#查看防火牆狀態
systemctl status firewalld

#開啟防火牆
systemctl start firewalld

#關閉防火牆
systemctl stop firewalld

#查看當前firewall狀態
firewall-cmd –state

#重啟firewall 
firewall-cmd –reload

#查看已經開放的端口：
firewall-cmd –list-ports

#開啟端口
firewall-cmd –zone=public –add-port=80/tcp –permanent 
#開啟端口後需要重啟防火牆

命令含義：
–zone #作用域
–add-port=80/tcp #添加端口，格式為：端口/通訊協議
–permanent #永久生效，沒有此參數重啟後失效

#多個端口: 
firewall-cmd –zone=public –add-port=80-90/tcp –permanent

#刪除端口
firewall-cmd –zone=public –remove-port=80/tcp –permanent

#設置開機啟用防火牆
systemctl enable firewalld.service 
#設置開機不啟動防火牆
systemctl disable firewalld.service

#查看本機已經啟用的監聽端口: 
#centos7以下使用netstat -ant,7使用ss 
ss -ant

#centos7查看防火牆所有信息
firewall-cmd –list-all

#centos7查看防火牆開放的端口信息
firewall-cmd –list-ports