Kind: First class image side-loading support

[BenTheElder]

This will be very useful for CI tasks. Currently this is achievable by adding image archives to a node image in /kind/images/ but we should support this first-class.

cc @munnerz @sebastienvas

/kind feature
/priority important-longterm

/assign

[neolit123]

the pause image has a bit of a special case in terms of the kubelet:
https://github.com/kubernetes/kubeadm/issues/1186#issuecomment-433383514

[BenTheElder]

/lifecycle active
FYI @liztio

[BenTheElder]

Rough design I didn't finish implementing:

kind load docker-image [--name=clustername] [--nodes=] image...
kind load image-archive [--name=clustername] [--nodes=] /path/to/image.tar

• implicitly load to all nodes if --nodes is unset
• load to specific nodes if --nodes is a comma separated list of node of names

kind load docker-image should pipe docker save image/name on the host to loading on each of the nodes, IE essentially be kind load image-archive <(docker save image).

[rohansingh]

@BenTheElder That seems very reasonable to me. I'm happy to do a first-pass on the implementation if nobody else is; being able to load images is a blocker for my use case.

[stevesloka]

I should have posted here @rohansingh but I just about have a PR ready to solve this.

[BenTheElder]

309

https://kind.sigs.k8s.io/docs/user/quick-start/#loading-an-image-into-your-cluster

[rohansingh]

Thanks again @BenTheElder and @stevesloka. This is invaluable for the "local clusters on developer machines" use case.

[BenTheElder]

I hope it will make CI better as well!

kind uses a similar technique internally to load Kubernetes and avoid needing to push images when testing from Kubernetes source, so far that has been great 😄