Common operations of Linux (centos) firewall

        1. View the current status of the firewall

systemctl status firewalld

        2. Turn on the firewall

systemctl start firewalld

        3. Turn off the firewall

systemctl stop firewalld.service

        4. If an error is reported: -bash: firewall- cmd : command not found , the firewall may not be installed . Install command:

yum install firewalld

        5. Open the port, remember to restart the firewall after executing the command

# permanent 永久生效,没有此参数重启后失效

firewall-cmd --zone=public --add-port=8080/tcp --permanent
 
firewall-cmd --zone=public --add-port=1000-2000/tcp --permanent

        6. Remember to restart after the change to make the settings take effect 

# 重启防火墙
firewall-cmd --reload

        7. View all open ports on the firewall, both are ok

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

firewall-cmd --list-ports

        8. Check whether the specified port is open

firewall-cmd --zone=public --query-port=80/tcp

        9. Delete port

firewall-cmd --zone=public --remove-port=80/tcp --permanent

        10. Disable the firewall from booting

firewall systemctl disable firewalld.service

        11. Commonly used ports that need to be opened

# SSH：22
firewall-cmd --zone=public --add-port=22/tcp --permanent

# IIS（HTTP）：80
firewall-cmd --zone=public --add-port=80/tcp --permanent

# MySQL：3306
firewall-cmd --zone=public --add-port=3306/tcp --permanent

# redis：6379
firewall-cmd --zone=public --add-port=6379/tcp --permanent

# django：8000 
firewall-cmd --zone=public --add-port=8000/tcp --permanent

# SQLServer：1433
firewall-cmd --zone=public --add-port=1433/tcp --permanent

# Oracle：1521
firewall-cmd --zone=public --add-port=1521/tcp --permanent

# FTP：21
firewall-cmd --zone=public --add-port=21/tcp --permanent

# Tomcat：8080
firewall-cmd --zone=public --add-port=8080/tcp --permanent

# Telnet ：23
firewall-cmd --zone=public --add-port=23/tcp --permanent