If you want a Domain Alias to serve pages only from a certain
subdirectory, you can use this mod_rewrite rule in an .htaccess file in
your /htdocs/www directory of your primary hosting account:
Code:
RewriteEngine on
RewriteCond %{HTTP_HOST} alias.com$ [NC]
RewriteCond %{REQUEST_URI} !^/subdir/.*$
RewriteRule ^(.*)$ http://www.original.com/subdir/$1 [R]
Then when requests for the aliased domain come in, the browser will be
redirected to find files in the subdirectory, while still keeping the
domain name of the domain alias in the browser address bar. Files for
the domain alias in the above example would be served from
/htdocs/www/subdir/