课堂重点：
实操命令及运行结果：
(centos 6)
service network status
chkconfig --list
chkconfig --level 5 network off
(centos7)
systemctl status firewalld
systemctl stop firewalld
systemctl status firewalld
systemctl list-unit-files
systemctl list-unit-files |grep firewalld
systemctl disable firewalld
systemctl list-unit-files |grep firewalld
文件地址：