Multiple Drupal sites one CiviCRM installation

From Ethan Winn:

I finally got around to installing 4.6.1 to see if the "double vision" problem persisted (so far I haven't it on 4.6, but it persists on drupal from cvs). In the process of testing this I wanted to switch between two drupal front ends and the same CiviCRM install. I have CCRM installed in /var/www/civicrm and symlinked into my drupal modules directories, but I had to tweak the config.inc.php page in civicrm/modules to allow the same civicrm install to be used on both 4.6 and cvs. Here's what the first few lines of my config.inc.php file ended up looking like:

// BEGIN CODE SNIP

global $user_home,$base_url;

$user_home = '/var/www/civicrm';

define( 'CRM_SMARTYDIR' , $user_home . DIRECTORY_SEPARATOR . 'packages' .
DIRECTORY_SEPARATOR . 'Smarty' . DIRECTORY_SEPARATOR );

define( 'CRM_HTTPBASE' , $base_url . DIRECTORY_SEPARATOR );
define( 'CRM_RESOURCEBASE', $base_url . DIRECTORY_SEPARATOR .
'modules' . DIRECTORY_SEPARATOR . 'civicrm' . DIRECTORY_SEPARATOR );
define( 'CRM_MAINMENU' , $base_url . DIRECTORY_SEPARATOR . 'civicrm' . DIRECTORY_SEPARATOR );

// END CODE SNIP

Note that you need to add base_url to the global declaration at the top of the file.

While this does assume a fairly standard drupal configuration, one nice feature is that it would allow multiple drupal sites to use on CiviCRM installation.

Just thought I'd share in case someone was trying to do something similar.