1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- 4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 5 This file is generated from xml source: DO NOT EDIT 6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 7 --> 8<title>mpm_common - Apache HTTP Server</title> 9<link href="/style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> 10<link href="/style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> 11<link href="/style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="/style/css/prettify.css" /> 12<script src="/style/scripts/prettify.js" type="text/javascript"> 13</script> 14 15<link href="/images/favicon.ico" rel="shortcut icon" /></head> 16<body> 17<div id="page-header"> 18<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p> 19<p class="apache">Apache HTTP Server Version 2.2</p> 20<img alt="" src="/images/feather.gif" /></div> 21<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div> 22<div id="path"> 23<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 2.2</a> > <a href="./">Modules</a></div> 24<div id="page-content"> 25<div id="preamble"><h1>Apache MPM Common Directives</h1> 26<div class="toplang"> 27<p><span>Available Languages: </span><a href="/de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | 28<a href="/en/mod/mpm_common.html" title="English"> en </a> | 29<a href="/ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 30<a href="/tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p> 31</div> 32<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A collection of directives that are implemented by 33more than one multi-processing module (MPM)</td></tr> 34<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr></table> 35</div> 36<div id="quickview"><h3 class="directives">Directives</h3> 37<ul id="toc"> 38<li><img alt="" src="/images/down.gif" /> <a href="#acceptmutex">AcceptMutex</a></li> 39<li><img alt="" src="/images/down.gif" /> <a href="#chrootdir">ChrootDir</a></li> 40<li><img alt="" src="/images/down.gif" /> <a href="#coredumpdirectory">CoreDumpDirectory</a></li> 41<li><img alt="" src="/images/down.gif" /> <a href="#enableexceptionhook">EnableExceptionHook</a></li> 42<li><img alt="" src="/images/down.gif" /> <a href="#gracefulshutdowntimeout">GracefulShutdownTimeout</a></li> 43<li><img alt="" src="/images/down.gif" /> <a href="#group">Group</a></li> 44<li><img alt="" src="/images/down.gif" /> <a href="#listen">Listen</a></li> 45<li><img alt="" src="/images/down.gif" /> <a href="#listenbacklog">ListenBackLog</a></li> 46<li><img alt="" src="/images/down.gif" /> <a href="#lockfile">LockFile</a></li> 47<li><img alt="" src="/images/down.gif" /> <a href="#maxclients">MaxClients</a></li> 48<li><img alt="" src="/images/down.gif" /> <a href="#maxmemfree">MaxMemFree</a></li> 49<li><img alt="" src="/images/down.gif" /> <a href="#maxrequestsperchild">MaxRequestsPerChild</a></li> 50<li><img alt="" src="/images/down.gif" /> <a href="#maxsparethreads">MaxSpareThreads</a></li> 51<li><img alt="" src="/images/down.gif" /> <a href="#minsparethreads">MinSpareThreads</a></li> 52<li><img alt="" src="/images/down.gif" /> <a href="#pidfile">PidFile</a></li> 53<li><img alt="" src="/images/down.gif" /> <a href="#receivebuffersize">ReceiveBufferSize</a></li> 54<li><img alt="" src="/images/down.gif" /> <a href="#scoreboardfile">ScoreBoardFile</a></li> 55<li><img alt="" src="/images/down.gif" /> <a href="#sendbuffersize">SendBufferSize</a></li> 56<li><img alt="" src="/images/down.gif" /> <a href="#serverlimit">ServerLimit</a></li> 57<li><img alt="" src="/images/down.gif" /> <a href="#startservers">StartServers</a></li> 58<li><img alt="" src="/images/down.gif" /> <a href="#startthreads">StartThreads</a></li> 59<li><img alt="" src="/images/down.gif" /> <a href="#threadlimit">ThreadLimit</a></li> 60<li><img alt="" src="/images/down.gif" /> <a href="#threadsperchild">ThreadsPerChild</a></li> 61<li><img alt="" src="/images/down.gif" /> <a href="#threadstacksize">ThreadStackSize</a></li> 62<li><img alt="" src="/images/down.gif" /> <a href="#user">User</a></li> 63</ul> 64<ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 65 66<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 67<div class="directive-section"><h2><a name="AcceptMutex" id="AcceptMutex">AcceptMutex</a> <a name="acceptmutex" id="acceptmutex">Directive</a></h2> 68<table class="directive"> 69<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Method that Apache uses to serialize multiple children 70accepting requests on network sockets</td></tr> 71<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AcceptMutex Default|<var>method</var></code></td></tr> 72<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AcceptMutex Default</code></td></tr> 73<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 74<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 75<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 76</table> 77 <p>The <code class="directive">AcceptMutex</code> directives sets the 78 method that Apache uses to serialize multiple children accepting 79 requests on network sockets. Prior to Apache 2.0, the method was 80 selectable only at compile time. The optimal method to use is 81 highly architecture and platform dependent. For further details, 82 see the <a href="/misc/perf-tuning.html">performance tuning</a> 83 documentation.</p> 84 85 <p>If this directive is set to <code>Default</code>, then the 86 compile-time selected default will be used. Other possible 87 methods are listed below. Note that not all methods are 88 available on all platforms. If a method is specified which is 89 not available, a message will be written to the error log 90 listing the available methods.</p> 91 92 <dl> 93 <dt><code>flock</code></dt> 94 <dd>uses the <code>flock(2)</code> system call to lock the 95 file defined by the <code class="directive"><a href="#lockfile">LockFile</a></code> directive.</dd> 96 97 <dt><code>fcntl</code></dt> 98 <dd>uses the <code>fcntl(2)</code> system call to lock the 99 file defined by the <code class="directive"><a href="#lockfile">LockFile</a></code> directive.</dd> 100 101 <dt><code>posixsem</code></dt> 102 <dd>uses POSIX compatible semaphores to implement the mutex.</dd> 103 104 <dt><code>pthread</code></dt> 105 <dd>uses POSIX mutexes as implemented by the POSIX Threads 106 (PThreads) specification.</dd> 107 108 <dt><code>sysvsem</code></dt> 109 <dd>uses SySV-style semaphores to implement the mutex.</dd> 110 </dl> 111 112 <p>If you want to find out the compile time chosen default 113 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> 114 115 <div class="warning"><h3>Warning</h3> 116 <p>On most systems, when the <code>pthread</code> option 117 is selected, if a child process terminates abnormally 118 while holding the <code>AcceptCntl</code> mutex the 119 server will stop responding to requests. When this 120 occurs, the server will require a manual restart to 121 recover.</p> 122 <p>Solaris is a notable exception as it provides a 123 mechanism, used by Apache, which usually allows the 124 mutex to be recovered after a child process terminates 125 abnormally while holding a mutex.