升级版mysql

    1. rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm 
    2. rpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpm
    3. sudo yum install mariadb-server mariadb
    4. sudo systemctl start mariadb
    5. mysqladmin -u root -p password # 修改密码