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15 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
16 <p class="apache">Apache HTTP Server Version 2.1</p>
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20 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.1</a> > <a href="./">Modules</a></div>
21 <div id="page-content">
22 <div id="preamble"><h1>Apache MPM Common Directives</h1>
24 <p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
25 <a href="../en/mod/mpm_common.html" title="English"> en </a> |
26 <a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
28 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A collection of directives that are implemented by
29 more than one multi-processing module (MPM)</td></tr>
30 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr></table>
32 <div id="quickview"><h3 class="directives">Directives</h3>
34 <li><img alt="" src="../images/down.gif" /> <a href="#acceptmutex">AcceptMutex</a></li>
35 <li><img alt="" src="../images/down.gif" /> <a href="#coredumpdirectory">CoreDumpDirectory</a></li>
36 <li><img alt="" src="../images/down.gif" /> <a href="#enableexceptionhook">EnableExceptionHook</a></li>
37 <li><img alt="" src="../images/down.gif" /> <a href="#group">Group</a></li>
38 <li><img alt="" src="../images/down.gif" /> <a href="#listen">Listen</a></li>
39 <li><img alt="" src="../images/down.gif" /> <a href="#listenbacklog">ListenBackLog</a></li>
40 <li><img alt="" src="../images/down.gif" /> <a href="#lockfile">LockFile</a></li>
41 <li><img alt="" src="../images/down.gif" /> <a href="#maxclients">MaxClients</a></li>
42 <li><img alt="" src="../images/down.gif" /> <a href="#maxmemfree">MaxMemFree</a></li>
43 <li><img alt="" src="../images/down.gif" /> <a href="#maxrequestsperchild">MaxRequestsPerChild</a></li>
44 <li><img alt="" src="../images/down.gif" /> <a href="#maxsparethreads">MaxSpareThreads</a></li>
45 <li><img alt="" src="../images/down.gif" /> <a href="#minsparethreads">MinSpareThreads</a></li>
46 <li><img alt="" src="../images/down.gif" /> <a href="#pidfile">PidFile</a></li>
47 <li><img alt="" src="../images/down.gif" /> <a href="#scoreboardfile">ScoreBoardFile</a></li>
48 <li><img alt="" src="../images/down.gif" /> <a href="#sendbuffersize">SendBufferSize</a></li>
49 <li><img alt="" src="../images/down.gif" /> <a href="#serverlimit">ServerLimit</a></li>
50 <li><img alt="" src="../images/down.gif" /> <a href="#startservers">StartServers</a></li>
51 <li><img alt="" src="../images/down.gif" /> <a href="#startthreads">StartThreads</a></li>
52 <li><img alt="" src="../images/down.gif" /> <a href="#threadlimit">ThreadLimit</a></li>
53 <li><img alt="" src="../images/down.gif" /> <a href="#threadsperchild">ThreadsPerChild</a></li>
54 <li><img alt="" src="../images/down.gif" /> <a href="#threadstacksize">ThreadStackSize</a></li>
55 <li><img alt="" src="../images/down.gif" /> <a href="#user">User</a></li>
59 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
60 <div class="directive-section"><h2><a name="AcceptMutex" id="AcceptMutex">AcceptMutex</a> <a name="acceptmutex" id="acceptmutex">Directive</a></h2>
61 <table class="directive">
62 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Method that Apache uses to serialize multiple children
63 accepting requests on network sockets</td></tr>
64 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AcceptMutex Default|<var>method</var></code></td></tr>
65 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AcceptMutex Default</code></td></tr>
66 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
67 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
68 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
70 <p>The <code class="directive">AcceptMutex</code> directives sets the
71 method that Apache uses to serialize multiple children accepting
72 requests on network sockets. Prior to Apache 2.0, the method was
73 selectable only at compile time. The optimal method to use is
74 highly architecture and platform dependent. For further details,
75 see the <a href="../misc/perf-tuning.html">performance tuning</a>
78 <p>If this directive is set to <code>Default</code>, then the
79 compile-time selected default will be used. Other possible
80 methods are listed below. Note that not all methods are
81 available on all platforms. If a method is specified which is
82 not available, a message will be written to the error log
83 listing the available methods.</p>
86 <dt><code>flock</code></dt>
87 <dd>uses the <code>flock(2)</code> system call to lock the
88 file defined by the <code class="directive"><a href="#lockfile">LockFile</a></code> directive.</dd>
90 <dt><code>fcntl</code></dt>
91 <dd>uses the <code>fcntl(2)</code> system call to lock the
92 file defined by the <code class="directive"><a href="#lockfile">LockFile</a></code> directive.</dd>
94 <dt><code>posixsem</code></dt>
95 <dd>uses POSIX compatible semaphores to implement the mutex.</dd>
97 <dt><code>pthread</code></dt>
98 <dd>uses POSIX mutexes as implemented by the POSIX Threads
99 (PThreads) specification.</dd>
101 <dt><code>sysvsem</code></dt>
102 <dd>uses SySV-style semaphores to implement the mutex.</dd>
105 <p>If you want to find out the compile time chosen default
106 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>
108 <div class="warning"><h3>Warning</h3>
109 <p>On most systems, when the <code>pthread</code> option
110 is selected, if a child process terminates abnormally
111 while holding the <code>AcceptCntl</code> mutex the
112 server will stop responding to requests. When this
113 occurs, the server will require a manual restart to
115 <p>Solaris is a notable exception as it provides a
116 mechanism, used by Apache, which usually allows the
117 mutex to be recovered after a child process terminates
118 abnormally while holding a mutex.</p>
119 <p>If your system implements the
120 <code>pthread_mutexattr_setrobust_np()</code> function,
