Docker is two things: there are Docker images, which are like deployable virtual machine images that contain a system bundled up with a minimal environment. It'

Docker is two things: there are Docker images, which are like deployable virtual machine images that contain a system bundled up with a minimal environment. It's a powerful tool that is indispensable in a microservices architecture. Then there's Docker Swarm, which is a system for deploying, distributing, running, and connecting Docker images into a cohesive system. It's conceptually awesome, but in usage it's horrible. The commands are unintuitive, the configuration is difficult and poorly documented, the logging sucks, the networking is confusing, and it does evil unexpected things that punch holes in your firewall without the slightest warning or safety net. It frequently implodes for no obvious reason, is difficult to debug due to the horrible logging, fills up your filesystem because it doesn't clean up after itself, and is a complete nightmare to maintain. I haven't used Kubernetes yet, but by all accounts it's a superior container environment. We're about to switch to it at work. We'll still create Docker images, because that part is great. But we'll deploy those Docker images in Kubernetes. Despite not having used it yet, it can't possibly be worse than Docker swarm.