replace `load docker-image` with `load container-image` to support multiple providers #4053

Blaimi · 2025-11-23T21:01:22Z

This POC abstracts docker save to the providers so that images from podman and nerdctl can also be used with the load container-image command can be used instead of restrict it to docker with load docker-image.

TBD

With this implementation, you can only use the same provider for loading images as is used for running kind. I.e. it is not possible to load an image from podman and have the cluster running in docker. Changing this would either need to have multiple commands (like load {docker,podman,nerdctl}-image and/or have additional configuration options like KIND_EXPERIMENTAL_PROVIDER.

TODO

ajust unit-tests
run actual tests (didn't even test it on my machine)
better abstraction of the backwards-compatibility code for load docker-image because it is actually copy&paste with very small ajustments.

Fix: #2038
Relates: GoogleContainerTools/skaffold#9901

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linux-foundation-easycla · 2025-11-23T21:01:30Z

The committers listed above are authorized under a signed CLA.

✅ login: Blaimi / name: Matthias Blümel (20c7c47, 720bccc, bdb442c, ce0c0db)

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k8s-ci-robot · 2025-11-23T21:01:32Z

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stmcginnis

With this implementation, you can only use the same provider for loading images as is used for running kind. I.e. it is not possible to load an image from podman and have the cluster running in docker.

I think that's fine and would probably be the expected/desired behavior for most users.

pkg/cmd/kind/load/container-image/container-image.go

pkg/cmd/kind/load/docker-image/docker-image.go

pkg/cmd/kind/load/load.go

stmcginnis · 2025-11-24T14:33:48Z

pkg/cmd/kind/load/docker-image/docker-image.go

+		Short:      "Loads docker images from host into nodes",
+		Long:       "Loads docker images from host into all or specified nodes by name",
+		Deprecated: "Please use 'kind load container-image' instead of 'kind load docker-image', 'docker-image' will be removed in future releases and is restricted to the docker-provider.",
 		RunE: func(cmd *cobra.Command, args []string) error {


I haven't looked closely, but can we have this command just call the new code?

No. This would break existing installations, where the image is built/available via docker but the cluster runs on podman/nerdctl. I'm a huge fan of not breaking stuff because of new features ;-)

BenTheElder

couple quick thoughts

I think this overall makes sense, but it's also not quite the UX discussed in the issue (can't override source, only supports locally stored images ...).

BenTheElder · 2025-11-25T01:11:05Z

pkg/cluster/internal/providers/docker/provider.go

 }

+// ContainerSave saves images to dest, as in `docker save`
+func (p *provider) ContainerSave(images []string, dest string) error {


Saving images from storage isn't really a property of implementing nodes, and this is already a pretty complicated object. I think we should probably split this out.

We also lose the ability to import across providers cleanly, which while a bit weird we probably already have users doing.

Saving images from storage isn't really a property of implementing nodes, and this is already a pretty complicated object. I think we should probably split this out.

Any idea for locations? I would suggest pkg/cmd/kind/load/providers/*/provider.go

We also lose the ability to import across providers cleanly, which while a bit weird we probably already have users doing.

Can you explain that? load docker-image will be backwards compatible.

BenTheElder · 2025-11-25T01:12:08Z

pkg/cmd/kind/load/container-image/container-image.go

@@ -0,0 +1,262 @@
+/*
+Copyright 2019 The Kubernetes Authors.


new files should drop the year (previously they should've had the year of creation, so 2025 here)

dropping the year is ... new kubernetes/steering#299

BenTheElder · 2025-11-25T01:14:20Z

pkg/cmd/kind/load/container-image/container-image.go

+		return
+	}
+	exists = true
+	sanitizedImage = sanitizeImage(imageName)


this may be inaccurate on podman where the user may have configured a different default image host because :reasons:

for our own node images, forcing the default host we actually use makes sense, for user's images ... maybe not

Any suggestion? Just not sanitizing will lead to an error then—or make the command interactive which might lead to new problems …

BenTheElder

renaming the existing command, modifying it, and then back-adding a supposedly compatible version seems ... far more confusing than just introducing a new command to begin with and leaving the existing one ~untouched

Blaimi · 2025-11-25T03:41:57Z

renaming the existing command, modifying it, and then back-adding a supposedly compatible version seems ... far more confusing than just introducing a new command to begin with and leaving the existing one ~untouched

That's for the long run of the git history. Once the then deprecated load docker-image is removed, the history of the files has the correct origins. And I'm not happy with this implementation because it contains a lot of duplicate code. If this gets resolved with clean abstractions, it might make even more sense to "rename&add for bc" instead of "add new&deprecate"

k8s-ci-robot added do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. area/provider/docker Issues or PRs related to docker labels Nov 23, 2025

k8s-ci-robot requested review from aojea and stmcginnis November 23, 2025 21:01

k8s-ci-robot added area/provider/nerdctl Issues or PRs related to nerdctl area/provider/podman Issues or PRs related to podman labels Nov 23, 2025

k8s-ci-robot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Nov 23, 2025

Blaimi force-pushed the feature/2038_load-with-providers branch from 650366c to 7f09e46 Compare November 23, 2025 23:45

Blaimi changed the title ~~Feature/2038 load with providers~~ replace load docker-image with load container-image to support multiple providers Nov 23, 2025

stmcginnis reviewed Nov 24, 2025

View reviewed changes

Blaimi added 4 commits November 24, 2025 16:32

rename docker-image to container-image

20c7c47

give load image-container an alias for load image

bdb442c

move save and imageID to providers

ce0c0db

add docker-image command for backwards compatibility

720bccc

Blaimi force-pushed the feature/2038_load-with-providers branch from 7f09e46 to 720bccc Compare November 24, 2025 15:33

BenTheElder reviewed Nov 25, 2025

View reviewed changes

replace load docker-image with load container-image to support multiple providers #4053

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replace `load docker-image` with `load container-image` to support multiple providers #4053

replace `load docker-image` with `load container-image` to support multiple providers #4053

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