121 you may be able to use the <code>pthread</code> option safely.</p>
125 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
126 <div class="directive-section"><h2><a name="CoreDumpDirectory" id="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory" id="coredumpdirectory">Directive</a></h2>
127 <table class="directive">
128 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory where Apache attempts to
129 switch before dumping core</td></tr>
130 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CoreDumpDirectory <var>directory</var></code></td></tr>
131 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for the default setting</code></td></tr>
132 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
133 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
134 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
136 <p>This controls the directory to which Apache attempts to
137 switch before dumping core. The default is in the
138 <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code> directory, however
139 since this should not be writable by the user the server runs
140 as, core dumps won't normally get written. If you want a core
141 dump for debugging, you can use this directive to place it in a
142 different location.</p>
144 <div class="note"><h3>Core Dumps on Linux</h3>
145 <p>If Apache starts as root and switches to another user, the
146 Linux kernel <em>disables</em> core dumps even if the directory is
147 writable for the process. Apache (2.0.46 and later) reenables core dumps
148 on Linux 2.4 and beyond, but only if you explicitly configure a <code class="directive">CoreDumpDirectory</code>.</p>
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="EnableExceptionHook" id="EnableExceptionHook">EnableExceptionHook</a> <a name="enableexceptionhook" id="enableexceptionhook">Directive</a></h2>
154 <table class="directive">
155 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a hook that runs exception handlers
156 after a crash</td></tr>
157 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableExceptionHook On|Off</code></td></tr>
158 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableExceptionHook Off</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/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
162 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.49 and later</td></tr>
164 <p>For safety reasons this directive is only available if the server was
165 configured with the <code>--enable-exception-hook</code> option. It
166 enables a hook that allows external modules to plug in and do something
167 after a child crashed.</p>
169 <p>There are already two modules, <code>mod_whatkilledus</code> and
170 <code>mod_backtrace</code> that make use of this hook. Please have a
171 look at Jeff Trawick's <a href="http://www.apache.org/~trawick/exception_hook.html">EnableExceptionHook site</a> for more information about these.</p>
174 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
175 <div class="directive-section"><h2><a name="Group" id="Group">Group</a> <a name="group" id="group">Directive</a></h2>
176 <table class="directive">
177 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Group under which the server will answer
179 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Group <var>unix-group</var></code></td></tr>
180 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Group #-1</code></td></tr>
181 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
182 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
183 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
184 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only valid in global server config since Apache
187 <p>The <code class="directive">Group</code> directive sets the group under
188 which the server will answer requests. In order to use this
189 directive, the server must be run initially as <code>root</code>. If
190 you start the server as a non-root user, it will fail to change to the
191 specified group, and will instead continue to run as the group of the
192 original user. <var>Unix-group</var> is one of:</p>
195 <dt>A group name</dt>
196 <dd>Refers to the given group by name.</dd>
198 <dt><code>#</code> followed by a group number.</dt>
199 <dd>Refers to a group by its number.</dd>
202 <div class="example"><h3>Example</h3><p><code>
206 <p>It is recommended that you set up a new group specifically for
207 running the server. Some admins use user <code>nobody</code>,
208 but this is not always possible or desirable.</p>
210 <div class="warning"><h3>Security</h3>
211 <p>Don't set <code class="directive">Group</code> (or <code class="directive"><a href="#user">User</a></code>) to <code>root</code> unless
212 you know exactly what you are doing, and what the dangers are.</p>
215 <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
216 configure your server for <a href="mod_suexec.html">suexec</a> use
217 <code class="directive"><a href="../mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>.</p>
219 <div class="note"><h3>Note</h3>
220 <p>Although the <code class="directive">Group</code> directive is present
221 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,
222 it is actually a no-op there and only exists for compatibility
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="Listen" id="Listen">Listen</a> <a name="listen" id="listen">Directive</a></h2>
229 <table class="directive">
230 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>IP addresses and ports that the server
232 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Listen [<var>IP-address</var>:]<var>portnumber</var></code></td></tr>
233 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
234 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
235 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
236 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Required directive since Apache 2.0</td></tr>
