这是firewalld服务被锁定了，所以取消firewalld的锁定即可。
取消firewalld的锁定
systemctl unmask firewalld开启防火墙
systemctl start firewalld查看防火墙状态
systemctl status firewalld
centos6打开firewall遇到unit firewall.service is masked
原文：https://www.cnblogs.com/Aiahtwo/p/12968690.html