</p> 126 <p>If your system implements the 127 <code>pthread_mutexattr_setrobust_np()</code> function, 128 you may be able to use the <code>pthread</code> option safely.</p> 129 </div> 130 131</div> 132<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 133<div class="directive-section"><h2><a name="ChrootDir" id="ChrootDir">ChrootDir</a> <a name="chrootdir" id="chrootdir">Directive</a></h2> 134<table class="directive"> 135<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory for apache to run chroot(8) after startup.</td></tr> 136<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ChrootDir <var>/path/to/directory</var></code></td></tr> 137<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr> 138<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 139<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 140<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/event.html">event</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 141<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.2.10 and later</td></tr> 142</table> 143 <p>This directive tells the server to <var>chroot(8)</var> to the 144 specified directory after startup, but before accepting requests.</p> 145 146 <p>Note that running the server under chroot is not 147 simple, and requires additional setup, particularly if you are running 148 scripts such as CGI or PHP. Please make sure you are properly familiar 149 with the operation of chroot before attempting to use this feature.</p> 150 151</div> 152<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 153<div class="directive-section"><h2><a name="CoreDumpDirectory" id="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory" id="coredumpdirectory">Directive</a></h2> 154<table class="directive"> 155<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory where Apache attempts to 156switch before dumping core</td></tr> 157<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CoreDumpDirectory <var>directory</var></code></td></tr> 158<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for the default setting</code></td></tr> 159<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 160<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 161<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_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 162</table> 163 <p>This controls the directory to which Apache attempts to 164 switch before dumping core. The default is in the 165 <code class="directive"><a href="/mod/core.html#serverroot">ServerRoot</a></code> directory, however 166 since this should not be writable by the user the server runs 167 as, core dumps won't normally get written. If you want a core 168 dump for debugging, you can use this directive to place it in a 169 different location.</p> 170 171 <div class="note"><h3>Core Dumps on Linux</h3> 172 <p>If Apache starts as root and switches to another user, the 173 Linux kernel <em>disables</em> core dumps even if the directory is 174 writable for the process. Apache (2.0.46 and later) reenables core dumps 175 on Linux 2.4 and beyond, but only if you explicitly configure a <code class="directive">CoreDumpDirectory</code>.</p> 176 </div> 177 178 <div class="note"><h3>Core Dumps on BSD</h3> 179 <p>To enable core-dumping of suid-executables on BSD-systems (such 180 as FreeBSD), set <code>kern.sugid_coredump</code> to 1. 181 </p></div> 182 183 184</div> 185<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 186<div class="directive-section"><h2><a name="EnableExceptionHook" id="EnableExceptionHook">EnableExceptionHook</a> <a name="enableexceptionhook" id="enableexceptionhook">Directive</a></h2> 187<table class="directive"> 188<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a hook that runs exception handlers 189after a crash</td></tr> 190<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableExceptionHook On|Off</code></td></tr> 191<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableExceptionHook Off</code></td></tr> 192<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 193<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 194<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 195<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.49 and later</td></tr> 196</table> 197 <p>For safety reasons this directive is only available if the server was 198 configured with the <code>--enable-exception-hook</code> option. It 199 enables a hook that allows external modules to plug in and do something 200 after a child crashed.</p> 201 202 <p>There are already two modules, <code>mod_whatkilledus</code> and 203 <code>mod_backtrace</code> that make use of this hook. Please have a 204 look at Jeff Trawick's <a href="http://www.apache.org/~trawick/exception_hook.html">EnableExceptionHook site</a> for more information about these.</p> 205 206</div> 207<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 208<div class="directive-section"><h2><a name="GracefulShutdownTimeout" id="GracefulShutdownTimeout">GracefulShutdownTimeout</a> <a name="gracefulshutdowntimeout" id="gracefulshutdowntimeout">Directive</a></h2> 209<table class="directive"> 210<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a timeout after which a gracefully shutdown server 211will exit.</td></tr> 212<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>GracefulShutDownTimeout <var>seconds</var></code></td></tr> 213<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>GracefulShutDownTimeout 0</code></td></tr> 214<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 215<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 216<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code>, <code class="module"><a href="/mod/event.html">event</a></code></td></tr> 217<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.2 and later</td></tr> 218</table> 219 <p>The <code class="directive">GracefulShutdownTimeout</code> specifies 220 how many seconds after receiving a "graceful-stop" signal, a 221 server should continue to run, handling the existing connections.</p> 222 223 <p>Setting this value to zero means that the server will wait 224 indefinitely until all remaining requests have been fully served.</p> 225 226</div> 227<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 228<div class="directive-section"><h2><a name="Group" id="Group">Group</a> <a name="group" id="group">Directive</a></h2> 229<table class="directive"> 230<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Group under which the server will answer 231requests</td></tr> 232<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Group <var>unix-group</var></code></td></tr> 233<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Group #-1</code></td></tr> 234<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 235<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 236<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/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 237<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only valid in global server config since Apache 2382.0</td></tr> 239</table> 240 <p>The <code class="directive">Group</code> directive sets the group under 241 which the server will answer requests. In order to use this 242 directive, the server must be run initially as <code>root</code>. If 243 you start the server as a non-root user, it will fail to change to the 244 specified group, and will instead continue to run as the group of the 245 original user. <var>Unix-group</var> is one of:</p> 246 247 <dl> 248 <dt>A group name</dt> 249 <dd>Refers to the given group by name.