238 <p>The <code class="directive">Listen</code> directive instructs Apache to
239 listen to only specific IP addresses or ports; by default it
240 responds to requests on all IP interfaces. <code class="directive">Listen</code>
241 is now a required directive. If it is not in the config file, the
242 server will fail to start. This is a change from previous versions
245 <p>The <code class="directive">Listen</code> directive tells the server to
246 accept incoming requests on the specified port or address-and-port
247 combination. If only a port number is specified, the server listens to
248 the given port on all interfaces. If an IP address is given as well
249 as a port, the server will listen on the given port and
252 <p>Multiple <code class="directive">Listen</code> directives may be used to
253 specify a number of addresses and ports to listen to. The server will
254 respond to requests from any of the listed addresses and ports.</p>
256 <p>For example, to make the server accept connections on both
257 port 80 and port 8000, use:</p>
259 <div class="example"><p><code>
264 <p>To make the server accept connections on two specified
265 interfaces and port numbers, use </p>
267 <div class="example"><p><code>
268 Listen 192.170.2.1:80<br />
269 Listen 192.170.2.5:8000
272 <p>IPv6 addresses must be surrounded in square brackets, as in the
273 following example:</p>
275 <div class="example"><p><code>
276 Listen [fe80::a00:20ff:fea7:ccea]:80
281 <li><a href="../dns-caveats.html">DNS Issues</a></li>
282 <li><a href="../bind.html">Setting which addresses and ports Apache
286 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
287 <div class="directive-section"><h2><a name="ListenBackLog" id="ListenBackLog">ListenBackLog</a> <a name="listenbacklog" id="listenbacklog">Directive</a></h2>
288 <table class="directive">
289 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum length of the queue of pending connections</td></tr>
290 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenBacklog <var>backlog</var></code></td></tr>
291 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenBacklog 511</code></td></tr>
292 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
293 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
294 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
296 <p>The maximum length of the queue of pending connections.
297 Generally no tuning is needed or desired, however on some
298 systems it is desirable to increase this when under a TCP SYN
299 flood attack. See the backlog parameter to the
300 <code>listen(2)</code> system call.</p>
302 <p>This will often be limited to a smaller number by the
303 operating system. This varies from OS to OS. Also note that
304 many OSes do not use exactly what is specified as the backlog,
305 but use a number based on (but normally larger than) what is
309 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
310 <div class="directive-section"><h2><a name="LockFile" id="LockFile">LockFile</a> <a name="lockfile" id="lockfile">Directive</a></h2>
311 <table class="directive">
312 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the accept serialization lock file</td></tr>
313 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LockFile <var>filename</var></code></td></tr>
314 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LockFile logs/accept.lock</code></td></tr>
315 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
316 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
317 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
319 <p>The <code class="directive">LockFile</code> directive sets the path to
320 the lockfile used when Apache is used with an <code class="directive"><a href="#acceptmutex">AcceptMutex</a></code> value of either
321 <code>fcntl</code> or <code>flock</code>. This directive should
322 normally be left at its default value. The main reason for changing
323 it is if the <code>logs</code> directory is NFS mounted, since
324 <strong>the lockfile must be stored on a local disk</strong>. The PID
325 of the main server process is automatically appended to the
328 <div class="warning"><h3>Security</h3>
329 <p>It is best to <em>avoid</em> putting this file in a world writable
330 directory such as <code>/var/tmp</code> because someone could create
331 a denial of service attack and prevent the server from starting by
332 creating a lockfile with the same name as the one the server will try
338 <li><code class="directive"><a href="#acceptmutex">AcceptMutex</a></code></li>
341 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
342 <div class="directive-section"><h2><a name="MaxClients" id="MaxClients">MaxClients</a> <a name="maxclients" id="maxclients">Directive</a></h2>
343 <table class="directive">
344 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of child processes that will be created
345 to serve requests</td></tr>
346 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxClients <var>number</var></code></td></tr>
347 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
348 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
349 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
350 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
352 <p>The <code class="directive">MaxClients</code> directive sets the limit
353 on the number of simultaneous requests that will be served. Any
354 connection attempts over the <code class="directive">MaxClients</code>
355 limit will normally be queued, up to a number based on the
356 <code class="directive"><a href="#listenbacklog">ListenBacklog</a></code>
357 directive. Once a child process is freed at the end of a different
358 request, the connection will then be serviced.</p>
360 <p>For non-threaded servers (<em>i.e.</em>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>),
361 <code class="directive">MaxClients</code> translates into the maximum
362 number of child processes that will be launched to serve requests.
