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This module provides support for dynamically configured mass virtual hosting.
Status: Extension
     Source File:
    mod_vhost_alias.c
     Module Identifier:
    vhost_alias_module
     Compatibility: Available in
    Apache 1.3.7 and later.
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.
See also: UseCanonicalName.
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:
%%%%p%N.MN 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:
012-1-22+-2+1+ and -1+0If N or M is greater than the
    number of parts available a single underscore is
    interpolated.
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.example.isp.com/directory/file.html
    will be satisfied by the file
    /usr/local/apache/vhosts/isp.com/e/x/a/example/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/isp.com/e/l/p/example/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/isp.com/e/x/a/mple/directory/file.html.
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.example.isp.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.example.com were
    10.20.30.40. A request for
    http://www.example.isp.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.example.isp.com/directory/file.html
    will be satisfied by the file
    /usr/local/apache/vhosts/example.isp/directory/file.html.
The LogFormat
    directives %V and %A are useful
    in conjunction with this module.
Syntax: VirtualDocumentRoot
    interpolated-directory
     Default: None
     Context: server config, virtual
    host
     Status: Extension
     Module: mod_vhost_alias
     Compatibility:
    VirtualDocumentRoot is only available in 1.3.7 and later.
The VirtualDocumentRoot directive allows you to
    determine where Apache 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.
Syntax: VirtualDocumentRootIP
    interpolated-directory
     Default: None
     Context: server config, virtual
    host
     Status: Extension
     Module: mod_vhost_alias
     Compatibility:
    VirtualDocumentRootIP is only available in 1.3.7 and later.
The VirtualDocumentRootIP directive is like the
    VirtualDocumentRoot
    directive, except that it uses the IP address of the server end
    of the connection instead of the server name.
Syntax: VirtualScriptAlias
    interpolated-directory
     Default: None
     Context: server config, virtual
    host
     Status: Extension
     Module: mod_vhost_alias
     Compatibility:
    VirtualScriptAlias is only available in 1.3.7 and later.
The VirtualScriptAlias directive allows you to
    determine where Apache 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.
Syntax: VirtualScriptAliasIP
    interpolated-directory
     Default: None
     Context: server config, virtual
    host
     Status: Extension
     Module: mod_vhost_alias
     Compatibility:
    VirtualScriptAliasIP is only available in 1.3.7 and later.
The VirtualScriptAliasIP directive is like the
    VirtualScriptAlias
    directive, except that it uses the IP address of the server end
    of the connection instead of the server name.
 
    