安装了mysql5.7之后初始密码不再默认为空
1.查看初始密码：
[root@VM_225_102_centos ~]# grep \'temporary password\' /var/log/mysqld.log
2016-07-08T02:25:46.311098Z 1 [Note] A temporary password is generated for root@localhost: MtPqF0/oN5zo
即初始密码为 MtPqF0/oN5zo （密码是随机产生的，每台机器产生的都不一样哦）
2.登录及修改密码：
[root@VM_225_102_centos ~]# mysql -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.11
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> show databases;
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
登录之后 第一步必须先修改密码，否则其他操作都执行不了。
修改密码的方法：
mysql> alter user root@localhost identified by \'tyzZ001!\';
Query OK, 0 rows affected (0.00 sec)
新修改的密码中 必须包含 大小写字母数字及符号