict"><head><!--
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--><title>mpm_common - Apache HTTP Server</title><link rel="stylesheet" type="text/css" href="../style/manual.css"/></head><body><blockquote><div align="center"><img src="../images/sub.gif" alt="[APACHE DOCUMENTATION]"/><h3>Apache HTTP Server Version 2.0</h3></div><h1 align="center">Apache Module mpm_common</h1><table bgcolor="#cccccc" cellpadding="0" cellspacing="1"><tr><td><table bgcolor="#ffffff"><tr><td valign="top"><span class="help">Description:</span></td><td>A collection of directives that are implemented by
more than one multi-processing module (MPM)</td></tr><tr><td><a class="help" href="module-dict.html#Status">Status:</a></td><td>MPM</td></tr></table></td></tr></table><h2>Directives</h2><ul><li><a href="#coredumpdirectory">CoreDumpDirectory</a></li><li><a href="#group">Group</a></li><li><a href="#listen">Listen</a></li><li><a href="#listenbacklog">ListenBackLog</a></li><li><a href="#lockfile">LockFile</a></li><li><a href="#maxclients">MaxClients</a></li><li><a href="#maxrequestsperchild">MaxRequestsPerChild</a></li><li><a href="#maxsparethreads">MaxSpareThreads</a></li><li><a href="#maxthreadsperchild">MaxThreadsPerChild</a></li><li><a href="#minsparethreads">MinSpareThreads</a></li><li><a href="#numservers">NumServers</a></li><li><a href="#pidfile">PidFile</a></li><li><a href="#scoreboardfile">ScoreBoardFile</a></li><li><a href="#sendbuffersize">SendBufferSize</a></li><li><a href="#serverlimit">ServerLimit</a></li><li><a href="#startservers">StartServers</a></li><li><a href="#startthreads">StartThreads</a></li><li><a href="#threadlimit">ThreadLimit</a></li><li><a href="#threadsperchild">ThreadsPerChild</a></li><li><a href="#user">User</a></li></ul><hr/><h2><a name="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Sets the directory where Apache attempts to
switch before dumping core</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>CoreDumpDirectory <em>directory</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>See usage for the default setting</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code>, <code><a href="mpm_winnt.html">mpm_winnt</a></code></td></tr></table></td></tr></table>
<p>This controls the directory to which Apache attempts to
switch before dumping core. The default is in the
<a class="directive" href="core.html#serverroot"><code class="directive">ServerRoot</code></a> 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>
<hr/><h2><a name="Group">Group</a> <a name="group">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Sets the group under which the server will answer
requests</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>Group <em>unix-group</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>Group #-1</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config, virtual host</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code></td></tr></table></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 stand-alone server must be run initially as root.
<em>Unix-group</em> is one of:</p>
<dl>
<dt>A group name</dt>
<dd>Refers to the given group by name.</dd>
<dt># followed by a group number.</dt>
<dd>Refers to a group by its number.</dd>
</dl>
<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>
<p>Note: 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.</p>
<p>Special note: Use of this directive in <VirtualHost< is
no longer supported. To implement the <a href="../suexec.html">suEXEC wrapper</a> with Apache 2.0, use the
<a class="directive" href="mod_suexec.html#suexecusergroup"><code class="directive">SuexecUserGroup</code></a>
directive. SECURITY: See <a class="directive" href="#user"><code class="directive">User</code></a> for a discussion of the
security considerations.</p>
<hr/><h2><a name="Listen">Listen</a> <a name="listen">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Sets the IP addresses and ports that the server
listens to</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>Listen [<em>IP-address</em>:]<em>portnumber</em></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code>, <code><a href="mpm_winnt.html">mpm_winnt</a></code></td></tr></table></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. The Listen directive 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 Listen 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 Listen 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>
<blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
Listen 80<br/>
Listen 8000
</code></td></tr></table></blockquote>
<p>To make the server accept connections on two specified
interfaces and port numbers, use </p>
<blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
Listen 192.170.2.1:80<br/>
Listen 192.170.2.5:8000
</code></td></tr></table></blockquote>
<p>IPv6 addresses must be surrounded in square brackets, as in the
following example:</p>
<blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
Listen [fe80::a00:20ff:fea7:ccea]:80
</code></td></tr></table></blockquote>
<p><strong>See also </strong></p><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><hr/><h2><a name="ListenBackLog">ListenBackLog</a> <a name="listenbacklog">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Maximum length of the queue of pending connections</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>ListenBacklog <em>backlog</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>ListenBacklog 511</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code>, <code><a href="mpm_winnt.html">mpm_winnt</a></code></td></tr></table></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>
