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Friday, April 30, 2010

Apache virtual host configuration examples


This document attempts to answer the commonly-asked questions about setting up virtual hosts. These scenarios are those involving multiple web sites running on a single server, via name-based or IP-based virtual hosts.


Running several name-based web sites on a single IP address.

Your server has a single IP address, and multiple aliases (CNAMES) point to this machine in DNS. You want to run a web server for www.example.com and www.example.org on this machine.

Note

Creating virtual host configurations on your Apache server does not magically cause DNS entries to be created for those host names. You must have the names in DNS, resolving to your IP address, or nobody else will be able to see your web site. You can put entries in your hosts file for local testing, but that will work only from the machine with those hosts entries.

Server configuration

# Ensure that Apache listens on port 80
Listen 80

# Listen for virtual host requests on all IP addresses
NameVirtualHost *:80


DocumentRoot /www/example1
ServerName www.example.com

# Other directives here


DocumentRoot /www/example2
ServerName www.example.org

# Other directives here
The asterisks match all addresses, so the main server serves no requests. Due to the fact that www.example.comis first in the configuration file, it has the highest priority and can be seen as the default or primary server. That means that if a request is received that does not match one of the specified ServerName directives, it will be served by this first VirtualHost.

Note

You can, if you wish, replace * with the actual IP address of the system. In that case, the argument toVirtualHost must match the argument to NameVirtualHost:
NameVirtualHost 172.20.30.40


# etc ...
However, it is additionally useful to use * on systems where the IP address is not predictable - for example if you have a dynamic IP address with your ISP, and you are using some variety of dynamic DNS solution. Since * matches any IP address, this configuration would work without changes whenever your IP address changes.
The above configuration is what you will want to use in almost all name-based virtual hosting situations. The only thing that this configuration will not work for, in fact, is when you are serving different content based on differing IP addresses or ports.
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Name-based hosts on more than one IP address.

Note

Any of the techniques discussed here can be extended to any number of IP addresses.
The server has two IP addresses. On one (172.20.30.40), we will serve the "main" server, server.domain.comand on the other (172.20.30.50), we will serve two or more virtual hosts.

Server configuration

Listen 80

# This is the "main" server running on 172.20.30.40
ServerName server.domain.com
DocumentRoot /www/mainserver

# This is the other address
NameVirtualHost 172.20.30.50


DocumentRoot /www/example1
ServerName www.example.com

# Other directives here ...


DocumentRoot /www/example2
ServerName www.example.org

# Other directives here ...
Any request to an address other than 172.20.30.50 will be served from the main server. A request to172.20.30.50 with an unknown hostname, or no Host: header, will be served from www.example.com.
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Serving the same content on different IP addresses (such as an internal and external address).

The server machine has two IP addresses (192.168.1.1 and 172.20.30.40). The machine is sitting between an internal (intranet) network and an external (internet) network. Outside of the network, the nameserver.example.com resolves to the external address (172.20.30.40), but inside the network, that same name resolves to the internal address (192.168.1.1).
The server can be made to respond to internal and external requests with the same content, with just oneVirtualHost section.

Server configuration

NameVirtualHost 192.168.1.1
NameVirtualHost 172.20.30.40


DocumentRoot /www/server1
ServerName server.example.com
ServerAlias server
Now requests from both networks will be served from the same VirtualHost.

Note:

On the internal network, one can just use the name server rather than the fully qualified host nameserver.example.com.
Note also that, in the above example, you can replace the list of IP addresses with *, which will cause the server to respond the same on all addresses.
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Running different sites on different ports.

You have multiple domains going to the same IP and also want to serve multiple ports. By defining the ports in the "NameVirtualHost" tag, you can allow this to work. If you try using without the NameVirtualHost name:port or you try to use the Listen directive, your configuration will not work.

Server configuration

Listen 80
Listen 8080

NameVirtualHost 172.20.30.40:80
NameVirtualHost 172.20.30.40:8080


ServerName www.example.com
DocumentRoot /www/domain-80


ServerName www.example.com
DocumentRoot /www/domain-8080


ServerName www.example.org
DocumentRoot /www/otherdomain-80


ServerName www.example.org
DocumentRoot /www/otherdomain-8080
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IP-based virtual hosting

The server has two IP addresses (172.20.30.40 and 172.20.30.50) which resolve to the nameswww.example.com and www.example.org respectively.

Server configuration

Listen 80


DocumentRoot /www/example1
ServerName www.example.com


DocumentRoot /www/example2
ServerName www.example.org
Requests for any address not specified in one of the  directives (such as localhost, for example) will go to the main server, if there is one.
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Mixed port-based and ip-based virtual hosts

The server machine has two IP addresses (172.20.30.40 and 172.20.30.50) which resolve to the nameswww.example.com and www.example.org respectively. In each case, we want to run hosts on ports 80 and 8080.

