Consider this scenario. You want to create 2 drupal sites
www.crashpoint.com/site1
www.crashpoint.com/site2
Build www.crashpoint.com/site1 as described here [1]
Assume the documentroot of the sites are /var/www/site1 and /var/www/site2 respectively
Setup the first site with drupal being untarred in /var/www/site1
The second site should use the same code base as the first site differing only in the database
There are 2 changes to be made.
Modify the settings.php file for site2 as per the readme of drupal attached to this post. Read the section of CONNECTING DRUPAL which has a detailed description of multiple sites.
Create a symlink from /var/www/site2/site pointing to /var/www/site1/site which has the code base of drupal.
Checkout the multiple sites created at dhandanought.org on public server of starcom for working example.
The directory /var/warehouse/drupal on 10.1.1.6 contains version 4.7.0 of drupal and the customized tarballs of the setups of drupal and NSDL and starcom's public server.