Linux Network Administratoramp;#039;s Guide (3rd Edition) [Electronic resources] نسخه متنی

14.4. VirtualHost Configuration Options

One of the more powerful features of
Apache is the ability to run multiple web servers on one machine.
This functionality is accomplished using the VirtualHost
functionality found within the httpd.conf file.
There are two types of virtual hosts that can be
configurednamed virtual hosts and IP virtual hosts. With named
virtual hosts, you can host multiple TLDs on a single IP, while with
IP virtual hosting, you can host only one virtual host per IP
address. In this section, we will give examples of each, and list
some common configuration options.

14.4.1. IP-Based Virtual Hosts

For those who have only one site to
host or have multiple IPs for all sites they wish to run, IP-based
virtual hosting is the best configuration choice. Consider the
following example where the Virtual Brewery decides to host a web
site for its Virtual Vineyard. The following is the minimum amount of
configuration that would need to be added to the
httpd.conf file in order to create the new web
site.

Listen www.virtualvineyard.com>:80
.
.
<VirtualHost www.virtualvineyard.com>
ServerAdmin webmaster@vbrew.com
DocumentRoot /home/www/virtualvineyard.com
ServerName www.virtualvineyard.com
ErrorLog /var/www/logs/vvineyard.error_log
TransferLog /var/www/logs/vvineyard.access_log
</VirtualHost>

You would also want to make sure that
www.virtualvinyard.com was added to your
/etc/hosts file. This is done because Apache
will need to look up an IP address for this domain when it starts.
You can rely entirely on your DNS, but should your DNS server be
unavailable for some reason when the web server restarts, your web
server will fail. Alternately, you can hardcode the IP address of
your server at the beginning of the configuration in the
<VirtualHost> tag. Doing so may seem more
efficient, however, should you wish to change your web server IP
address, it will require changing your Apache configuration file.

In addition to the configuration
options listed in the example, any of the options discussed earlier
in the chapter can be added to the VirtualHost groups. This provides
you with maximum flexibility for each of your separate web servers.

14.4.2. Name-Based Virtual Hosting

The configuration of
name-based virtual hosting is very similar to the previous example,
with the exception that multiple domains can be hosted on a single IP
address. There are two caveats to this functionality. The
firstperhaps the biggest drawbackis that SSL can be
used only with a single IP address. This is not a problem with
Apache, but rather with SSL and the way certificates work. The second
potential drawback is that some older web browsers, such as those
without the HTTP 1.1 specification, will not work. This is because
name-based virtual hosting relies on the client to inform the server
in the HTTP request header of the site they wish to visit. Nearly any
browser released within the past few years, however, will have HTTP
1.1 implemented, so this isn't a problem for most
administrators.

Proceeding to an example configuration, we will use the same example
given earlier in the chapter, except this time the Virtual Brewery
has only one public IP address. You will first need to inform Apache
that you are using named virtual hosting, and then provide the detail
on your sites as is shown in this example.

NameVirtualHost 172.16.0.199
<VirtualHost 172.16.0.199>
ServerName www.vbrew.com
DocumentRoot /home/www/vbrew.com
</VirtualHost>
<VirtualHost 172.16.0.199>
ServerName www.virtualvineyard.com
DocumentRoot /home/www/vvineyard.com
</VirtualHost>

For the sake of clarity, the additional options were omitted, but any
of the previously discussed options can be added as
necessary.