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Submitted by: Chris Pepper <pepper@mail.reppep.com> git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86675 13f79535-47bb-0310-9956-ffa450edef68
170 lines
6.6 KiB
HTML
170 lines
6.6 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML><HEAD>
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<TITLE>Apache name-based Virtual Hosts</TITLE>
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</HEAD>
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<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
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<BODY
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#000080"
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ALINK="#FF0000"
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>
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<!--#include virtual="header.html" -->
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<H1 ALIGN="CENTER">Apache name-based Virtual Host Support</H1>
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<STRONG>See Also:</STRONG>
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<A HREF="ip-based.html">IP-based Virtual Host Support</A>
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<HR>
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<H2>Name-based vs. IP-based virtual hosts</H2>
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<P>Early versions of HTTP (like many other protocols, e.g. FTP)
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required a different IP address for each virtual host on the server.
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On some platforms this can limit the number of virtual hosts you can
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run, and because there are concerns about the availability of IP
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addresses it is strongly discouraged by the registraries (ARIN, RIPE,
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and APNIC).</P>
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<P>The <CODE>HTTP/1.1</CODE> protocol, and a common extension to
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<CODE>HTTP/1.0</CODE>, includes a method for the server to identify
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what name it is being addressed as. Apache 1.1 and later support this
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approach as well as the old IP-address-per-hostname method.</P>
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<P>The benefits of using the name-based virtual hosts is a practically
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unlimited number of servers, ease of configuration and use, and it
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requires no additional hardware or software. The main disadvantage is
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that the client must support this part of the protocol. Almost all
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browsers do, but there are still tiny numbers of very old browsers in
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use which do not. This can cause problems, although a possible
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solution is addressed below.</P>
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<H2>Using name-based virtual hosts</H2>
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<P>Using name-based virtual hosts is quite easy, and superficially looks
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like the old method. The notable difference between IP-based and
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name-based virtual host configuration is the
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<A HREF="../mod/core.html#namevirtualhost"><CODE>NameVirtualHost</CODE></A>
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directive which specifies an IP address that should be used as a
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target for name-based virtual hosts, or the wildcard <CODE>*</CODE> to
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indicate that the server only does name-based virtual hosting (no
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IP-based virtual hosting).</P>
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<P>For example, suppose that both <SAMP>www.domain.tld</SAMP> and
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<SAMP>www.otherdomain.tld</SAMP> point at the IP address of your
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server. Then you simply add to one of the Apache configuration files
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(most likely <CODE>httpd.conf</CODE> or <CODE>srm.conf</CODE>) code
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similar to the following:</P>
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<PRE>
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NameVirtualHost *
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<VirtualHost *>
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ServerName www.domain.tld
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DocumentRoot /www/domain
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</VirtualHost>
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<VirtualHost *>
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ServerName www.otherdomain.tld
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DocumentRoot /www/otherdomain
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</VirtualHost>
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</PRE>
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<P>Of course, any additional directives can (and should) be placed
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into the <CODE><VirtualHost></CODE> section. To make this work,
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all that is needed is to make sure that the names
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<SAMP>www.domain.tld</SAMP> and <SAMP>www.otherdomain.tld</SAMP>
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are pointing to the right IP address.
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<P>Note: When you specify an IP address in a <CODE>NameVirtualHost</CODE>
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directive then requests to that IP address will only ever be served
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by matching <VirtualHost>s. The "main server" will
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<STRONG>never</STRONG> be served from the specified IP address.
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If you specify a wildcard then the "main server" isn't used at all.
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If you start to use virtual hosts you should stop using the "main server"
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as an independent server and rather use it as a place for
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configuration directives that are common for all your virtual hosts.
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In other words, you should add a <VirtualHost> section for
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<EM>every</EM> server (hostname) you want to maintain on your server.
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<P>Additionally, many servers may wish to be accessible by more than
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one name. For example, the example server might want to be accessible
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as <CODE>domain.tld</CODE>, or <CODE>www2.domain.tld</CODE>, assuming
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the IP addresses pointed to the same server. In fact, one might want it
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so that all addresses at <CODE>domain.tld</CODE> were picked up by the
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server. This is possible with the
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<A HREF="../mod/core.html#serveralias"><CODE>ServerAlias</CODE></A>
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directive, placed inside the <VirtualHost> section. For
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example:</P>
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<PRE>
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ServerAlias domain.tld *.domain.tld
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</PRE>
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<P>Note that you can use <CODE>*</CODE> and <CODE>?</CODE> as wild-card
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characters.</P>
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<P>You also might need <CODE>ServerAlias</CODE> if you are
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serving local users who do not always include the domain name.
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For example, if local users are
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familiar with typing "www" or "www.foobar" then you will need to add
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<CODE>ServerAlias www www.foobar</CODE>. It isn't possible for the
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server to know what domain the client uses for their name resolution
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because the client doesn't provide that information in the request.
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The <CODE>ServerAlias</CODE> directive is generally a way to have different
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hostnames pointing to the same virtual host.
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</P>
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<H2>Compatibility with Older Browsers</H2>
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<P>As mentioned earlier, there are still some clients in use who
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do not send the required data for the name-based virtual hosts to work
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properly. These clients will always be sent the pages from the
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first virtual host listed for that IP address (the
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<CITE>primary</CITE> name-based virtual host).</P>
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<P>There is a possible workaround with the
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<A HREF="../mod/core.html#serverpath"><CODE>ServerPath</CODE></A>
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directive, albeit a slightly cumbersome one:</P>
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<P>Example configuration:
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<PRE>
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NameVirtualHost 111.22.33.44
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<VirtualHost 111.22.33.44>
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ServerName www.domain.tld
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ServerPath /domain
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DocumentRoot /web/domain
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</VirtualHost>
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</PRE>
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<P>What does this mean? It means that a request for any URI beginning
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with "<SAMP>/domain</SAMP>" will be served from the virtual host
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<SAMP>www.domain.tld</SAMP> This means that the pages can be accessed as
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<CODE>http://www.domain.tld/domain/</CODE> for all clients, although
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clients sending a <SAMP>Host:</SAMP> header can also access it as
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<CODE>http://www.domain.tld/</CODE>.</P>
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<P>In order to make this work, put a link on your primary virtual host's page
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to <SAMP>http://www.domain.tld/domain/</SAMP>
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Then, in the virtual host's pages, be sure to use either purely
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relative links (<EM>e.g.</EM>, "<SAMP>file.html</SAMP>" or
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"<SAMP>../icons/image.gif</SAMP>" or links containing the prefacing
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<SAMP>/domain/</SAMP>
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(<EM>e.g.</EM>, "<SAMP>http://www.domain.tld/domain/misc/file.html</SAMP>" or
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"<SAMP>/domain/misc/file.html</SAMP>").</P>
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<P>This requires a bit of
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discipline, but adherence to these guidelines will, for the most part,
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ensure that your pages will work with all browsers, new and old.</P>
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<P>See also: <A HREF="examples.html#serverpath">ServerPath configuration
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example</A></P>
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<!--#include virtual="footer.html" -->
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</BODY>
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</HTML>
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