363 The default value is <code>256</code>; to increase it, you must also raise
364 <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
366 <p>For threaded and hybrid servers (<em>e.g.</em> <code class="module"><a href="../mod/beos.html">beos</a></code>
367 or <code class="module"><a href="../mod/worker.html">worker</a></code>) <code class="directive">MaxClients</code> restricts
368 the total number of threads that will be available to serve clients.
369 The default value for <code class="module"><a href="../mod/beos.html">beos</a></code> is <code>50</code>. For
370 hybrid MPMs the default value is <code>16</code> (<code class="directive"><a href="#serverlimit">ServerLimit</a></code>) multiplied by the value of
371 <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,
372 you must also raise <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
375 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
376 <div class="directive-section"><h2><a name="MaxMemFree" id="MaxMemFree">MaxMemFree</a> <a name="maxmemfree" id="maxmemfree">Directive</a></h2>
377 <table class="directive">
378 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of memory that the main allocator is allowed
379 to hold without calling free()</td></tr>
380 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxMemFree <var>KBytes</var></code></td></tr>
381 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxMemFree 0</code></td></tr>
382 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
383 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
384 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code></td></tr>
386 <p>The <code class="directive">MaxMemFree</code> directive sets the
387 maximum number of free Kbytes that the main allocator is allowed
388 to hold without calling <code>free()</code>. When not set, or when set
389 to zero, the threshold will be set to unlimited.</p>
392 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
393 <div class="directive-section"><h2><a name="MaxRequestsPerChild" id="MaxRequestsPerChild">MaxRequestsPerChild</a> <a name="maxrequestsperchild" id="maxrequestsperchild">Directive</a></h2>
394 <table class="directive">
395 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on the number of requests that an individual child server
396 will handle during its life</td></tr>
397 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRequestsPerChild <var>number</var></code></td></tr>
398 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxRequestsPerChild 10000</code></td></tr>
399 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
400 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
401 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
403 <p>The <code class="directive">MaxRequestsPerChild</code> directive sets
404 the limit on the number of requests that an individual child
405 server process will handle. After
406 <code class="directive">MaxRequestsPerChild</code> requests, the child
407 process will die. If <code class="directive">MaxRequestsPerChild</code> is
408 <code>0</code>, then the process will never expire.</p>
410 <div class="note"><h3>Different default values</h3>
411 <p>The default value for <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> and
412 <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> is <code>0</code>.</p>
415 <p>Setting <code class="directive">MaxRequestsPerChild</code> to a
416 non-zero limit has two beneficial effects:</p>
419 <li>it limits the amount of memory that process can consume
420 by (accidental) memory leakage;</li>
422 <li>by giving processes a finite lifetime, it helps reduce
423 the number of processes when the server load reduces.</li>
426 <div class="note"><h3>Note</h3>
427 <p>For <code class="directive"><a href="../mod/core.html#keepalive">KeepAlive</a></code> requests, only
428 the first request is counted towards this limit. In effect, it
429 changes the behavior to limit the number of <em>connections</em> per
434 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
435 <div class="directive-section"><h2><a name="MaxSpareThreads" id="MaxSpareThreads">MaxSpareThreads</a> <a name="maxsparethreads" id="maxsparethreads">Directive</a></h2>
436 <table class="directive">
437 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle threads</td></tr>
438 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareThreads <var>number</var></code></td></tr>
439 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
440 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
441 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
442 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
444 <p>Maximum number of idle threads. Different MPMs deal with this
445 directive differently.</p>
447 <p>For <code class="module"><a href="../mod/perchild.html">perchild</a></code> the default is
448 <code>MaxSpareThreads 10</code>. This MPM monitors the number of
449 idle threads on a per-child basis. If there are too many idle
450 threads in that child, the server will begin to kill threads
451 within that child.</p>
453 <p>For <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code> and <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> the default is <code>MaxSpareThreads 250</code>.
