docs/manual/vhosts/ip-based.html - httpd - Git at Google

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     <h1 align="CENTER">Apache IP-based Virtual Host Support</h1>
     <strong>See also:</strong> <a href="name-based.html">Name-based
     Virtual Hosts Support</a>
     <hr />

     <h2>System requirements</h2>
     As the term <cite>IP-based</cite> indicates, the server
     <strong>must have a different IP address for each IP-based
     virtual host</strong>. This can be achieved by the machine
     having several physical network connections, or by use of
     virtual interfaces which are supported by most modern operating
     systems (see system documentation for details, these are
     frequently called "ip aliases", and the "ifconfig" command is
     most commonly used to set them up).

     <h2>How to set up Apache</h2>
     There are two ways of configuring apache to support multiple
     hosts. Either by running a separate httpd daemon for each
     hostname, or by running a single daemon which supports all the
     virtual hosts.

     <p>Use multiple daemons when:</p>

     <ul>
       <li>There are security partitioning issues, such as company1
       does not want anyone at company2 to be able to read their
       data except via the web. In this case you would need two
       daemons, each running with different <a
       href="../mod/mpm_common.html#user">User</a>, <a
       href="../mod/mpm_common.html#group">Group</a>, <a
       href="../mod/mpm_common.html#listen">Listen</a>, and <a
       href="../mod/core.html#serverroot">ServerRoot</a>
       settings.</li>

       <li>You can afford the memory and <a
       href="../misc/descriptors.html">file descriptor
       requirements</a> of listening to every IP alias on the
       machine. It's only possible to <a
       href="../mod/mpm_common.html#listen">Listen</a> to the "wildcard"
       address, or to specific addresses. So if you have a need to
       listen to a specific address for whatever reason, then you
       will need to listen to all specific addresses. (Although one
       httpd could listen to N-1 of the addresses, and another could
       listen to the remaining address.)</li>
     </ul>
     Use a single daemon when:

     <ul>
       <li>Sharing of the httpd configuration between virtual hosts
       is acceptable.</li>

       <li>The machine services a large number of requests, and so
       the performance loss in running separate daemons may be
       significant.</li>
     </ul>

     <h2>Setting up multiple daemons</h2>
     Create a separate httpd installation for each virtual host. For
     each installation, use the <a
     href="../mod/mpm_common.html#listen">Listen</a> directive in the
     configuration file to select which IP address (or virtual host)
     that daemon services. e.g.
 <pre>
     Listen www.smallco.com:80
 </pre>
     It is recommended that you use an IP address instead of a
     hostname (see <a href="../dns-caveats.html">DNS caveats</a>).

     <h2>Setting up a single daemon with virtual hosts</h2>
     For this case, a single httpd will service requests for the
     main server and all the virtual hosts. The <a
     href="../mod/core.html#virtualhost">VirtualHost</a> directive
     in the configuration file is used to set the values of <a
     href="../mod/core.html#serveradmin">ServerAdmin</a>, <a
     href="../mod/core.html#servername">ServerName</a>, <a
     href="../mod/core.html#documentroot">DocumentRoot</a>, <a
     href="../mod/core.html#errorlog">ErrorLog</a> and <a
     href="../mod/mod_log_config.html#transferlog">TransferLog</a>
     or <a href="../mod/mod_log_config.html#customlog">CustomLog</a>
     configuration directives to different values for each virtual
     host. e.g.
 <pre>
     &lt;VirtualHost www.smallco.com&gt;
     ServerAdmin webmaster@mail.smallco.com
     DocumentRoot /groups/smallco/www
     ServerName www.smallco.com
     ErrorLog /groups/smallco/logs/error_log
     TransferLog /groups/smallco/logs/access_log
     &lt;/VirtualHost&gt;

     &lt;VirtualHost www.baygroup.org&gt;
     ServerAdmin webmaster@mail.baygroup.org
     DocumentRoot /groups/baygroup/www
     ServerName www.baygroup.org
     ErrorLog /groups/baygroup/logs/error_log
     TransferLog /groups/baygroup/logs/access_log
     &lt;/VirtualHost&gt;
 </pre>
     It is recommended that you use an IP address instead of a
     hostname (see <a href="../dns-caveats.html">DNS caveats</a>).

     <p>Almost <strong>any</strong> configuration directive can be
     put in the VirtualHost directive, with the exception of
     directives that control process creation and a few other
     directives. To find out if a directive can be used in the
     VirtualHost directive, check the <a
     href="../mod/directive-dict.html#Context">Context</a> using the
     <a href="../mod/directives.html">directive index</a>.</p>

     <p><a href="../mod/mpm_common.html#user">User</a> and <a
     href="../mod/mpm_common.html#group">Group</a> may be used inside a
     VirtualHost directive if the <a href="../suexec.html">suEXEC
     wrapper</a> is used.</p>

     <p><em>SECURITY:</em> When specifying where to write log files,
     be aware of some security risks which are present if anyone
     other than the user that starts Apache has write access to the
     directory where they are written. See the <a
     href="../misc/security_tips.html">security tips</a> document
     for details.</p>
     <!--#include virtual="footer.html" -->
   </body>
 </html>
	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
	"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

	<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
	<meta name="generator" content="HTML Tidy, see www.w3.org" />

