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Apache HTTP Server Version 1.3
Apache IP-based Virtual Host Support
See also:
Name-based
Virtual Hosts Support
System requirements
As the term IP-based indicates, the server must have a different IP
address for each IP-based virtual host. 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).
How to set up Apache
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.
Use multiple daemons when:
- 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
User,
Group,
Listen, and
ServerRoot settings.
- You can afford the memory and
file descriptor requirements
of listening to every IP alias on the machine. It's only possible to
Listen 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.)
Use a single daemon when:
- Sharing of the httpd configuration between virtual hosts is acceptable.
- The machine services a large number of requests, and so the performance loss in running
separate daemons may be significant.
Setting up multiple daemons
Create a separate httpd installation for each virtual host. For each installation, use the
Listen directive in the
configuration file to select which IP address (or virtual host) that daemon services. e.g.
Listen www.smallco.com:80
It is recommended that you use an IP address instead of a hostname (see
DNS caveats).
Setting up a single daemon with virtual hosts
For this case, a single httpd will service requests for the main server and all the virtual
hosts. The
VirtualHost
directive in the configuration file is used to set the values of
ServerAdmin,
ServerName,
DocumentRoot,
ErrorLog and
TransferLog or
CustomLog
configuration directives to different values for each virtual host. e.g.
<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>
It is recommended that you use an IP address instead of a hostname (see
DNS caveats).
Almost any 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
Context using the
directive index.
User and
Group may be used inside a
VirtualHost directive if the
suEXEC wrapper
is used.
SECURITY: 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
security tips document for
details.
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