Linux Centos7 Firewall related operations

1. Turn off the firewall

systemctl stop firewalld

2. Turn on the firewall

systemctl start firewalld 开启防火墙

3. Check the firewall status

   systemctl status firewalld

4. Open the specified port

firewall-cmd --zone=public --add-port=123/tcp --permanent 
firewall-cmd --reload 重新载入
firewall-cmd --query-port=123/tcp查看端口是否开放成功

5. view all open ports

firewall-cmd --zone=public --list-ports