Database connection failed!

Stack Trace:

File: /var/www/html/au_user/htdocs/lib/pkp/includes/bootstrap.inc.php line 41
Function: PKPApplication->__construct()

File: /var/www/html/au_user/htdocs/index.php line 65
Function: require("/var/www/html/au_user/htdocs/lib/pkp/includes/bootstrap.inc.php")