<hr/><h2><a name="LockFile">LockFile</a> <a name="lockfile">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Location of the accept serialization lock file</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>LockFile <em>filename</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>LockFile logs/accept.lock</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code></td></tr></table></td></tr></table>
<p>The <code class="directive">LockFile</code> directive sets the path to
the lockfile used when Apache is compiled with either
USE_FCNTL_SERIALIZED_ACCEPT or USE_FLOCK_SERIALIZED_ACCEPT. 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>
<p><strong>SECURITY:</strong> It is best to avoid 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>
<hr/><h2><a name="MaxClients">MaxClients</a> <a name="maxclients">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Maximum number of child processes that will be created
to serve requests</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>MaxClients <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>>MaxClients
8 (with threads) MaxClients 256</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="prefork.html">prefork</a></code></td></tr></table></td></tr></table>
<p>The <code class="directive">MaxClients</code> directive sets the limit
on the number of child processes that will be created to serve
requests. When the server is built without threading, no more than
this number of clients can be served simultaneously. To configure
more than 256 clients with the prefork MPM, you must use the
<a class="directive" href="#serverlimit"><code class="directive">ServerLimit</code></a> directive.
To configure more than 1024 clients with the worker MPM, you must
use the <a class="directive" href="#serverlimit"><code class="directive">ServerLimit</code></a> and
<a class="directive" href="#threadlimit"><code class="directive">ThreadLimit</code></a> directives.</p>
<p>Any connection attempts over the
<code class="directive">MaxClients</code> limit will normally be queued,
up to a number based on the <a class="directive" href="#listenbacklog"><code class="directive">ListenBacklog</code></a> directive. Once a child
process is freed at the end of a different request, the connection
will then be serviced.</p>
<p>When the server is compiled with threading, then the maximum
number of simultaneous requests that can be served is obtained
from the value of this directive multiplied by
<a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a>.</p>
<hr/><h2><a name="MaxRequestsPerChild">MaxRequestsPerChild</a> <a name="maxrequestsperchild">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Limit on the number of requests that an individual child server
will handle during its life</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>MaxRequestsPerChild <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>MaxRequestsPerChild 10000</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code>, <code><a href="mpm_winnt.html">mpm_winnt</a></code></td></tr></table></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
0, then the process will never expire.</p>
<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>
<p><strong>NOTE:</strong> For <em>KeepAlive</em> 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>
<hr/><h2><a name="MaxSpareThreads">MaxSpareThreads</a> <a name="maxsparethreads">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Maximum number of idle threads</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>MaxSpareThreads <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>MaxSpareThreads 10 (Perchild) or 500 (worker)</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code></td></tr></table></td></tr></table>
<p>Maximum number of idle threads. Different MPMs deal with this
directive differently. <code><a href="perchild.html">perchild</a></code> 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><code><a href="worker.html">worker</a></code> deals 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><strong>See also </strong></p><ul><li><a class="directive" href="#minsparethreads"><code class="directive">MinSpareThreads</code></a></li><li><a class="directive" href="#startservers"><code class="directive">StartServers</code></a></li></ul><hr/><h2><a name="MaxThreadsPerChild">MaxThreadsPerChild</a> <a name="maxthreadsperchild">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Maximum number of threads per child process</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>MaxThreadsPerChild <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>MaxThreadsPerChild 64</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code></td></tr></table></td></tr></table>
<p>Maximum number of threads per child. For MPMs with a
variable number of threads per child, this directive sets the
maximum number of threads that will be created in each child
process. To increase this value beyond its default, it is
necessary to change the value of the compile-time define
<code>HARD_THREAD_LIMIT</code> and recompile the server.</p>
<hr/><h2><a name="MinSpareThreads">MinSpareThreads</a> <a name="minsparethreads">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Minimum number of idle threads available to handle request
spikes</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>MinSpareServers <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>MinSpareThreads 5 (Perchild) or 250 (worker)</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code></td></tr></table></td></tr></table>
<p>Minimum number of idle threads to handle request spikes.