Server configuration

Listen 172.20.30.40:80
Listen 172.20.30.40:8080
Listen 172.20.30.50:80
Listen 172.20.30.50:8080


DocumentRoot /www/example1-80
ServerName www.example.com


DocumentRoot /www/example1-8080
ServerName www.example.com


DocumentRoot /www/example2-80
ServerName www.example.org


DocumentRoot /www/example2-8080
ServerName www.example.org
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Mixed name-based and IP-based vhosts

On some of my addresses, I want to do name-based virtual hosts, and on others, IP-based hosts.

Server configuration

Listen 80

NameVirtualHost 172.20.30.40


DocumentRoot /www/example1
ServerName www.example.com


DocumentRoot /www/example2
ServerName www.example.org


DocumentRoot /www/example3
ServerName www.example3.net

# IP-based

DocumentRoot /www/example4
ServerName www.example4.edu


DocumentRoot /www/example5
ServerName www.example5.gov
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Using Virtual_host and mod_proxy together

The following example allows a front-end machine to proxy a virtual host through to a server running on another machine. In the example, a virtual host of the same name is configured on a machine at 192.168.111.2. TheProxyPreserveHost On directive is used so that the desired hostname is passed through, in case we are proxying multiple hostnames to a single machine.

ProxyPreserveHost On
ProxyPass / http://192.168.111.2/
ProxyPassReverse / http://192.168.111.2/
ServerName hostname.example.com
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Using _default_ vhosts

_default_ vhosts for all ports

Catching every request to any unspecified IP address and port, i.e., an address/port combination that is not used for any other virtual host.

Server configuration


DocumentRoot /www/default
Using such a default vhost with a wildcard port effectively prevents any request going to the main server.
A default vhost never serves a request that was sent to an address/port that is used for name-based vhosts. If the request contained an unknown or no Host: header it is always served from the primary name-based vhost (the vhost for that address/port appearing first in the configuration file).
You can use AliasMatch or RewriteRule to rewrite any request to a single information page (or script).

_default_ vhosts for different ports

Same as setup 1, but the server listens on several ports and we want to use a second _default_ vhost for port 80.

Server configuration


DocumentRoot /www/default80
# ...


DocumentRoot /www/default
# ...
The default vhost for port 80 (which must appear before any default vhost with a wildcard port) catches all requests that were sent to an unspecified IP address. The main server is never used to serve a request.

_default_ vhosts for one port

We want to have a default vhost for port 80, but no other default vhosts.

Server configuration


DocumentRoot /www/default
...
A request to an unspecified address on port 80 is served from the default vhost. Any other request to an unspecified address and port is served from the main server.
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Migrating a name-based vhost to an IP-based vhost

The name-based vhost with the hostname www.example.org (from our name-based example, setup 2) should get its own IP address. To avoid problems with name servers or proxies who cached the old IP address for the name-based vhost we want to provide both variants during a migration phase.
The solution is easy, because we can simply add the new IP address (172.20.30.50) to the VirtualHostdirective.

Server configuration

Listen 80
ServerName www.example.com
DocumentRoot /www/example1

NameVirtualHost 172.20.30.40


DocumentRoot /www/example2
ServerName www.example.org
# ...


DocumentRoot /www/example3
ServerName www.example.net
ServerAlias *.example.net
# ...
The vhost can now be accessed through the new address (as an IP-based vhost) and through the old address (as a name-based vhost).
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Using the ServerPath directive

We have a server with two name-based vhosts. In order to match the correct virtual host a client must send the correct Host: header. Old HTTP/1.0 clients do not send such a header and Apache has no clue what vhost the client tried to reach (and serves the request from the primary vhost). To provide as much backward compatibility as possible we create a primary vhost which returns a single page containing links with an URL prefix to the name-based virtual hosts.

Server configuration

NameVirtualHost 172.20.30.40


# primary vhost
DocumentRoot /www/subdomain
RewriteEngine On
RewriteRule ^/.* /www/subdomain/index.html
# ...


DocumentRoot /www/subdomain/sub1
ServerName www.sub1.domain.tld
ServerPath /sub1/
RewriteEngine On
RewriteRule ^(/sub1/.*) /www/subdomain$1
# ...


DocumentRoot /www/subdomain/sub2
ServerName www.sub2.domain.tld
ServerPath /sub2/
RewriteEngine On
RewriteRule ^(/sub2/.*) /www/subdomain$1
# ...
Due to the ServerPath directive a request to the URL http://www.sub1.domain.tld/sub1/ is always served from the sub1-vhost.
A request to the URL http://www.sub1.domain.tld/ is only served from the sub1-vhost if the client sent a correct Host: header. If no Host: header is sent the client gets the information page from the primary host.
Please note that there is one oddity: A request to http://www.sub2.domain.tld/sub1/ is also served from the sub1-vhost if the client sent no Host: header.
The RewriteRule directives are used to make sure that a client which sent a correct Host: header can use both URL variants, i.e., with or without URL prefix.

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