</dd> 250 251 <dt><code>#</code> followed by a group number.</dt> 252 <dd>Refers to a group by its number.</dd> 253 </dl> 254 255 <div class="example"><h3>Example</h3><p><code> 256 Group www-group 257 </code></p></div> 258 259 <p>It is recommended that you set up a new group specifically for 260 running the server. Some admins use user <code>nobody</code>, 261 but this is not always possible or desirable.</p> 262 263 <div class="warning"><h3>Security</h3> 264 <p>Don't set <code class="directive">Group</code> (or <code class="directive"><a href="#user">User</a></code>) to <code>root</code> unless 265 you know exactly what you are doing, and what the dangers are.</p> 266 </div> 267 268 <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 269 configure your server for <code class="program"><a href="/programs/suexec.html">suexec</a></code> use 270 <code class="directive"><a href="/mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>.</p> 271 272 <div class="note"><h3>Note</h3> 273 <p>Although the <code class="directive">Group</code> directive is present 274 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, 275 it is actually a no-op there and only exists for compatibility 276 reasons.</p> 277 </div> 278 279</div> 280<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 281<div class="directive-section"><h2><a name="Listen" id="Listen">Listen</a> <a name="listen" id="listen">Directive</a></h2> 282<table class="directive"> 283<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>IP addresses and ports that the server 284listens to</td></tr> 285<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Listen [<var>IP-address</var>:]<var>portnumber</var> [<var>protocol</var>]</code></td></tr> 286<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 287<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 288<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/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/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code>, <code class="module"><a href="/mod/event.html">event</a></code></td></tr> 289<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Required directive since Apache 2.0<br /> 290The <var>protocol</var> argument was added in 2.1.5</td></tr> 291</table> 292 <p>The <code class="directive">Listen</code> directive instructs Apache to 293 listen to only specific IP addresses or ports; by default it 294 responds to requests on all IP interfaces. <code class="directive">Listen</code> 295 is now a required directive. If it is not in the config file, the 296 server will fail to start. This is a change from previous versions 297 of Apache.</p> 298 299 <p>The <code class="directive">Listen</code> directive tells the server to 300 accept incoming requests on the specified port or address-and-port 301 combination. If only a port number is specified, the server listens to 302 the given port on all interfaces. If an IP address is given as well 303 as a port, the server will listen on the given port and 304 interface.</p> 305 306 <p>Multiple <code class="directive">Listen</code> directives may be used to 307 specify a number of addresses and ports to listen to. The server will 308 respond to requests from any of the listed addresses and ports.</p> 309 310 <p>For example, to make the server accept connections on both 311 port 80 and port 8000, use:</p> 312 313 <div class="example"><p><code> 314 Listen 80<br /> 315 Listen 8000 316 </code></p></div> 317 318 <p>To make the server accept connections on two specified 319 interfaces and port numbers, use </p> 320 321 <div class="example"><p><code> 322 Listen 192.170.2.1:80<br /> 323 Listen 192.170.2.5:8000 324 </code></p></div> 325 326 <p>IPv6 addresses must be surrounded in square brackets, as in the 327 following example:</p> 328 329 <div class="example"><p><code> 330 Listen [2001:db8::a00:20ff:fea7:ccea]:80 331 </code></p></div> 332 333 <p>The optional <var>protocol</var> argument is not required for most 334 configurations. If not specified, <code>https</code> is the default for 335 port 443 and <code>http</code> the default for all other ports. The 336 protocol is used to determine which module should handle a request, and 337 to apply protocol specific optimizations with the 338 <code class="directive"><a href="/mod/core.html#acceptfilter">AcceptFilter</a></code> directive.</p> 339 340 <p>You only need to set the protocol if you are running on non-standard 341 ports. For example, running an <code>https</code> site on port 8443:</p> 342 343 <div class="example"><p><code> 344 Listen 192.170.2.1:8443 https 345 </code></p></div> 346 347 <div class="note"><h3>Error condition</h3> 348 Multiple <code class="directive">Listen</code> directives for the same ip 349 address and port will result in an <code>Address already in use</code> 350 error message. 351 </div> 352 353 354<h3>See also</h3> 355<ul> 356<li><a href="/dns-caveats.html">DNS Issues</a></li> 357<li><a href="/bind.html">Setting which addresses and ports Apache 358 uses</a></li> 359</ul> 360</div> 361<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 362<div class="directive-section"><h2><a name="ListenBackLog" id="ListenBackLog">ListenBackLog</a> <a name="listenbacklog" id="listenbacklog">Directive</a></h2> 363<table class="directive"> 364<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum length of the queue of pending connections</td></tr> 365<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenBacklog <var>backlog</var></code></td></tr> 366<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenBacklog 511</code></td></tr> 367<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 368<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 369<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/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/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 370</table> 371 <p>The maximum length of the queue of pending connections. 372 Generally no tuning is needed or desired, however on some 373 systems it is desirable to increase this when under a TCP SYN 374 flood attack. See the backlog parameter to the 375 <code>listen(2)</code> system call.</p> 376 377 <p>This will often be limited to a smaller number by the 378 operating system. This varies from OS to OS. Also note that 379 many OSes do not use exactly what is specified as the backlog, 380 but use a number based on (but normally larger than) what is 381 set.