I was installing and setting up Cacti recently and faced following error:
“FATAL: Cannot connect to MySQL server on ‘localhost’.”
This post includes debugging steps and solution for the issue.
Along with the Cacti’s web-interface, the poller.php was generating the same error as follows:
root@ubuntu:/var/www/cacti# php /var/www/cacti/poller.php FATAL: Cannot connect to MySQL server on 'localhost'. Please make sure you have specified a valid MySQL database name in 'include/config.php'