454 These MPMs deal with idle threads on a server-wide basis. If there
455 are too many idle threads in the server then child processes are
456 killed until the number of idle threads is less than this number.</p>
458 <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
459 <code>MaxSpareThreads 100</code>. Since this MPM runs a
460 single-process, the spare thread count is also server-wide.</p>
462 <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
463 similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. The default for
464 <code class="module"><a href="../mod/beos.html">beos</a></code> is <code>MaxSpareThreads 50</code>. For
465 <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>10</code>.</p>
467 <div class="note"><h3>Restrictions</h3>
468 <p>The range of the <code class="directive">MaxSpareThreads</code> value
469 is restricted. Apache will correct the given value automatically
470 according to the following rules:</p>
472 <li><code class="module"><a href="../mod/perchild.html">perchild</a></code> requires <code class="directive">MaxSpareThreads</code> to be less or equal than <code class="directive"><a href="#threadlimit">ThreadLimit</a></code>.</li>
474 <li><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> wants the value to be greater than
475 <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>.</li>
477 <li>For <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> and
478 <code class="module"><a href="../mod/worker.html">worker</a></code> the value must be greater or equal than
479 the sum of <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>
480 and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</li>
486 <li><code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code></li>
487 <li><code class="directive"><a href="#startservers">StartServers</a></code></li>
490 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
491 <div class="directive-section"><h2><a name="MinSpareThreads" id="MinSpareThreads">MinSpareThreads</a> <a name="minsparethreads" id="minsparethreads">Directive</a></h2>
492 <table class="directive">
493 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle threads available to handle request
495 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareThreads <var>number</var></code></td></tr>
496 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
497 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
498 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
499 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
501 <p>Minimum number of idle threads to handle request spikes.
502 Different MPMs deal with this directive
505 <p><code class="module"><a href="../mod/perchild.html">perchild</a></code> uses a default of
506 <code>MinSpareThreads 5</code> and monitors the number of idle
507 threads on a per-child basis. If there aren't enough idle threads
508 in that child, the server will begin to create new threads within
509 that child. Thus, if you set <code class="directive"><a href="../mod/perchild.html#numservers">NumServers</a></code> to <code>10</code> and a <code class="directive">MinSpareThreads</code> value of <code>5</code>, you'll have
510 at least 50 idle threads on your system.</p>
512 <p><code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code> and
513 <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> use a default of <code>MinSpareThreads
514 75</code> and deal with idle threads on a server-wide basis. If
515 there aren't enough idle threads in the server then child
516 processes are created until the number of idle threads is greater
519 <p><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> uses a default of
520 <code>MinSpareThreads 10</code> and, since it is a single-process
521 MPM, tracks this on a server-wide bases.</p>
523 <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
524 similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. The default for
525 <code class="module"><a href="../mod/beos.html">beos</a></code> is <code>MinSpareThreads 1</code>. For
526 <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>5</code>.</p>
530 <li><code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code></li>
531 <li><code class="directive"><a href="#startservers">StartServers</a></code></li>
534 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
535 <div class="directive-section"><h2><a name="PidFile" id="PidFile">PidFile</a> <a name="pidfile" id="pidfile">Directive</a></h2>
536 <table class="directive">
537 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File where the server records the process ID
538 of the daemon</td></tr>
539 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PidFile <var>filename</var></code></td></tr>
540 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>PidFile logs/httpd.pid</code></td></tr>
541 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
542 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
543 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
545 <p>The <code class="directive">PidFile</code> directive sets the file to
546 which the server records the process id of the daemon. If the
547 filename is not absolute then it is assumed to be relative to the
548 <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
550 <div class="example"><h3>Example</h3><p><code>
551 PidFile /var/run/apache.pid
554 <p>It is often useful to be able to send the server a signal,
555 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
