• Relates to Support alternative runtimes with cri-dockerd #45030
• Relates to Support for alternative runtimes Mirantis/cri-dockerd#111 (comment)

Kubernetes only permits RuntimeClass values which are valid lowercase RFC 1123 labels, which disallows the period character. This prevents cri-dockerd from being able to support configuring alternative shimv2 runtimes for a pod as shimv2 runtime names must contain at least one period character.

- What I did

• Added support for configuring named shimv2 runtimes in daemon.json so that runtime names can be aliased to Kubernetes-compatible names.
• Added support for setting options for shimv2 runtimes in daemon.json.

- How I did it

I took heavy inspiration from cri-containerd configuration and its implementation. The names of the new daemon runtime config fields have been selected to correspond with the equivalent field names in cri-containerd's configuration so that users can more easily follow documentation from the runtime vendor written for cri-containerd and apply it to daemon.json.

- How to verify it

Create a /etc/docker/daemon.json containing

{
	"runtimes": {
		"custom": {
			"runtime-type": "io.containerd.runc.v2",
			"options": {
			       "BinaryName": "/usr/local/bin/doesnotexist"
			}
		}
	}
}

and (re)start the daemon. Try running a container with that runtime and examine the error message to see if the BinaryName option was respected.

$ docker run --rm --runtime custom alpine ls
docker: Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: unable to retrieve OCI runtime error (open /var/run/docker/containerd/daemon/io.containerd.runtime.v2.task/moby/0c07ce57ea72bc26d0ffa0d1501506329fb15054e56072c076f0efc56f7eb342/log.json: no such file or directory): fork/exec /usr/local/bin/doesnotexist: no such file or directory: unknown.

- Description for the changelog

• Alternative runtimes can now be configured in daemon.json, enabling runtime names to be aliased and options to be passed.

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