This is a note for MySQL 5.7 Users
----------------------------------

In 5.7 (e.g. on Ubuntu 16.04) there is a new authentication schema
https://dev.mysql.com/doc/mysql-security-excerpt/5.7/en/socket-authentication-plugin.html
and authentication as in the previous database versions, will not work.

As a quick solution, you can restore the old authentication as follows:

root@ubuntu16:/home/ntop# mysql -uroot -hlocalhost
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.13-0ubuntu0.16.04.2 (Ubuntu)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> ^DBye

root@ubuntu16:/home/ntop# mysql -uroot -h127.0.0.1
ERROR 1698 (28000): Access denied for user 'root'@'localhost'

root@ubuntu16:/home/ntop# mysql -uroot -hlocalhost
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.13-0ubuntu0.16.04.2 (Ubuntu)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> update mysql.user set plugin="mysql_native_password";
Query OK, 1 row affected (0,00 sec)
Rows matched: 3  Changed: 1  Warnings: 0
mysql> flush privileges;
Query OK, 0 rows affected (0,01 sec)
mysql> ^DBye


root@ubuntu16:/home/ntop# mysql -uroot -h127.0.0.1
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 5.7.13-0ubuntu0.16.04.2 (Ubuntu)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.