Ubuntu mysqldoes not listen on TCP / IP connections by default . It just uses a local socket.
The current local socket is configured in /etc/mysql/my.cnf. If you open this file, you should find something similar to:
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
PHPMyAdmin (config.inc.php) . , PHPMyAdmin , , , . (, , my.cnf):
$cfg['Servers'][$i]['socket'] = '/var/run/mysqld/mysqld.sock';