</p> 382 383</div> 384<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 385<div class="directive-section"><h2><a name="LockFile" id="LockFile">LockFile</a> <a name="lockfile" id="lockfile">Directive</a></h2> 386<table class="directive"> 387<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the accept serialization lock file</td></tr> 388<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LockFile <var>filename</var></code></td></tr> 389<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LockFile logs/accept.lock</code></td></tr> 390<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 391<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 392<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 393</table> 394 <p>The <code class="directive">LockFile</code> directive sets the path to 395 the lockfile used when Apache is used with an <code class="directive"><a href="#acceptmutex">AcceptMutex</a></code> value of either 396 <code>fcntl</code> or <code>flock</code>. This directive should 397 normally be left at its default value. The main reason for changing 398 it is if the <code>logs</code> directory is NFS mounted, since 399 <strong>the lockfile must be stored on a local disk</strong>. The PID 400 of the main server process is automatically appended to the 401 filename.</p> 402 403 <div class="warning"><h3>Security</h3> 404 <p>It is best to <em>avoid</em> putting this file in a world writable 405 directory such as <code>/var/tmp</code> because someone could create 406 a denial of service attack and prevent the server from starting by 407 creating a lockfile with the same name as the one the server will try 408 to create.</p> 409 </div> 410 411<h3>See also</h3> 412<ul> 413<li><code class="directive"><a href="#acceptmutex">AcceptMutex</a></code></li> 414</ul> 415</div> 416<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 417<div class="directive-section"><h2><a name="MaxClients" id="MaxClients">MaxClients</a> <a name="maxclients" id="maxclients">Directive</a></h2> 418<table class="directive"> 419<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of connections that will be processed 420simultaneously</td></tr> 421<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxClients <var>number</var></code></td></tr> 422<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr> 423<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 424<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 425<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/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 426</table> 427 <p>The <code class="directive">MaxClients</code> directive sets the limit 428 on the number of simultaneous requests that will be served. Any 429 connection attempts over the <code class="directive">MaxClients</code> 430 limit will normally be queued, up to a number based on the 431 <code class="directive"><a href="#listenbacklog">ListenBacklog</a></code> 432 directive. Once a child process is freed at the end of a different 433 request, the connection will then be serviced.</p> 434 435 <p>For non-threaded servers (<em>i.e.</em>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>), 436 <code class="directive">MaxClients</code> translates into the maximum 437 number of child processes that will be launched to serve requests. 438 The default value is <code>256</code>; to increase it, you must also raise 439 <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p> 440 441 <p>For threaded and hybrid servers (<em>e.g.</em> <code class="module"><a href="/mod/beos.html">beos</a></code> 442 or <code class="module"><a href="/mod/worker.html">worker</a></code>) <code class="directive">MaxClients</code> restricts 443 the total number of threads that will be available to serve clients. 444 The default value for <code class="module"><a href="/mod/beos.html">beos</a></code> is <code>50</code>. For 445 hybrid MPMs the default value is <code>16</code> (<code class="directive"><a href="#serverlimit">ServerLimit</a></code>) multiplied by the value of 446 <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, 447 you must also raise <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p> 448 449</div> 450<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 451<div class="directive-section"><h2><a name="MaxMemFree" id="MaxMemFree">MaxMemFree</a> <a name="maxmemfree" id="maxmemfree">Directive</a></h2> 452<table class="directive"> 453<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of memory that the main allocator is allowed 454to hold without calling <code>free()</code></td></tr> 455<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxMemFree <var>KBytes</var></code></td></tr> 456<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxMemFree 0</code></td></tr> 457<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 458<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 459<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/prefork.html">prefork</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> 460</table> 461 <p>The <code class="directive">MaxMemFree</code> directive sets the 462 maximum number of free Kbytes that the main allocator is allowed 463 to hold without calling <code>free()</code>. When not set, or when set 464 to zero, the threshold will be set to unlimited.</p> 465 466</div> 467<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 468<div class="directive-section"><h2><a name="MaxRequestsPerChild" id="MaxRequestsPerChild">MaxRequestsPerChild</a> <a name="maxrequestsperchild" id="maxrequestsperchild">Directive</a></h2> 469<table class="directive"> 470<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on the number of requests that an individual child server 471will handle during its life</td></tr> 472<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRequestsPerChild <var>number</var></code></td></tr> 473<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxRequestsPerChild 10000</code></td></tr> 474<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 475<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 476<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 477</table> 478 <p>The <code class="directive">MaxRequestsPerChild</code> directive sets 479 the limit on the number of requests that an individual child 480 server process will handle. After 481 <code class="directive">MaxRequestsPerChild</code> requests, the child 482 process will die. If <code class="directive">MaxRequestsPerChild</code> is 483 <code>0</code>, then the process will never expire.</p> 484 485 <div class="note"><h3>Different default values</h3> 486 <p>The default value for <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code> and 487 <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code> is <code>0</code>.</p> 488 </div> 489 490 <p>Setting <code class="directive">MaxRequestsPerChild</code> to a 491 non-zero value limits the amount of memory that process can consume 492 by (accidental) memory leakage.</p> 493 494 <div class="note"><h3>Note</h3> 495 <p>For <code class="directive"><a href="/mod/core.html#keepalive">KeepAlive</a></code> requests, only 496 the first request is counted towards this limit. In effect, it 497 changes the behavior to limit the number of <em>connections</em> per 498 child.