This either means that the username and password information in your
settings.php file is incorrect or we can't contact the MySQL database server. This could mean your hosting provider's database server is down.
The MySQL error was: Can't connect to MySQL server on 'mysql' (111).
Currently, the username is admin and the database server is mysql.
For more help, see the Installation and upgrading handbook. If you are unsure what these terms mean you should probably contact your hosting provider.