UFW cheatsheet

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