</p> 499 </div> 500 <div class="note"><h3>Default Configuration</h3> 501 <p>The default (compiled-in) value of this setting (10000) is used when 502 no <code class="directive">MaxRequestsPerChild</code> directive is present in the 503 configuration. Many default configurations provided with the server include 504 "MaxRequestsPerChild 0" as part of the <em>default configuration</em>.</p> 505</div> 506 507 508</div> 509<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 510<div class="directive-section"><h2><a name="MaxSpareThreads" id="MaxSpareThreads">MaxSpareThreads</a> <a name="maxsparethreads" id="maxsparethreads">Directive</a></h2> 511<table class="directive"> 512<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle threads</td></tr> 513<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareThreads <var>number</var></code></td></tr> 514<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr> 515<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 516<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 517<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/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 518</table> 519 <p>Maximum number of idle threads. Different MPMs deal with this 520 directive differently.</p> 521 522 <p>For <code class="module"><a href="/mod/worker.html">worker</a></code>, 523 the default is <code>MaxSpareThreads 250</code>. 524 These MPMs deal with idle threads on a server-wide basis. If there 525 are too many idle threads in the server then child processes are 526 killed until the number of idle threads is less than this number.</p> 527 528 <p>For <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code> the default is 529 <code>MaxSpareThreads 100</code>. Since this MPM runs a 530 single-process, the spare thread count is also server-wide.</p> 531 532 <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 533 similar to <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code>. The default for 534 <code class="module"><a href="/mod/beos.html">beos</a></code> is <code>MaxSpareThreads 50</code>. For 535 <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>10</code>.</p> 536 537 <div class="note"><h3>Restrictions</h3> 538 <p>The range of the <code class="directive">MaxSpareThreads</code> value 539 is restricted. Apache will correct the given value automatically 540 according to the following rules:</p> 541 <ul> 542 543 <li><code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code> wants the value to be greater than 544 <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>.</li> 545 546 <li>For 547 <code class="module"><a href="/mod/worker.html">worker</a></code> the value must be greater or equal than 548 the sum of <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code> 549 and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</li> 550 </ul> 551 </div> 552 553<h3>See also</h3> 554<ul> 555<li><code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code></li> 556<li><code class="directive"><a href="#startservers">StartServers</a></code></li> 557</ul> 558</div> 559<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 560<div class="directive-section"><h2><a name="MinSpareThreads" id="MinSpareThreads">MinSpareThreads</a> <a name="minsparethreads" id="minsparethreads">Directive</a></h2> 561<table class="directive"> 562<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle threads available to handle request 563spikes</td></tr> 564<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareThreads <var>number</var></code></td></tr> 565<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr> 566<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 567<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 568<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/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 569</table> 570 <p>Minimum number of idle threads to handle request spikes. 571 Different MPMs deal with this directive 572 differently.</p> 573 574 575 <p><code class="module"><a href="/mod/worker.html">worker</a></code> 576 uses a default of <code>MinSpareThreads 577 75</code> and deal with idle threads on a server-wide basis. If 578 there aren't enough idle threads in the server then child 579 processes are created until the number of idle threads is greater 580 than number.</p> 581 582 <p><code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code> uses a default of 583 <code>MinSpareThreads 10</code> and, since it is a single-process 584 MPM, tracks this on a server-wide bases.</p> 585 586 <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 587 similar to <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code>. The default for 588 <code class="module"><a href="/mod/beos.html">beos</a></code> is <code>MinSpareThreads 1</code>. For 589 <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>5</code>.</p> 590 591<h3>See also</h3> 592<ul> 593<li><code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code></li> 594<li><code class="directive"><a href="#startservers">StartServers</a></code></li> 595</ul> 596</div> 597<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 598<div class="directive-section"><h2><a name="PidFile" id="PidFile">PidFile</a> <a name="pidfile" id="pidfile">Directive</a></h2> 599<table class="directive"> 600<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File where the server records the process ID 601of the daemon</td></tr> 602<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PidFile <var>filename</var></code></td></tr> 603<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>PidFile logs/httpd.pid</code></td></tr> 604<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 605<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 606<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_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/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 607</table> 608 <p>The <code class="directive">PidFile</code> directive sets the file to 609 which the server records the process id of the daemon. If the 610 filename is not absolute then it is assumed to be relative to the 611 <code class="directive"><a href="/mod/core.html#serverroot">ServerRoot</a></code>.</p> 612 613 <div class="example"><h3>Example</h3><p><code> 614 PidFile /var/run/apache.pid 615 </code></p></div> 616 617 <p>It is often useful to be able to send the server a signal, 618 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 619 re-reads its configuration files. This is done by sending a 620 SIGHUP (kill -1) signal to the process id listed in the 621 <code class="directive">PidFile</code>.</p> 622 623 <p>The <code class="directive">PidFile</code> is subject to the same 624 warnings about log file placement and <a href="/misc/security_tips.html#serverroot">security</a>.