Different MPMs deal with this directive
differently. <code><a href="perchild.html">perchild</a></code> 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.</p>
<p><code><a href="worker.html">worker</a></code> deals 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><strong>See also </strong></p><ul><li><a class="directive" href="#maxsparethreads"><code class="directive">MaxSpareThreads</code></a></li><li><a class="directive" href="#startservers"><code class="directive">StartServers</code></a></li></ul><hr/><h2><a name="NumServers">NumServers</a> <a name="numservers">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Total number of children alive at the same time</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>NumServers <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>NumServers 2</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="perchild.html">perchild</a></code></td></tr></table></td></tr></table>
<p>Number of children alive at the same time. MPMs that use
this directive do not dynamically create new child processes so
this number should be large enough to handle the requests for
the entire site.</p>
<hr/><h2><a name="PidFile">PidFile</a> <a name="pidfile">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Sets the file where the server records the process ID
of the daemon</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>PidFile <em>filename</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>PidFile logs/httpd.pid</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchilde.html">perchilde</a></code>, <code><a href="prefork.html">prefork</a></code>, <code><a href="mpm_winnt.html">mpm_winnt</a></code></td></tr></table></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 does not begin with a slash (/) then it is assumed to be
relative to the <a class="directive" href="core.html#serverroot"><code class="directive">ServerRoot</code></a>.</p>
<p>It is often useful to be able to send the server a signal,
so that it closes and then reopens its <a class="directive" href="core.html#errorlog"><code class="directive">ErrorLog</code></a> and TransferLog, and
re-reads its configuration files. This is done by sending a
SIGHUP (kill -1) signal to the process id listed in the
PidFile.</p>
<p>The PidFile is subject to the same warnings about log file
placement and <a href="../misc/security_tips.html#serverroot">security</a>.</p>
<hr/><h2><a name="ScoreBoardFile">ScoreBoardFile</a> <a name="scoreboardfile">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Location of the file used to store coordination data for
the child processes</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>ScoreBoardFile <em>file-path</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>ScoreBoardFile logs/apache_status</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code></td></tr></table></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>
<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>
<p><strong>See also </strong></p><ul><li><a href="../stopping.html">Stopping and Restarting Apache</a></li></ul><hr/><h2><a name="SendBufferSize">SendBufferSize</a> <a name="sendbuffersize">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>TCP buffer size</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>SendBufferSize <em>bytes</em></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code>, <code><a href="mpm_winnt.html">mpm_winnt</a></code></td></tr></table></td></tr></table>
<p>The server will set the TCP 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>
<hr/><h2><a name="ServerLimit">ServerLimit</a> <a name="serverlimit">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Upper limit on configurable number of processes</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>ServerLimit <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>ServerLimit 256 (prefork), ServerLimit 16 (worker)</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="prefork.html">prefork</a></code></td></tr></table></td></tr></table>
<p>For the <code><a href="prefork.html">prefork</a></code> MPM, this directive sets the
maximum configured value for <a class="directive" href="#maxclients"><code class="directive">MaxClients</code></a> for the lifetime of the
Apache process. For the worker MPM, this directive in combination
with <a class="directive" href="#threadlimit"><code class="directive">ThreadLimit</code></a> sets
the maximum configured value for <a class="directive" href="#maxclients"><code class="directive">MaxClients</code></a> for the lifetime of the
Apache process. Any attempts to change this directive during a
restart will be ignored, but <a class="directive" href="#maxclients"><code class="directive">MaxClients</code></a> 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 <a class="directive" href="#maxclients"><code class="directive">MaxClients</code></a> 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><a href="prefork.html">prefork</a></code> MPM, use this directive only
if you need to set <a class="directive" href="#maxclients"><code class="directive">MaxClients</code></a> higher higher than 256.
