[root@upright91 ~]# mysql -p
Enter password: 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

让人讨厌的故事，解决如下：

1.关库
[root@upright91 ~]#  /etc/init.d/mysql stop
Shutting down MySQL..[  OK  ]

2.修改
[root@upright91 ~]# mysqld_safe --user=mysql --skip-grant-tables --skip-networking &

[root@upright91 ~]# mysql -u root mysql

Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.30 Source distribution

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>
mysql>  UPDATE user SET Password=PASSWORD('mysql123') where USER='root' and host='root' or host='localhost';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> FLUSH PRIVILEGES;

3.起库
[root@upright91 ~]#  /etc/init.d/mysqld restart
Stopping mysqld:  [  OK  ]
Starting mysqld:  [  OK  ]

4.新密码登陆
[root@upright91 ~]#  mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.30 Source distribution


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>