</p> 625 626 <div class="note"><h3>Note</h3> 627 <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> 628 </div> 629 630</div> 631<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 632<div class="directive-section"><h2><a name="ReceiveBufferSize" id="ReceiveBufferSize">ReceiveBufferSize</a> <a name="receivebuffersize" id="receivebuffersize">Directive</a></h2> 633<table class="directive"> 634<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP receive buffer size</td></tr> 635<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ReceiveBufferSize <var>bytes</var></code></td></tr> 636<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ReceiveBufferSize 0</code></td></tr> 637<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 638<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 639<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/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/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 640</table> 641 <p>The server will set the TCP receive buffer size to the number of 642 bytes specified.</p> 643 644 <p>If set to the value of <code>0</code>, the server will use the 645 OS default.</p> 646 647</div> 648<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 649<div class="directive-section"><h2><a name="ScoreBoardFile" id="ScoreBoardFile">ScoreBoardFile</a> <a name="scoreboardfile" id="scoreboardfile">Directive</a></h2> 650<table class="directive"> 651<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the file used to store coordination data for 652the child processes</td></tr> 653<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScoreBoardFile <var>file-path</var></code></td></tr> 654<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScoreBoardFile logs/apache_runtime_status</code></td></tr> 655<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 656<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 657<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_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 658</table> 659 <p>Apache uses a scoreboard to communicate between its parent 660 and child processes. Some architectures require a file to facilitate 661 this communication. If the file is left unspecified, Apache first 662 attempts to create the scoreboard entirely in memory (using anonymous 663 shared memory) and, failing that, will attempt to create the file on 664 disk (using file-based shared memory). Specifying this directive causes 665 Apache to always create the file on the disk.</p> 666 667 <div class="example"><h3>Example</h3><p><code> 668 ScoreBoardFile /var/run/apache_runtime_status 669 </code></p></div> 670 671 <p>File-based shared memory is useful for third-party applications 672 that require direct access to the scoreboard.</p> 673 674 <p>If you use a <code class="directive">ScoreBoardFile</code> then 675 you may see improved speed by placing it on a RAM disk. But be 676 careful that you heed the same warnings about log file placement 677 and <a href="/misc/security_tips.html">security</a>.</p> 678 679<h3>See also</h3> 680<ul> 681<li><a href="/stopping.html">Stopping and Restarting 682Apache</a></li> 683</ul> 684</div> 685<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 686<div class="directive-section"><h2><a name="SendBufferSize" id="SendBufferSize">SendBufferSize</a> <a name="sendbuffersize" id="sendbuffersize">Directive</a></h2> 687<table class="directive"> 688<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP buffer size</td></tr> 689<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SendBufferSize <var>bytes</var></code></td></tr> 690<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SendBufferSize 0</code></td></tr> 691<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 692<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 693<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/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/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 694</table> 695 <p>The server will set the TCP send buffer size to the number of bytes 696 specified. Very useful to increase past standard OS defaults on 697 high speed high latency (<em>i.e.</em>, 100ms or so, such as 698 transcontinental fast pipes).</p> 699 700 <p>If set to the value of <code>0</code>, the server will use the 701 OS default.</p> 702 703 <p>Further configuration of your operating system may be required to elicit 704 better performance on high speed, high latency connections.</p> 705 706 <div class="note"> <p> On some operating systems, changes in TCP behavior resulting 707 from a larger <code class="directive">SendBufferSize</code> may not be seen unless 708 <code class="directive"><a href="/mod/core.html#enablesendfile">EnableSendfile</a></code> is set to OFF. This 709 interaction applies only to static files.</p> </div> 710 711 712</div> 713<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 714<div class="directive-section"><h2><a name="ServerLimit" id="ServerLimit">ServerLimit</a> <a name="serverlimit" id="serverlimit">Directive</a></h2> 715<table class="directive"> 716<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Upper limit on configurable number of processes</td></tr> 717<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerLimit <var>number</var></code></td></tr> 718<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr> 719<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 720<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 721<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 722</table> 723 <p>For the <code class="module"><a href="/mod/prefork.html">prefork</a></code> MPM, this directive sets the 724 maximum configured value for <code class="directive"><a href="#maxclients">MaxClients</a></code> for the lifetime of the 725 Apache process. For the <code class="module"><a href="/mod/worker.html">worker</a></code> MPM, this directive 726 in combination with <code class="directive"><a href="#threadlimit">ThreadLimit</a></code> sets 727 the maximum configured value for <code class="directive"><a href="#maxclients">MaxClients</a></code> for the lifetime of the 728 Apache process. Any attempts to change this directive during a 729 restart will be ignored, but <code class="directive"><a href="#maxclients">MaxClients</a></code> can be modified during 730 a restart.</p> 731 732 <p>Special care must be taken when using this directive. If 733 <code class="directive">ServerLimit</code> is set to a value much higher 734 than necessary, extra, unused shared memory will be allocated. If 735 both <code class="directive">ServerLimit</code> and <code class="directive"><a href="#maxclients">MaxClients</a></code> are set to values 736 higher than the system can handle, Apache may not start or the 737 system may become unstable.</p> 738 739 <p>With the <code class="module"><a href="/mod/prefork.html">prefork</a></code> MPM, use this directive only 740 if you need to set <code class="directive"><a href="#maxclients">MaxClients</a></code> higher than 256 (default). 741 Do not set the value of this directive any higher than what you 742 might want to set <code class="directive"><a href="#maxclients">MaxClients</a></code> to.