556 re-reads its configuration files. This is done by sending a
557 SIGHUP (kill -1) signal to the process id listed in the
558 <code class="directive">PidFile</code>.</p>
560 <p>The <code class="directive">PidFile</code> is subject to the same
561 warnings about log file placement and <a href="../misc/security_tips.html#serverroot">security</a>.</p>
563 <div class="note"><h3>Note</h3>
564 <p>As of Apache 2 it is recommended to use only the <a href="../programs/apachectl.html">apachectl</a> script for
565 (re-)starting or stopping the server.</p>
569 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
570 <div class="directive-section"><h2><a name="ScoreBoardFile" id="ScoreBoardFile">ScoreBoardFile</a> <a name="scoreboardfile" id="scoreboardfile">Directive</a></h2>
571 <table class="directive">
572 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the file used to store coordination data for
573 the child processes</td></tr>
574 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScoreBoardFile <var>file-path</var></code></td></tr>
575 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScoreBoardFile logs/apache_status</code></td></tr>
576 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
577 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
578 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
580 <p>Apache uses a scoreboard to communicate between its parent
581 and child processes. Some architectures require a file to facilitate
582 this communication. If the file is left unspecified, Apache first
583 attempts to create the scoreboard entirely in memory (using anonymous
584 shared memory) and, failing that, will attempt to create the file on
585 disk (using file-based shared memory). Specifying this directive causes
586 Apache to always create the file on the disk.</p>
588 <div class="example"><h3>Example</h3><p><code>
589 ScoreBoardFile /var/run/apache_status
592 <p>File-based shared memory is useful for third-party applications
593 that require direct access to the scoreboard.</p>
595 <p>If you use a <code class="directive">ScoreBoardFile</code> then
596 you may see improved speed by placing it on a RAM disk. But be
597 careful that you heed the same warnings about log file placement
598 and <a href="../misc/security_tips.html">security</a>.</p>
602 <li><a href="../stopping.html">Stopping and Restarting
606 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
607 <div class="directive-section"><h2><a name="SendBufferSize" id="SendBufferSize">SendBufferSize</a> <a name="sendbuffersize" id="sendbuffersize">Directive</a></h2>
608 <table class="directive">
609 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP buffer size</td></tr>
610 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SendBufferSize <var>bytes</var></code></td></tr>
611 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SendBufferSize 0</code></td></tr>
612 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
613 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
614 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
616 <p>The server will set the TCP buffer size to the number of bytes
617 specified. Very useful to increase past standard OS defaults on
618 high speed high latency (<em>i.e.</em>, 100ms or so, such as
619 transcontinental fast pipes).</p>
621 <p>If set to the value of <code>0</code>, the server will use the
625 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
626 <div class="directive-section"><h2><a name="ServerLimit" id="ServerLimit">ServerLimit</a> <a name="serverlimit" id="serverlimit">Directive</a></h2>
627 <table class="directive">
628 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Upper limit on configurable number of processes</td></tr>
629 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerLimit <var>number</var></code></td></tr>
630 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
631 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
632 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
633 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
635 <p>For the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, this directive sets the
636 maximum configured value for <code class="directive"><a href="#maxclients">MaxClients</a></code> for the lifetime of the
637 Apache process. For the <code class="module"><a href="../mod/worker.html">worker</a></code> MPM, this directive
638 in combination with <code class="directive"><a href="#threadlimit">ThreadLimit</a></code> sets
639 the maximum configured value for <code class="directive"><a href="#maxclients">MaxClients</a></code> for the lifetime of the
640 Apache process. Any attempts to change this directive during a
641 restart will be ignored, but <code class="directive"><a href="#maxclients">MaxClients</a></code> can be modified during
644 <p>Special care must be taken when using this directive. If
645 <code class="directive">ServerLimit</code> is set to a value much higher
646 than necessary, extra, unused shared memory will be allocated. If
647 both <code class="directive">ServerLimit</code> and <code class="directive"><a href="#maxclients">MaxClients</a></code> are set to values
648 higher than the system can handle, Apache may not start or the
649 system may become unstable.</p>
651 <p>With the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, use this directive only
652 if you need to set <code class="directive"><a href="#maxclients">MaxClients</a></code> higher than 256 (default).
