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

啟動mysql：
systemctl start mysqld
systemctl enable mysqld

查看mysql的隨機密碼：
grep ‘temporary password‘ /var/log/mysqld.log

進入mysql更改密碼：
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‘;

CentOS7.5安裝MySQL5.7