</p> 743 744 <p>With <code class="module"><a href="/mod/worker.html">worker</a></code> 745 use this directive only 746 if your <code class="directive"><a href="#maxclients">MaxClients</a></code> and 747 <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> 748 settings require more than 16 server processes (default). Do not set 749 the value of this directive any higher than the number of server 750 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> 751 752 <div class="note"><h3>Note</h3> 753 <p>There is a hard limit of <code>ServerLimit 20000</code> compiled 754 into the server (for the <code class="module"><a href="/mod/prefork.html">prefork</a></code> MPM 200000). This is 755 intended to avoid nasty effects caused by typos.</p> 756 </div> 757 758<h3>See also</h3> 759<ul> 760<li><a href="/stopping.html">Stopping and Restarting Apache</a></li> 761</ul> 762</div> 763<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 764<div class="directive-section"><h2><a name="StartServers" id="StartServers">StartServers</a> <a name="startservers" id="startservers">Directive</a></h2> 765<table class="directive"> 766<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of child server processes created at startup</td></tr> 767<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartServers <var>number</var></code></td></tr> 768<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr> 769<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 770<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 771<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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/worker.html">worker</a></code></td></tr> 772</table> 773 <p>The <code class="directive">StartServers</code> directive sets the 774 number of child server processes created on startup. As the number 775 of processes is dynamically controlled depending on the load, 776 there is usually little reason to adjust this parameter.</p> 777 778 <p>The default value differs from MPM to MPM. For 779 <code class="module"><a href="/mod/worker.html">worker</a></code> the default is <code>StartServers 3</code>. 780 For <code class="module"><a href="/mod/prefork.html">prefork</a></code> defaults to <code>5</code> and for 781 <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code> to <code>2</code>.</p> 782 783</div> 784<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 785<div class="directive-section"><h2><a name="StartThreads" id="StartThreads">StartThreads</a> <a name="startthreads" id="startthreads">Directive</a></h2> 786<table class="directive"> 787<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created on startup</td></tr> 788<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartThreads <var>number</var></code></td></tr> 789<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr> 790<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 791<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 792<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></td></tr> 793</table> 794 <p>Number of threads created on startup. As the 795 number of threads is dynamically controlled depending on the 796 load, there is usually little reason to adjust this 797 parameter.</p> 798 799 <p>For <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code> the default is 800 <code>StartThreads 50</code> and, since there is only a single 801 process, this is the total number of threads created at startup to 802 serve requests.</p> 803 804 <p>For <code class="module"><a href="/mod/beos.html">beos</a></code> the default is <code>StartThreads 805 10</code>. It also reflects the total number of threads created 806 at startup to serve requests.</p> 807 808</div> 809<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 810<div class="directive-section"><h2><a name="ThreadLimit" id="ThreadLimit">ThreadLimit</a> <a name="threadlimit" id="threadlimit">Directive</a></h2> 811<table class="directive"> 812<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the upper limit on the configurable number of threads 813per child process</td></tr> 814<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadLimit <var>number</var></code></td></tr> 815<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr> 816<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 817<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 818<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 819<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 820and later</td></tr> 821</table> 822 <p>This directive sets the maximum configured value for <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the lifetime 823 of the Apache process. Any attempts to change this directive 824 during a restart will be ignored, but <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> can be modified 825 during a restart up to the value of this directive.</p> 826 827 <p>Special care must be taken when using this directive. If 828 <code class="directive">ThreadLimit</code> is set to a value much higher 829 than <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>, 830 extra unused shared memory will be allocated. If both 831 <code class="directive">ThreadLimit</code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> are set to values 832 higher than the system can handle, Apache may not start or the 833 system may become unstable. Do not set the value of this directive 834 any higher than your greatest predicted setting of <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the 835 current run of Apache.</p> 836 837 <p>The default value for <code class="directive">ThreadLimit</code> is 838 <code>1920</code> when used with <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code> and 839 <code>64</code> when used with the others.</p> 840 841 <div class="note"><h3>Note</h3> 842 <p>There is a hard limit of <code>ThreadLimit 20000</code> (or 843 <code>ThreadLimit 15000</code> with <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>) 844 compiled into the server. This is intended to avoid nasty effects 845 caused by typos.</p> 846 </div> 847 848</div> 849<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 850<div class="directive-section"><h2><a name="ThreadsPerChild" id="ThreadsPerChild">ThreadsPerChild</a> <a name="threadsperchild" id="threadsperchild">Directive</a></h2> 851<table class="directive"> 852<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created by each child process</td></tr> 853<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadsPerChild <var>number</var></code></td></tr> 854<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr> 855<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 856<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 857<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 858</table> 859 <p>This directive sets the number of threads created by each 860 child process. The child creates these threads at startup and 861 never creates more. If using an MPM like <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>, 862 where there is only one child process, this number should be high 863 enough to handle the entire load of the server. If using an MPM 864 like <code class="module"><a href="/mod/worker.html">worker</a></code>, where there are multiple child processes, 865 the <em>total</em> number of threads should be high enough to handle 866 the common load on the server.