(chore) Remove docker installation ++

[awesomenix]

What type of PR is this?

/kind cleanup
/kind deprecation

What this PR does / why we need it:

Docker and dockershim were removed from Kubernetes in version 1.24. This change removes all Docker-related installation, configuration, and runtime code from AgentBaker, as containerd is now the only supported container runtime.

aks-node-controller/helpers/utils.go

• Removed conditional logic for dockerShim flag removal
• Now unconditionally removes dockerShim flags since Docker is no longer supported
• Flags removed: --cni-bin-dir, --cni-cache-dir, --cni-conf-dir, --docker-endpoint, --image-pull-progress-deadline, --network-plugin, --network-plugin-mtu

pkg/agent/baker.go

• Applied same unconditional dockerShim flag removal in ValidateAndSetLinuxNodeBootstrappingConfiguration()
• Removed unused profile variable after eliminating containerd runtime check
• Removed template functions: IsDockerContainerRuntime and RequiresDocker
• Added comments explaining Docker removal in Kubernetes 1.24

parts/linux/cloud-init/artifacts/cse_config.sh

• Removed ensureDocker() function (lines 414-432)
• Function was responsible for starting Docker service and configuring daemon.json

parts/linux/cloud-init/artifacts/cse_main.sh

• Removed conditional Docker/containerd runtime selection
• Now always calls ensureContainerd since it's the only supported runtime
• Removed Docker login logic for private registry authentication
• Private registry auth is now handled through containerd configuration

parts/linux/cloud-init/artifacts/cse_cmd.sh

• Removed NEEDS_DOCKER_LOGIN template variable
• Variable was used to determine if Docker login was needed for private registries

parts/linux/cloud-init/artifacts/cse_install.sh

• Removed call to installMoby() in installContainerRuntime()
• Added shellcheck directive for cleanupImagesRun() function (unrelated fix)

pkg/agent/datamodel/types.go

• NeedsContainerd() method already updated to always return true
• RequiresDocker() method already deprecated and always returns false
• Both methods kept for backwards compatibility with clear deprecation comments

pkg/agent/datamodel/types_test.go

• Updated TestHasContainerd to expect true for all runtime configurations

• Updated test cases for Docker, empty string, and unexpected runtime values

• Updated TestKubernetesConfig_RequiresDocker to expect false for all cases

• Added explanatory comments about Kubernetes 1.24 Docker removal

• Regenerated all snapshot test data via make generate

• All Go tests pass successfully with new Docker-removed logic

The following kubelet flags were part of dockershim and are no longer valid:

• --cni-bin-dir: CNI binary directory

• --cni-cache-dir: CNI cache directory

• --cni-conf-dir: CNI configuration directory

• --docker-endpoint: Docker endpoint socket

• --image-pull-progress-deadline: Image pull progress deadline

• --network-plugin: Network plugin type

• --network-plugin-mtu: Network plugin MTU

• Before: Conditional logic checked ContainerRuntime config to decide between Docker and containerd

• After: Containerd is always used as the container runtime

• Private Registry Auth: Moved from docker login to containerd registry configuration

The following Docker/Moby-related code remains but is no longer called:

• installMoby() function in parts/linux/cloud-init/artifacts/ubuntu/cse_install_ubuntu.sh
• removeMoby() function in parts/linux/cloud-init/artifacts/ubuntu/cse_install_ubuntu.sh
• ensureRunc() function still exists (used by containerd)

These can be removed in a follow-up cleanup PR if desired.

• ✅ All Go unit tests pass

• ✅ Datamodel tests updated and passing

• ✅ Test data regenerated successfully

• ✅ Shellcheck validation passes (warnings are pre-existing style issues unrelated to this change)

• Kubernetes 1.24 removed dockershim: https://kubernetes.io/blog/2022/05/03/dockershim-historical-context/

• Docker/containerd migration: https://kubernetes.io/docs/tasks/administer-cluster/migrating-from-dockershim/

This change:

• Simplifies the codebase by removing Docker-specific logic
• Aligns with Kubernetes 1.24+ which only supports containerd (and CRI-compatible runtimes)
• Reduces maintenance burden by removing deprecated code paths
• Has no functional impact on AKS nodes as Docker has not been supported since Kubernetes 1.24

---

Which issue(s) this PR fixes:

Fixes #

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version
• commits are GPG signed and Github marks them as verified

Special notes for your reviewer:

This removes support for Docker runtime configurations. All clusters must use containerd (which has been the default and only supported runtime since Kubernetes 1.24).

Release note:

none

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf CI / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Oct 14, 2025, 4:31 PM

[awesomenix]

@microsoft-github-policy-service agree

[awesomenix]

Main pipeline is green this PR is ready for merge
https://msazure.visualstudio.com/CloudNativeCompute/_build/results?buildId=140175512&view=logs&s=69285b21-1299-5bfb-1bce-5b813df3e8eb