Do not set the value of this directive any higher than what you
might want to set <a class="directive" href="#maxclients"><code class="directive">MaxClients</code></a> to.</p>
<p>With the <code><a href="worker.html">worker</a></code> MPM, use this directive only
if your <a class="directive" href="#maxclients"><code class="directive">MaxClients</code></a> and
<a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a>
settings require more than 16 server processes. Do not set the
value of this directive any higher than the number of server
processes required by what you may want for <a class="directive" href="#maxclients "><code class="directive">MaxClients </code></a> and <a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a>.</p>
<hr/><h2><a name="StartServers">StartServers</a> <a name="startservers">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Number of child server processes created at startup</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>StartServers <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>StartServers 5</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code></td></tr></table></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><strong>See also </strong></p><ul><li><a class="directive" href="#minsparethreads"><code class="directive">MinSpareThreads</code></a></li><li><a class="directive" href="#maxsparethreads"><code class="directive">MaxSpareThreads</code></a></li></ul><hr/><h2><a name="StartThreads">StartThreads</a> <a name="startthreads">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Nubmer of threads each child creates on startup</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>StartThreads <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>StartThreads 5</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="perchild.html">perchild</a></code></td></tr></table></td></tr></table>
<p>Number of threads each child creates on startup. As the
number of threads is dynamically controlled depending on the
load, there is usually little reason to adjust this
parameter.</p>
<hr/><h2><a name="ThreadLimit">ThreadLimit</a> <a name="threadlimit">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Sets the upper limit on the configurable number of threads
per child process</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>ThreadLimit <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>ThreadLimit 64</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code></td></tr></table></td></tr></table>
<p>This directive sets the maximum configured value for <a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a> for the lifetime
of the Apache process. Any attempts to change this directive
during a restart will be ignored, but <a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a> 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 <a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a>,
extra unused shared memory will be allocated. If both
<code class="directive">ThreadLimit</code> and <a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a> are set to values
higher than the system can handle, Apache may not start or the
system may become unstable.</p>
<p>Use this directive only if you need to set <a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a> higher than 64. Do
not set the value of this directive any higher than what you might
want to set <a class="directive" href="#threadsperchild"><code class="directive">ThreadsPerChild</code></a> to.</p>
<hr/><h2><a name="ThreadsPerChild">ThreadsPerChild</a> <a name="threadsperchild">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Number of threads created by each child process</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>ThreadsPerChild <em>number</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>ThreadsPerChild 50</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="mpm_winnt.html">mpm_winnt</a></code></td></tr></table></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 mpmt_winnt, 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 worker, where there are multiple child processes, the
total number of threads should be high enough to handle the
common load on the server.</p>
<hr/><h2><a name="User">User</a> <a name="user">Directive</a></h2><table bgcolor="#cccccc" border="0" cellspacing="0" cellpadding="1"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>The userid under which the server will answer
requests</td></tr><tr><td><a class="help" href="directive-dict.html#Syntax">Syntax:</a></td><td>User <em>unix-userid</em></td></tr><tr><td><a class="help" href="directive-dict.html#Default">Default:</a></td><td><code>User #-1</code></td></tr><tr><td><a class="help" href="directive-dict.html#Context">Context:</a></td><td>server config, virtual host</td></tr><tr><td><a class="help" href="directive-dict.html#Status">Status:</a></td><td>MPM</td></tr><tr><td><a class="help" href="directive-dict.html#Module">Module:</a></td><td><code><a href="worker.html">worker</a></code>, <code><a href="perchild.html">perchild</a></code>, <code><a href="prefork.html">prefork</a></code></td></tr></table></td></tr></table>
<p>The <code class="directive">User</code> directive sets the userid as
which the server will answer requests. In order to use this
directive, the standalone server must be run initially as
root. <em>Unix-userid</em> 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 their number.</dd>
</dl>
<p>The user should have no privileges which result in it being
able to access files which are not intended to be visible to the
outside world, and similarly, the user should not be able to
execute code which is not meant for httpd 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 possible or desirable. For example
<code><a href="mod_proxy.html">mod_proxy</a></code>'s cache, when enabled, must be
accessible to this user (see <a class="directive" href="mod_proxy.html#cacheroot"><code class="directive">CacheRoot</code></a>).</p>
<p>Notes: 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 root, then it is normal for the parent process to
remain running as root.</p>
<p>Special note: Use of this directive in <a class="directive" href="core.html#virtualhost"><code class="directive"><VirtualHost></code></a> is no longer supported. To
configure your server for <a href="mod_suexec.html">suexec</a> use
<a class="directive" href="mod_suexec.html#suexecusergroup"><code class="directive">SuexecUserGroup</code></a>.</p>
<blockquote><table><tr><td bgcolor="#e0e5f5"><p align="center"><strong>Security</strong></p> <p>Don't set <code class="directive">User</code>
(or <a class="directive" href="#group"><code class="directive">Group</code></a>) to
<code>root</code> unless you know exactly what you are doing, and what
the dangers are.</p></td></tr></table></blockquote>
<hr/><h3 align="center">Apache HTTP Server Version 2.0</h3><a href="./"><img src="../images/index.gif" alt="Index"/></a><a href="../"><img src="../images/home.gif" alt="Home"/></a></blockquote></body></html>
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