</p> 867 868 <p>The default value for <code class="directive">ThreadsPerChild</code> is 869 <code>64</code> when used with <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code> and 870 <code>25</code> when used with the others.</p> 871 872</div> 873<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 874<div class="directive-section"><h2><a name="ThreadStackSize" id="ThreadStackSize">ThreadStackSize</a> <a name="threadstacksize" id="threadstacksize">Directive</a></h2> 875<table class="directive"> 876<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The size in bytes of the stack used by threads handling 877client connections</td></tr> 878<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadStackSize <var>size</var></code></td></tr> 879<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>65536 on NetWare; varies on other operating systems</code></td></tr> 880<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 881<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 882<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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/worker.html">worker</a></code>, <code class="module"><a href="/mod/event.html">event</a></code></td></tr> 883<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.1 and later</td></tr> 884</table> 885 <p>The <code class="directive">ThreadStackSize</code> directive sets the 886 size of the stack (for autodata) of threads which handle client 887 connections and call modules to help process those connections. 888 In most cases the operating system default for stack size is 889 reasonable, but there are some conditions where it may need to be 890 adjusted:</p> 891 892 <ul> 893 <li>On platforms with a relatively small default thread stack size 894 (e.g., HP-UX), Apache may crash when using some third-party modules 895 which use a relatively large amount of autodata storage. Those 896 same modules may have worked fine on other platforms where the 897 default thread stack size is larger. This type of crash is 898 resolved by setting <code class="directive">ThreadStackSize</code> to a 899 value higher than the operating system default. This type of 900 adjustment is necessary only if the provider of the third-party 901 module specifies that it is required, or if diagnosis of an Apache 902 crash indicates that the thread stack size was too small.</li> 903 904 <li>On platforms where the default thread stack size is 905 significantly larger than necessary for the web server 906 configuration, a higher number of threads per child process 907 will be achievable if <code class="directive">ThreadStackSize</code> is 908 set to a value lower than the operating system default. This type 909 of adjustment should only be made in a test environment which allows 910 the full set of web server processing can be exercised, as there 911 may be infrequent requests which require more stack to process. 912 The minimum required stack size strongly depends on the modules 913 used, but any change in the web server configuration can invalidate 914 the current <code class="directive">ThreadStackSize</code> setting.</li> 915 </ul> 916 917 <div class="note">It is recommended to not reduce <code class="directive">ThreadStackSize</code> 918 unless a high number of threads per child process is needed. On some 919 platforms (including Linux), a setting of 128000 is already too low and 920 causes crashes with some common modules.</div> 921 922</div> 923<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 924<div class="directive-section"><h2><a name="User" id="User">User</a> <a name="user" id="user">Directive</a></h2> 925<table class="directive"> 926<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The userid under which the server will answer 927requests</td></tr> 928<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>User <var>unix-userid</var></code></td></tr> 929<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>User #-1</code></td></tr> 930<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 931<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 932<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr> 933<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only valid in global server config since Apache 9342.0</td></tr> 935</table> 936 <p>The <code class="directive">User</code> directive sets the user ID as 937 which the server will answer requests. In order to use this 938 directive, the server must be run initially as <code>root</code>. 939 If you start the server as a non-root user, it will fail to change 940 to the lesser privileged user, and will instead continue to run as 941 that original user. If you do start the server as <code>root</code>, 942 then it is normal for the parent process to remain running as root. 943 <var>Unix-userid</var> is one of:</p> 944 945 <dl> 946 <dt>A username</dt> 947 <dd>Refers to the given user by name.</dd> 948 949 <dt># followed by a user number.</dt> 950 <dd>Refers to a user by its number.</dd> 951 </dl> 952 953 <p>The user should have no privileges that result in it being 954 able to access files that are not intended to be visible to the 955 outside world, and similarly, the user should not be able to 956 execute code that is not meant for HTTP requests. It is 957 recommended that you set up a new user and group specifically for 958 running the server. Some admins use user <code>nobody</code>, but 959 this is not always desirable, since the <code>nobody</code> user 960 can have other uses on the system.</p> 961 962 <div class="warning"><h3>Security</h3> 963 <p>Don't set <code class="directive">User</code> (or <code class="directive"><a href="#group">Group</a></code>) to <code>root</code> unless 964 you know exactly what you are doing, and what the dangers are.</p> 965 </div> 966 967 <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 968 configure your server for <code class="program"><a href="/programs/suexec.html">suexec</a></code> use 969 <code class="directive"><a href="/mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>.</p> 970 971 <div class="note"><h3>Note</h3> 972 <p>Although the <code class="directive">User</code> directive is present 973 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, 974 it is actually a no-op there and only exists for compatibility 975 reasons.</p> 976 </div> 977 978</div> 979</div> 980<div class="bottomlang"> 981<p><span>Available Languages: </span><a href="/de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | 982<a href="/en/mod/mpm_common.html" title="English"> en </a> | 983<a href="/ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 984<a href="/tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p> 985</div><div class="top"><a href="#page-header"><img src="/images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. 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