none with containerd: make it possible to run without the `docker` CLI

[inductor]

Steps to reproduce the issue:

This is the current behavior regarding initizliation with none driver with containerd runtime.

# minikube start --driver=none --container-runtime='containerd'
😄  minikube v1.18.1 on Ubuntu 20.04 (amd64)
✨  Using the none driver based on user configuration

🤷  Exiting due to PROVIDER_NONE_NOT_FOUND: The 'none' provider was not found: exec: "docker": executable file not found in $PATH
💡  Suggestion: Install docker
📘  Documentation: https://minikube.sigs.k8s.io/docs/reference/drivers/none/

root@minikube:~# minikube start -h | grep provider
root@minikube:~# minikube start --driver=none --container-runtime='containerd'
😄  minikube v1.18.1 on Ubuntu 20.04 (amd64)
✨  Using the none driver based on user configuration

🤷  Exiting due to PROVIDER_NONE_NOT_FOUND: The 'none' provider was not found: exec: "docker": executable file not found in $PATH
💡  Suggestion: Install docker
📘  Documentation: https://minikube.sigs.k8s.io/docs/reference/drivers/none/

Since Docker is no longer default runtime, I think even none driver should consider the runtime option if specified.

Full output of failed command:

Full output of minikube start command used, if not already included:

Optional: Full output of minikube logs command:

[afbjorklund]

It's a bug, unfortunately: #5549

It should not look for "docker", when wanting to run with containerd.

Since Docker is no longer default runtime

Docker is still the default runtime, though.

[tharun208]

@afbjorklund I like to work on this

[afbjorklund]

I like to work on this

Please do, note that it is not the warning and the early exit that is the real issue here.

        if _, err := exec.LookPath("docker"); err != nil {
                return registry.State{Running: true, Error: err, Installed: false, Fix: "Install docker", Doc: "https://minikube.sigs.k8s.io/docs/reference/drivers/none/"}
        }

So just comment that out while debugging.

We also have some callouts to the Docker daemon, but those should just fail (for now)
So leave those as well, the main issue here is the requirement on the "docker" CLI client.

(the other is #8577)

[tstromberg]

/assign tharun208

[tstromberg]

I haven't looked at the none driver recently, but if it isn't possible to simply remove the docker checks when the none driver is used with non-Docker runtime, https://github.com/containerd/nerdctl may be a helpful alternative.

[inductor]

@tstromberg I'm aware of nerdctl(my friend made it), but I just wanted to setup kubernetes with local runtime without using kubeadm easily. So using nerdctl is not really an option for my use-case

[afbjorklund]

As far as I know, the "docker" issues are because the minikube driver registry is broken

Not because the Docker client is actually required for anything (beyond e.g. docker-env)
And we offer BuildKit as a replacement, if you want to build images for your containerd...

You will have to install crictl though, unfortunately that is not bundled with Kubernetes.