653 Do not set the value of this directive any higher than what you
654 might want to set <code class="directive"><a href="#maxclients">MaxClients</a></code> to.</p>
656 <p>With <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/leader.html">leader</a></code> and
657 <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> use this directive only
658 if your <code class="directive"><a href="#maxclients">MaxClients</a></code> and
659 <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>
660 settings require more than 16 server processes (default). Do not set
661 the value of this directive any higher than the number of server
662 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>
664 <p>With the <code class="module"><a href="../mod/perchild.html">perchild</a></code> MPM, use this directive only
665 if you need to set <code class="directive"><a href="../mod/perchild.html#numservers">NumServers</a></code> higher than 8 (default).</p>
667 <div class="note"><h3>Note</h3>
668 <p>There is a hard limit of <code>ServerLimit 20000</code> compiled
669 into the server (for the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM 200000). This is
670 intended to avoid nasty effects caused by typos.</p>
675 <li><a href="../stopping.html">Stopping and Restarting Apache</a></li>
678 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
679 <div class="directive-section"><h2><a name="StartServers" id="StartServers">StartServers</a> <a name="startservers" id="startservers">Directive</a></h2>
680 <table class="directive">
681 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of child server processes created at startup</td></tr>
682 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartServers <var>number</var></code></td></tr>
683 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
684 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
685 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
686 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
688 <p>The <code class="directive">StartServers</code> directive sets the
689 number of child server processes created on startup. As the number
690 of processes is dynamically controlled depending on the load,
691 there is usually little reason to adjust this parameter.</p>
693 <p>The default value differs from MPM to MPM. For
694 <code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code> and
695 <code class="module"><a href="../mod/worker.html">worker</a></code> the default is <code>StartServers 3</code>.
696 For <code class="module"><a href="../mod/prefork.html">prefork</a></code> defaults to <code>5</code> and for
697 <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> to <code>2</code>.</p>
700 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
701 <div class="directive-section"><h2><a name="StartThreads" id="StartThreads">StartThreads</a> <a name="startthreads" id="startthreads">Directive</a></h2>
702 <table class="directive">
703 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created on startup</td></tr>
704 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartThreads <var>number</var></code></td></tr>
705 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
706 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
707 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
708 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/beos.html">beos</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code></td></tr>
710 <p>Number of threads created on startup. As the
711 number of threads is dynamically controlled depending on the
712 load, there is usually little reason to adjust this
715 <p>For <code class="module"><a href="../mod/perchild.html">perchild</a></code> the default is <code>StartThreads
716 5</code> and this directive tracks the number of threads per
717 process at startup.</p>
719 <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
720 <code>StartThreads 50</code> and, since there is only a single
721 process, this is the total number of threads created at startup to
724 <p>For <code class="module"><a href="../mod/beos.html">beos</a></code> the default is <code>StartThreads
725 10</code>. It also reflects the total number of threads created
726 at startup to serve requests.</p>
729 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
730 <div class="directive-section"><h2><a name="ThreadLimit" id="ThreadLimit">ThreadLimit</a> <a name="threadlimit" id="threadlimit">Directive</a></h2>
731 <table class="directive">
732 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the upper limit on the configurable number of threads
733 per child process</td></tr>
734 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadLimit <var>number</var></code></td></tr>
735 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
736 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
737 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
738 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
739 <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
742 <p>This directive sets the maximum configured value for <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the lifetime
743 of the Apache process. Any attempts to change this directive
744 during a restart will be ignored, but <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> can be modified
745 during a restart up to the value of this directive.</p>
747 <p>Special care must be taken when using this directive. If
748 <code class="directive">ThreadLimit</code> is set to a value much higher
749 than <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>,
750 extra unused shared memory will be allocated. If both
751 <code class="directive">ThreadLimit</code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> are set to values
752 higher than the system can handle, Apache may not start or the
753 system may become unstable. Do not set the value of this directive
754 any higher than your greatest predicted setting of <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the
755 current run of Apache.</p>
757 <p>The default value for <code class="directive">ThreadLimit</code> is
758 <code>1920</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
759 <code>64</code> when used with the others.</p>
761 <div class="note"><h3>Note</h3>
762 <p>There is a hard limit of <code>ThreadLimit 20000</code> (or
763 <code>ThreadLimit 15000</code> with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>)
764 compiled into the server. This is intended to avoid nasty effects
769 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
770 <div class="directive-section"><h2><a name="ThreadsPerChild" id="ThreadsPerChild">ThreadsPerChild</a> <a name="threadsperchild" id="threadsperchild">Directive</a></h2>
771 <table class="directive">
772 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created by each child process</td></tr>
773 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadsPerChild <var>number</var></code></td></tr>
774 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
775 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
776 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
777 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
779 <p>This directive sets the number of threads created by each
780 child process. The child creates these threads at startup and
781 never creates more. If using an MPM like <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>,
782 where there is only one child process, this number should be high
783 enough to handle the entire load of the server. If using an MPM
784 like <code class="module"><a href="../mod/worker.html">worker</a></code>, where there are multiple child processes,
785 the <em>total</em> number of threads should be high enough to handle
786 the common load on the server.</p>
788 <p>The default value for <code class="directive">ThreadsPerChild</code> is
789 <code>64</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
790 <code>25</code> when used with the others.</p>
793 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
794 <div class="directive-section"><h2><a name="ThreadStackSize" id="ThreadStackSize">ThreadStackSize</a> <a name="threadstacksize" id="threadstacksize">Directive</a></h2>
795 <table class="directive">
796 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The size in bytes of the stack used by threads handling
797 client connections</td></tr>
798 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadStackSize <var>size</var></code></td></tr>
799 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>65536 on NetWare; varies on other operating systems</code></td></tr>
800 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
801 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
802 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
803 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.1 and later</td></tr>
805 <p>The <code class="directive">ThreadStackSize</code> directive sets the
806 size of the stack (for autodata) of threads which handle client
807 connections and call modules to help process those connections.
