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<title>Apache Server Virtual Host Support</title>
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<h3>Apache HTTP Server Version 1.3</h3>
</div>
<h1 align="CENTER">File Descriptor Limits</h1>
<p>When using a large number of Virtual Hosts, Apache may run
out of available file descriptors (sometimes called <cite>file
handles</cite> if each Virtual Host specifies different log
files. The total number of file descriptors used by Apache is
one for each distinct error log file, one for every other log
file directive, plus 10-20 for internal use. Unix operating
systems limit the number of file descriptors that may be used
by a process; the limit is typically 64, and may usually be
increased up to a large hard-limit.</p>
<p>Although Apache attempts to increase the limit as required,
this may not work if:</p>
<ol>
<li>Your system does not provide the setrlimit() system
call.</li>
<li>The setrlimit(RLIMIT_NOFILE) call does not function on
your system (such as Solaris 2.3)</li>
<li>The number of file descriptors required exceeds the hard
limit.</li>
<li>Your system imposes other limits on file descriptors,
such as a limit on stdio streams only using file descriptors
below 256. (Solaris 2)</li>
</ol>
In the event of problems you can:
<ul>
<li>Reduce the number of log files; don't specify log files
in the VirtualHost sections, but only log to the main log
files.</li>
<li>
If you system falls into 1 or 2 (above), then increase the
file descriptor limit before starting Apache, using a
script like
<blockquote>
<code>#!/bin/sh<br />
ulimit -S -n 100<br />
exec httpd</code>
</blockquote>
</li>
</ul>
<p>Please see the <a
href="../misc/descriptors.html">Descriptors and Apache</a>
document containing further details about file descriptor
problems and how they can be solved on your operating
system.</p>
<hr />
<h3 align="CENTER">Apache HTTP Server Version 1.3</h3>
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