Apache Module mod_vhost_alias
Description: | Provides for dynamically configured mass virtual hosting |
---|---|
Status: | Extension |
ModuleIdentifier: | vhost_alias_module |
SourceFile: | mod_vhost_alias.c |
Summary
This module creates dynamically configured virtual hosts, by allowing the IP address and/or the Host:
header of the HTTP request to be used as part of the pathname to determine what files to serve. This allows for easy use of a huge number of virtual hosts with similar configurations.
Note
If mod_alias
or mod_userdir
are used for translating URIs to filenames, they will override the directives of mod_vhost_alias
described below. For example, the following configuration will map /cgi-bin/script.pl
to /usr/local/apache2/cgi-bin/script.pl
in all cases:
ScriptAlias "/cgi-bin/" "/usr/local/apache2/cgi-bin/" VirtualScriptAlias "/never/found/%0/cgi-bin/"
Directory Name Interpolation
All the directives in this module interpolate a string into a pathname. The interpolated string (henceforth called the "name") may be either the server name (see the UseCanonicalName
directive for details on how this is determined) or the IP address of the virtual host on the server in dotted-quad format. The interpolation is controlled by specifiers inspired by printf
which have a number of formats:
%% | insert a %
|
%p | insert the port number of the virtual host |
%N.M | insert (part of) the name |
N
and M
are used to specify substrings of the name. N
selects from the dot-separated components of the name, and M
selects characters within whatever N
has selected. M
is optional and defaults to zero if it isn't present; the dot must be present if and only if M
is present. The interpretation is as follows:
0 | the whole name |
1 | the first part |
2 | the second part |
-1 | the last part |
-2 | the penultimate part |
2+ | the second and all subsequent parts |
-2+ | the penultimate and all preceding parts |
1+ and -1+
| the same as 0
|
If N
or M
is greater than the number of parts available a single underscore is interpolated.
Examples
For simple name-based virtual hosts you might use the following directives in your server configuration file:
UseCanonicalName Off VirtualDocumentRoot "/usr/local/apache/vhosts/%0"
A request for http://www.example.com/directory/file.html
will be satisfied by the file /usr/local/apache/vhosts/www.example.com/directory/file.html
.
For a very large number of virtual hosts it is a good idea to arrange the files to reduce the size of the vhosts
directory. To do this you might use the following in your configuration file:
UseCanonicalName Off VirtualDocumentRoot "/usr/local/apache/vhosts/%3+/%2.1/%2.2/%2.3/%2"
A request for http://www.domain.example.com/directory/file.html
will be satisfied by the file /usr/local/apache/vhosts/example.com/d/o/m/domain/directory/file.html
.
A more even spread of files can be achieved by hashing from the end of the name, for example:
VirtualDocumentRoot "/usr/local/apache/vhosts/%3+/%2.-1/%2.-2/%2.-3/%2"
The example request would come from /usr/local/apache/vhosts/example.com/n/i/a/domain/directory/file.html
.
Alternatively you might use:
VirtualDocumentRoot "/usr/local/apache/vhosts/%3+/%2.1/%2.2/%2.3/%2.4+"
The example request would come from /usr/local/apache/vhosts/example.com/d/o/m/ain/directory/file.html
.
A very common request by users is the ability to point multiple domains to multiple document roots without having to worry about the length or number of parts of the hostname being requested. If the requested hostname is sub.www.domain.example.com
instead of simply www.domain.example.com
, then using %3+ will result in the document root being /usr/local/apache/vhosts/domain.example.com/...
instead of the intended example.com
directory. In such cases, it can be beneficial to use the combination %-2.0.%-1.0
, which will always yield the domain name and the tld, for example example.com
regardless of the number of subdomains appended to the hostname. As such, one can make a configuration that will direct all first, second or third level subdomains to the same directory:
VirtualDocumentRoot "/usr/local/apache/vhosts/%-2.0.%-1.0"
In the example above, both www.example.com
as well as www.sub.example.com
or example.com
will all point to /usr/local/apache/vhosts/example.com
.
For IP-based virtual hosting you might use the following in your configuration file:
UseCanonicalName DNS VirtualDocumentRootIP "/usr/local/apache/vhosts/%1/%2/%3/%4/docs" VirtualScriptAliasIP "/usr/local/apache/vhosts/%1/%2/%3/%4/cgi-bin"
A request for http://www.domain.example.com/directory/file.html
would be satisfied by the file /usr/local/apache/vhosts/10/20/30/40/docs/directory/file.html
if the IP address of www.domain.example.com
were 10.20.30.40. A request for http://www.domain.example.com/cgi-bin/script.pl
would be satisfied by executing the program /usr/local/apache/vhosts/10/20/30/40/cgi-bin/script.pl
.
If you want to include the .
character in a VirtualDocumentRoot
directive, but it clashes with a %
directive, you can work around the problem in the following way:
VirtualDocumentRoot "/usr/local/apache/vhosts/%2.0.%3.0"
A request for http://www.domain.example.com/directory/file.html
will be satisfied by the file /usr/local/apache/vhosts/domain.example/directory/file.html
.
The LogFormat
directives %V
and %A
are useful in conjunction with this module.
VirtualDocumentRoot Directive
Description: | Dynamically configure the location of the document root for a given virtual host |
---|---|
Syntax: | VirtualDocumentRoot interpolated-directory|none |
Default: | VirtualDocumentRoot none |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_vhost_alias |
The VirtualDocumentRoot
directive allows you to determine where Apache HTTP Server will find your documents based on the value of the server name. The result of expanding interpolated-directory is used as the root of the document tree in a similar manner to the DocumentRoot
directive's argument. If interpolated-directory is none
then VirtualDocumentRoot
is turned off. This directive cannot be used in the same context as VirtualDocumentRootIP
.
Note
VirtualDocumentRoot
will override any DocumentRoot
directives you may have put in the same context or child contexts. Putting a VirtualDocumentRoot
in the global server scope will effectively override DocumentRoot
directives in any virtual hosts defined later on, unless you set VirtualDocumentRoot
to None
in each virtual host. VirtualDocumentRootIP Directive
Description: | Dynamically configure the location of the document root for a given virtual host |
---|---|
Syntax: | VirtualDocumentRootIP interpolated-directory|none |
Default: | VirtualDocumentRootIP none |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_vhost_alias |
The VirtualDocumentRootIP
directive is like the VirtualDocumentRoot
directive, except that it uses the IP address of the server end of the connection for directory interpolation instead of the server name.
VirtualScriptAlias Directive
Description: | Dynamically configure the location of the CGI directory for a given virtual host |
---|---|
Syntax: | VirtualScriptAlias interpolated-directory|none |
Default: | VirtualScriptAlias none |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_vhost_alias |
The VirtualScriptAlias
directive allows you to determine where Apache httpd will find CGI scripts in a similar manner to VirtualDocumentRoot
does for other documents. It matches requests for URIs starting /cgi-bin/
, much like ScriptAlias
/cgi-bin/
would.
VirtualScriptAliasIP Directive
Description: | Dynamically configure the location of the CGI directory for a given virtual host |
---|---|
Syntax: | VirtualScriptAliasIP interpolated-directory|none |
Default: | VirtualScriptAliasIP none |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_vhost_alias |
The VirtualScriptAliasIP
directive is like the VirtualScriptAlias
directive, except that it uses the IP address of the server end of the connection for directory interpolation instead of the server name.
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