808 In most cases the operating system default for stack size is
809 reasonable, but there are some conditions where it may need to be
813 <li>On platforms with a relatively small default thread stack size
814 (e.g., HP-UX), Apache may crash when using some third-party modules
815 which use a relatively large amount of autodata storage. Those
816 same modules may have worked fine on other platforms where the
817 default thread stack size is larger. This type of crash is
818 resolved by setting <code class="directive">ThreadStackSize</code> to a
819 value higher than the operating system default. This type of
820 adjustment is necessary only if the provider of the third-party
821 module specifies that it is required, or if diagnosis of an Apache
822 crash indicates that the thread stack size was too small.</li>
824 <li>On platforms where the default thread stack size is
825 significantly larger than necessary for the web server
826 configuration, a higher number of threads per child process
827 will be achievable if <code class="directive">ThreadStackSize</code> is
828 set to a value lower than the operating system default. This type
829 of adjustment should only be made in a test environment which allows
830 the full set of web server processing can be exercised, as there
831 may be infrequent requests which require more stack to process.
832 A change in the web server configuration can invalidate the
833 current <code class="directive">ThreadStackSize</code> setting.</li>
837 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
838 <div class="directive-section"><h2><a name="User" id="User">User</a> <a name="user" id="user">Directive</a></h2>
839 <table class="directive">
840 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The userid under which the server will answer
842 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>User <var>unix-userid</var></code></td></tr>
843 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>User #-1</code></td></tr>
844 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
845 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
846 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/leader.html">leader</a></code>, <code class="module"><a href="../mod/perchild.html">perchild</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
847 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only valid in global server config since Apache
850 <p>The <code class="directive">User</code> directive sets the user ID as
851 which the server will answer requests. In order to use this
852 directive, the server must be run initially as <code>root</code>.
853 If you start the server as a non-root user, it will fail to change
854 to the lesser privileged user, and will instead continue to run as
855 that original user. If you do start the server as <code>root</code>,
856 then it is normal for the parent process to remain running as root.
857 <var>Unix-userid</var> is one of:</p>
861 <dd>Refers to the given user by name.</dd>
863 <dt># followed by a user number.</dt>
864 <dd>Refers to a user by its number.</dd>
867 <p>The user should have no privileges that result in it being
868 able to access files that are not intended to be visible to the
869 outside world, and similarly, the user should not be able to
870 execute code that is not meant for HTTP requests. It is
871 recommended that you set up a new user and group specifically for
872 running the server. Some admins use user <code>nobody</code>, but
873 this is not always desirable, since the <code>nobody</code> user
874 can have other uses on the system.</p>
876 <div class="warning"><h3>Security</h3>
877 <p>Don't set <code class="directive">User</code> (or <code class="directive"><a href="#group">Group</a></code>) to <code>root</code> unless
878 you know exactly what you are doing, and what the dangers are.</p>
881 <p>With the <code class="module"><a href="../mod/perchild.html">perchild</a></code> MPM, which is intended to
882 server virtual hosts run under different user IDs, the
883 <code class="directive">User</code> directive defines the user ID for the
884 main server and the fallback for <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> sections without an
885 <code class="directive"><a href="../mod/perchild.html#assignuserid">AssignUserID</a></code> directive.</p>
887 <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
888 configure your server for <a href="../suexec.html">suexec</a> use
889 <code class="directive"><a href="../mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>.</p>
891 <div class="note"><h3>Note</h3>
892 <p>Although the <code class="directive">User</code> directive is present
893 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,
894 it is actually a no-op there and only exists for compatibility
900 <div class="bottomlang">
901 <p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
902 <a href="../en/mod/mpm_common.html" title="English"> en </a> |
903 <a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
904 </div><div id="footer">
905 <p class="apache">Copyright 1999-2004 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
906 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>