MySQL Access denied for user 'root'@'localhost'

ubuntu-mysql-fix

```bash
# open the mysql terminal
sudo mysql -u root
```

```text
use mysql;
SELECT User, Host, plugin, authentication_string FROM user;
UPDATE user SET plugin='mysql_native_password', authentication_string=PASSWORD('123456') WHERE User='root';
FLUSH PRIVILEGES;
exit;
```

```bash
# restart mysql
sudo service mysql restart
```