MySQL5.6 安装后，root会生成一个随机密码，无法用root登陆，可用以下方法重置root密码：
1、 /etc/init.d/mysql start --skip-grant-tables ----启动MySQL服务
2、登入数据库用updatetable的方式修改root密码
[root@ha02 mysql]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.24 MySQL Community Server (GPL)
Copyright (c) 2000, 2015, 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> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> update user set password=PASSWORD('root') where user="root";
Query OK, 4 rows affected (0.00 sec)
Rows matched: 4 Changed: 4 Warnings: 0
mysql> exit
3、重启MySQL服务，用重置后的密码即可登陆
[root@ha02 mysql]# service mysql restart
Shutting down MySQL.. SUCCESS!
Starting MySQL. SUCCESS!
[root@ha02 mysql]# mysql -uroot -proot
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.24
Copyright (c) 2000, 2015, 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>
4、登陆后还需要设置root密码
mysql> show variables like '%buffer%'
-> ;
ERROR 1820 (HY000): You must SET PASSWORD before executing this statement
mysql> set password=PASSWORD('root');
Query OK, 0 rows affected (0.07 sec)
mysql> show variables like '%buffer%';
+-------------------------------------+----------------+
| Variable_name | Value |
+-------------------------------------+----------------+
| bulk_insert_buffer_size | 8388608 |
| innodb_buffer_pool_dump_at_shutdown | OFF |
| innodb_buffer_pool_dump_now | OFF |
| innodb_buffer_pool_filename | ib_buffer_pool |