Managing Ports on CentOS

Control the firewalld service daemon:

# Activate the firewall service
systemctl start firewalld.service

# Deactivate the firewall service
systemctl stop firewalld.service

# Check current service status
systemctl status firewalld

Using iptables (CentOS/RHEL 6)

To permit traffic on ports 80 and 443:

iptables -I INPUT -p tcp --dport 80 -j ACCEPT
iptables -I INPUT -p tcp --dport 443 -j ACCEPT
service iptables save

List the current filterign rules:

iptables -L -n

Using firewalld (CentOS/RHEL 7+)

Add permanent rules for specific ports and reload the configuration:

# Open port 80
firewall-cmd --zone=public --permanent --add-port=80/tcp

# Open port 443
firewall-cmd --zone=public --permanent --add-port=443/tcp

# Apply changes
firewall-cmd --reload

Utility commands for firewalld:

# Check if the firewall is active
firewall-cmd --state

# List all currently open ports
firewall-cmd --list-ports

# List available zones
firewall-cmd --get-zones

# Manage services (example with ftp)
firewall-cmd --query-service ftp
firewall-cmd --add-service=ftp --permanent
firewall-cmd --remove-service=ftp --permanent

Managing Ports on Ubuntu and Debian

Using ufw (Uncomplicated Firewall)

Check the current status of the firewall:

sudo ufw status verbose

Alow traffic on ports 80 and 443:

sudo ufw allow 80/tcp
sudo ufw allow 443/tcp
sudo ufw reload

Common ufw operational commands:

# Enable the firewall
sudo ufw enable

# Disable the firewall
sudo ufw disable

# Reset all rules to default
sudo ufw reset

# Deny specific traffic
sudo ufw deny 22/tcp