安装mysql源：
yum -y localinstall http://dev.mysql.com/get/mysql57-community-release-el7-7.noarch.rpm

安装mysql-5.7：
yum -y install mysql-community-server mysql-community-devel

启动mysql：
systemctl start mysqld
systemctl enable mysqld

查看mysql的随机密码：
grep 'temporary password' /var/log/mysqld.log

进入mysql更改密码：
mysql -uroot -p'eZa?x2q;&;l%'

set global validate_password_policy=0;
set global validate_password_length=1;
ALTER USER 'root'@'localhost' IDENTIFIED BY 'redhat';