Codeigniter error ketika diganti password mysql di linux ubuntu.

kemarin di server ,saya mereset password mysql di linux ubuntu, sehingga aplikasi Codeigniter saya tidak jalan , mengakibatkan error .solusinya gimana pak ya .terlampir error nya pak.

A PHP Error was encountered Severity: Warning

Message: mysqli::real_connect(): (HY000/2002): Connection refused

Filename: mysqli/mysqli_driver.php

Line Number: 201

Backtrace:

File: /var/www/app/application/third_party/MX/Loader.php Line: 109 Function: DB

File: /var/www/app/application/third_party/MX/Loader.php Line: 65 Function: initialize

File: /var/www/app/application/controllers/Init.php Line: 7 Function: __construct

File: /var/www/app/index.php Line: 316 Function: require_once

A Database Error Occurred Unable to connect to your database server using the provided settings.

Filename: controllers/Init.php

Line Number: 7

terimakasih pak jika boleh kasi saran