ufw (firewall)

1. sudo ufw enable
2. sudo ufw status or sudo ufw status versbose
3. SSH
   1. 1sudo ufw allow ssh or sudo ufw allow 22/tcp or sudo ufw allow 22/tcp comment 'Open port ssh tcp'

References

• https://www.cyberciti.biz/faq/ufw-allow-incoming-ssh-connections-from-a-specific-ip-address-subnet-on-ubuntu-debian/