无法使用Mysql根帐户登录，但是在Ubuntu 16.04中使用sudo命令时可以登录

Question

Can't login with Mysql root account but can login when use sudo command in ubuntu 16.04

bluebird:~$ mysql -u root -p
Enter password: 
ERROR 1698 (28000): Access denied for user 'root'@'localhost'
bluebird:~$ mysql -u root -p
Enter password: 
ERROR 1698 (28000): Access denied for user 'root'@'localhost'
bluebird:~$ sudo mysql -uroot
[sudo] password for bluebird: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 21
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> 

When I use mysql -u root -p , I can't login. When I use sudo mysql -u root , i can.

And I don't have the password for the root user of MySQL.

I don't know why.

Answer 1

I used the command below:

use mysql;
select User, Host from user;

It turns out, somehow I got 'root'@'XXXXX-aspire','root'@'localhost' and 'root'@'%'.

When I delete 'root'@'XXXXX-aspire', I can login by mysql -uroot without problem.

Answer 2

Try this as SUDO then try login without sudo

GRANT ALL PRIVILEGES ON *.*  TO 'root'@'localhost';
FLUSH PRIVILEGES;