Allow connections
sudo ufw allow 80/tcp
sudo ufw allow 80
sudo ufw allow http sudo ufw allow https sudo ufw allow ssh
Deny connections
sudo ufw deny 3306
Enable UFW
sudo ufw enable
Check UFW status
sudo ufw status
Disable/reload/restart UFW
sudo ufw disable sudo ufw enable sudo ufw reload
Removing rules
sudo ufw status numbered sudo ufw delete [number]
Enabling IPv6 support
sudo nano /etc/default/ufw
IPV6=yes
Show app list
sudo ufw app list
Show app info
sudo ufw app info OpenSSH
Back to default settings
sudo ufw reset
Start automatically on boot
sudo systemctl enable ufw
References
https://www.vultr.com/docs/how-to-configure-ufw-firewall-on-ubuntu-14-04
https://www.digitalocean.com/community/tutorials/ufw-essentials-common-firewall-rules-and-commands
https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-with-ufw-on-ubuntu-18-04