错误：
[root@VM-0-16-centos ~]# service mysql.server start
Redirecting to /bin/systemctl start mysql.server.service
Failed to start mysql.server.service: Unit not found.
解决办法：
首先需要安装mariadb-server
安装mariadb-server
~]# yum install -y mariadb-server
启动服务
~]# systemctl start mariadb.service
添加到开机启动
~]# systemctl enable mariadb.service
