Kubernetes relies on containerd which works with docker, rkt or anything that works with containerd.

The prefered alternative to docker is rkt.

No they don't. Containerd is the code Moby and Docker are built from, developed at Docker Inc.

Kubernetes will take anything that implements CRI.

https://cri-o.io/

https://kubernetes.io/docs/setup/cri/

All right ! Thanks for the heads up, deeply appreciated.

However, I still stand with rkt rather than docker...

It can be quite complicated if you use a docker version without containerd's CRI. And you do if you follow the version recommendations (because docker has a lot of regressions). GKE does it, so we do it.

Kubelet actually has a translation layer baked into it that it starts in-process when detecting docker, which provides the gRPC CRI interface on a real filesystem socket.

https://github.com/kubernetes/kubernetes/tree/master/pkg/kub...