	<title>Apache IP-based Virtual Host Support</title>
	</head>
	<!-- Background white, links blue (unvisited), navy (visited), red (active) -->

	<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
	vlink="#000080" alink="#FF0000">
	<!--#include virtual="header.html" -->

	<h1 align="CENTER">Apache IP-based Virtual Host Support</h1>
	<strong>See also:</strong> <a href="name-based.html">Name-based
	Virtual Hosts Support</a>
	<hr />

	<h2>System requirements</h2>
	As the term <cite>IP-based</cite> indicates, the server
	<strong>must have a different IP address for each IP-based
	virtual host</strong>. This can be achieved by the machine
	having several physical network connections, or by use of
	virtual interfaces which are supported by most modern operating
	systems (see system documentation for details, these are
	frequently called "ip aliases", and the "ifconfig" command is
	most commonly used to set them up).

	<h2>How to set up Apache</h2>
	There are two ways of configuring apache to support multiple
	hosts. Either by running a separate httpd daemon for each
	hostname, or by running a single daemon which supports all the
	virtual hosts.

	<p>Use multiple daemons when:</p>

	<ul>
	<li>There are security partitioning issues, such as company1
	does not want anyone at company2 to be able to read their
	data except via the web. In this case you would need two
	daemons, each running with different <a
	href="../mod/mpm_common.html#user">User</a>, <a
	href="../mod/mpm_common.html#group">Group</a>, <a
	href="../mod/mpm_common.html#listen">Listen</a>, and <a
	href="../mod/core.html#serverroot">ServerRoot</a>
	settings.</li>

	<li>You can afford the memory and <a
	href="../misc/descriptors.html">file descriptor
	requirements</a> of listening to every IP alias on the
	machine. It's only possible to <a
	href="../mod/mpm_common.html#listen">Listen</a> to the "wildcard"
	address, or to specific addresses. So if you have a need to
	listen to a specific address for whatever reason, then you
	will need to listen to all specific addresses. (Although one
	httpd could listen to N-1 of the addresses, and another could
	listen to the remaining address.)</li>
	</ul>
	Use a single daemon when:

	<ul>
	<li>Sharing of the httpd configuration between virtual hosts
	is acceptable.</li>

	<li>The machine services a large number of requests, and so
	the performance loss in running separate daemons may be
	significant.</li>
	</ul>

	<h2>Setting up multiple daemons</h2>
	Create a separate httpd installation for each virtual host. For
	each installation, use the <a
	href="../mod/mpm_common.html#listen">Listen</a> directive in the
	configuration file to select which IP address (or virtual host)
	that daemon services. e.g.
	<pre>
	Listen www.smallco.com:80
	</pre>
	It is recommended that you use an IP address instead of a
	hostname (see <a href="../dns-caveats.html">DNS caveats</a>).

	<h2>Setting up a single daemon with virtual hosts</h2>
	For this case, a single httpd will service requests for the
	main server and all the virtual hosts. The <a
	href="../mod/core.html#virtualhost">VirtualHost</a> directive
	in the configuration file is used to set the values of <a
	href="../mod/core.html#serveradmin">ServerAdmin</a>, <a
	href="../mod/core.html#servername">ServerName</a>, <a
	href="../mod/core.html#documentroot">DocumentRoot</a>, <a
	href="../mod/core.html#errorlog">ErrorLog</a> and <a
	href="../mod/mod_log_config.html#transferlog">TransferLog</a>
	or <a href="../mod/mod_log_config.html#customlog">CustomLog</a>
	configuration directives to different values for each virtual
	host. e.g.
	<pre>
	<VirtualHost www.smallco.com>
	ServerAdmin webmaster@mail.smallco.com
	DocumentRoot /groups/smallco/www
	ServerName www.smallco.com
	ErrorLog /groups/smallco/logs/error_log
	TransferLog /groups/smallco/logs/access_log
	</VirtualHost>

	<VirtualHost www.baygroup.org>
	ServerAdmin webmaster@mail.baygroup.org
	DocumentRoot /groups/baygroup/www
	ServerName www.baygroup.org
	ErrorLog /groups/baygroup/logs/error_log
	TransferLog /groups/baygroup/logs/access_log
	</VirtualHost>
	</pre>
	It is recommended that you use an IP address instead of a
	hostname (see <a href="../dns-caveats.html">DNS caveats</a>).

	<p>Almost <strong>any</strong> configuration directive can be
	put in the VirtualHost directive, with the exception of
	directives that control process creation and a few other
	directives. To find out if a directive can be used in the
	VirtualHost directive, check the <a
	href="../mod/directive-dict.html#Context">Context</a> using the
	<a href="../mod/directives.html">directive index</a>.</p>

	<p><a href="../mod/mpm_common.html#user">User</a> and <a
	href="../mod/mpm_common.html#group">Group</a> may be used inside a
	VirtualHost directive if the <a href="../suexec.html">suEXEC
	wrapper</a> is used.</p>

	<p><em>SECURITY:</em> When specifying where to write log files,
	be aware of some security risks which are present if anyone
	other than the user that starts Apache has write access to the
	directory where they are written. See the <a
	href="../misc/security_tips.html">security tips</a> document
	for details.</p>
	<!--#include virtual="footer.html" -->
	</body>
	</html>