Document setting minikube container runtime to docker explicitly

[afbjorklund]

Expected behavior

Since Kubernetes 1.24, the "docker" container runtime is no longer the default

This means that minikube docker-env might no longer work, with the cluster,
unless it has been started with minikube start --container-runtime=docker

So this flag should be explicitly documented, in the Quickstart documentation.

Actual behavior

❌ Exiting due to MK_USAGE: The docker-env command is only compatible with the "docker" runtime, but this cluster was configured to use the "containerd" runtime.

❌ Exiting due to MK_USAGE: The docker-env command is only compatible with the "docker" runtime, but this cluster was configured to use the "crio" runtime.

Information

Docker is still available as a container runtime, but needs to be actively selected.

Kubernetes as a project is moving towards only supporting the CRI standard.
This means that "assuming" a Docker daemon is discouraged, preferring crictl.

Note that CRI is missing some Docker CLI commands, like load and build.

Steps to reproduce the behavior

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Related issues:

• Skaffold should prune images with minikube image rm #5613
• use minikube image load for containerd #5773
• consider using minikube image build #5739
• Consider using minikube image ls #5738

The same goes for other clusters, including installing the new cri-dockerd and crictl.

See https://kubernetes.io/blog/2020/12/02/dockershim-faq/

And https://www.mirantis.com/blog/mirantis-to-take-over-support-of-kubernetes-dockershim-2/

[afbjorklund]

@aaron-prindle @medyagh

Note: Not really changing anything in minikube per se, just making sure that the old skaffold code still works

[tejal29]

Thanks you for the issue. We would appreciate any help from the community on this issue.