So, Kubernetes is deprecating Docker support and you're either nervous or confused. That's okay! I would like to help you understand what's happening. A thread! 1/10

From Kubernetes v1.20, you will receive a deprecation warning for Docker. After that, you will need to use a different container runtime. Yes, this will break your clusters. You might think that Docker == Kubernetes. Not so! 2/10

The thing we call Docker is actually an entire tech stack, which includes a thing called containerd as well as some other stuff, like some fancy UX changes that make it easier for humans to interact with. Containerd is a high-level container runtime by itself. 3/10

Kubernetes doesn't need all of that fancy UX stuff, though. It just needs the container runtime. Using Docker, the whole stack, as your container runtime means Kubernetes has to use something called dockershim to interact with the parts it actually needs. 4/10

This is because Docker isn't CRI (Container Runtime Interface) compliant. Dockershim allows us to get around that, but it also means we have an entirely separate thing to maintain just so we can use Docker as our runtime. 5/10

This kind of sucks. It's inconvenient. The solution is to cut out the abstraction and just use containerd as our container runtime in Kubernetes. Because, again, Kubernetes isn't a human -- it doesn't need the UX enhancements. 6/10

So, you don't need to panic. Docker isn't dead (yet), and it still has its uses. You just can't use it as your container runtime in Kubernetes anymore. After the next version, you need to switch to containerd. 7/10

Yes, you COULD just stay on an old version of Kubernetes. No, you absolutely should not, or else @IanColdwater will haunt your clusters. 8/10

The Kubernetes docs for container runtimes are here, with info about using containerd or CRI-O:
https://kubernetes.io/docs/setup/production-environment/container-runtimes/ 9/10

Anyway, I hope this helped allay some anxiety or misunderstandings. If you're still confused, that's okay! Ask questions! This is REALLY complicated. Your questions aren't stupid, even if they're simple! 10/10

BONUS TWEET: Yes, Kubernetes will still run images built by Docker! TL;DR not a whole lot will change for devs, those images are still compliant with OCI (Open Container Initiative) and containerd knows what to do with them.

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