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    <title>Apache Server Virtual Host Support</title>
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      <h3>Apache HTTP Server Version 1.3</h3>
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    <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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