I have always been fascinated with Docker Swarm and how it can cluster multiple computers together to run containers. I mainly used Swarm via docker-machine with the Virtual Box provider for testing. I felt that now it is time to try and run this in production. This blog post will explain how to create a simple Swarm cluster and secure it with a firewall. Docker officially recommends that you enable TLS on each node but I wanted to make it simpler with firewall rules to prevent unauthorized access.