docs/manual/invoking.xml

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<manualpage metafile="invoking.xml.meta">

  <title>Starting Apache</title>

<summary>
    <p>On Windows, Apache is normally run as a service.
    For details, see <a
    href="platform/windows.html#winsvc">Running Apache as a Service</a>.
    </p>

    <p>On Unix, the <program>httpd</program> program
    is run as a daemon that executes continuously in the
    background to handle requests.  This document describes how
    to invoke <program>httpd</program>.</p>
</summary>

<seealso><a href="stopping.html">Stopping and Restarting</a></seealso>
<seealso><program>httpd</program></seealso>
<seealso><program>apachectl</program></seealso>

<section id="startup"><title>How Apache Starts</title>

    <p>If the <directive module="mpm_common">Listen</directive>
    specified in the configuration file is default of 80 (or any other
    port below 1024), then it is necessary to have root privileges in
    order to start apache, so that it can bind to this privileged
    port. Once the server has started and performed a few preliminary
    activities such as opening its log files, it will launch several
    <em>child</em> processes which do the work of listening for and
    answering requests from clients. The main <code>httpd</code>
    process continues to run as the root user, but the child processes
    run as a less privileged user. This is controlled by the selected
    <a href="mpm.html">Multi-Processing Module</a>.</p>

    <p>The recommended method of invoking the <program>httpd</program>
    executable is to use the <program>apachectl</program> control script. This
    script sets certain environment variables that are necessary for
    <program>httpd</program> to function correctly under some operating
    systems, and then invokes the <program>httpd</program> binary.
    <program>apachectl</program> will pass through any command line
    arguments, so any <program>httpd</program> options may also be used with
    <program>apachectl</program>.  You may also directly edit the
    <program>apachectl</program> script by changing the <code>HTTPD</code>
    variable near the top to specify the correct location of the
    <program>httpd</program> binary and any command-line arguments that you
    wish to be <em>always</em> present.</p>

    <p>The first thing that <program>httpd</program> does when it is
    invoked is to locate and read the <a
    href="configuring.html">configuration file</a>
    <code>httpd.conf</code>. The location of this file is set at
    compile-time, but it is possible to specify its location at run
    time using the <code>-f</code> command-line option as in</p>

<example>/usr/local/apache2/bin/apachectl -f
      /usr/local/apache2/conf/httpd.conf</example>

    <p>If all goes well during startup, the server will detach from
    the terminal and the command prompt will return almost
    immediately. This indicates that the server is up and running.
    You can then use your browser to connect to the server and view
    the test page in the <directive
    module="core">DocumentRoot</directive> directory.</p>
</section>

<section id="errors"><title>Errors During Start-up</title>

    <p>If Apache suffers a fatal problem during startup, it will
    write a message describing the problem either to the console or
    to the <directive module="core">ErrorLog</directive> before
    exiting. One of the most common error messages is "<code>Unable
    to bind to Port ...</code>". This message is usually caused by
    either:</p>

    <ul>
      <li>Trying to start the server on a privileged port when not
      logged in as the root user; or</li>

      <li>Trying to start the server when there is another instance
      of Apache or some other web server already bound to the same
      Port.</li>
    </ul>

    <p>For further trouble-shooting instructions, consult the
    Apache <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a>.</p>
</section>

<section id="boot"><title>Starting at Boot-Time</title>

    <p>If you want your server to continue running after a system
    reboot, you should add a call to <program>apachectl</program> to your
    system startup files (typically <code>rc.local</code> or a file in
    an <code>rc.N</code> directory). This will start Apache as
    root. Before doing this ensure that your server is properly
    configured for security and access restrictions.</p>

    <p>The <program>apachectl</program> script is designed to act like a
    standard SysV init script; it can take the arguments
    <code>start</code>, <code>restart</code>, and <code>stop</code>
    and translate them into the appropriate signals to
    <program>httpd</program>.  So you can often simply link
    <program>apachectl</program> into the appropriate init directory. But be
    sure to check the exact requirements of your system.</p>
</section>

<section id="info"><title>Additional Information</title>

    <p>Additional information about the command-line options of <program>
    httpd</program> and <program>apachectl</program> as well as other support
    programs included with the server is available on the
    <a href="programs/">Server and Supporting Programs</a> page.
    There is also documentation on all the <a
    href="mod/">modules</a> included with the Apache distribution
    and the <a href="mod/directives.html">directives</a> that they
    provide.</p>
</section>

</manualpage>