Getting the Container configuration of a Docker image using the registry API - docker

Question

In a CLI, I can can do docker inspect --type image {some_image} and part of the answer is:
"ContainerConfig": {
"Hostname": "4beccaca9c40",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
],
"Cmd": [
"/bin/sh",
"-c",
"#(nop) ",
"CMD [\"/bin/sh\" \"-c\" \"cat /marker\"]"
],
"ArgsEscaped": true,
"Image": "sha256:111ecb4a6197242745f0d74c2ca4e377cfe4a1686b33160d3a8df3d3d1baea58",
"Volumes": null,
"WorkingDir": "",
"Entrypoint": null,
"OnBuild": null,
"Labels": {
"key1": "LabelValue1-L2",
"version": "1.2.0"
}
},
The registry API defines an answer type of
application/vnd.docker.container.image.v1+json: Container config JSON
but I cannot relate that to a specific API. When I use it with the ../manifests/.. URL I receive the answer in the default format (application/vnd.docker.distribution.manifest.v1+json)(this also happens if I try to use the "fat manifest" format).
Is this configuration information available somewhere?
The registry is the standard registry image pulled a couple of days ago (says "Created": "2018-01-10T01:22:39.470942376Z")

Answer 1

So, what is required is:
A first call to https://{registry}/v2/{imageName}/manifests/{tag} with an Accept header set to application/vnd.docker.distribution.manifest.v2+json
This returns a JSON, where config.mediaType is set to the content type of the V1 manifest (which is always application/vnd.docker.container.image.v1+json as far as I can tell).
a second call to https://{registry}/v2/{imageName}/manifests/{tag} with an Accept header set to the content-type obtained above (same URL, only the Accept changes).
This returns a JSON, where the member history is a list, and each member of this list has a single v1Compatibility attribute which is a string which can be re-parsed as a JSON.