Difference between OCI image manifest and Docker V2.2 image manifest

Question

I have a requirement of converting an OCI image manifest to Docker v2.2 image format and vice versa. But I am not able to find any difference between the two , is there any actual difference or they are same ?

Answer 1

Docker Image Manifest V 2, Schema 2

Registry image manifests define the components that make up an image on a container registry (see section on container registries). The more common manifest format we’ll be working with is the Docker Image Manifest V2, Schema 2 (more simply, V2.2). There is also a V2, Schema 1 format that is commonly used but more complicated than V2.2 due to backwards-compatibility reasons against V1.

The V2.2 manifest format is a JSON blob with the following top-level fields:

schemaVersion - 2 in this case

mediaType - application/vnd.docker.distribution.manifest.v2+json

config - descriptor of container configuration blob

layers - list of descriptors of layer blobs, in the same order as the rootfs of the container configuration

Blob descriptors are JSON objects containing 3 fields:

mediaType - application/vnd.docker.container.image.v1+json for a container configuration or application/vnd.docker.image.rootfs.diff.tar.gzip for a layer

size - the size of the blob, in bytes

digest - the digest of the content

Here is an example of a V2.2 manifest format (for the Docker Hub busybox image):

{
  "schemaVersion": 2,
  "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
  "config": {
    "mediaType": "application/vnd.docker.container.image.v1+json",
    "size": 1497,
    "digest": "sha256:3a093384ac306cbac30b67f1585e12b30ab1a899374dabc3170b9bca246f1444"
  },
  "layers": [
    {
      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
      "size": 755724,
      "digest": "sha256:57c14dd66db0390dbf6da578421c077f6de8e88edd0815b4caa94607ba5f4c09"
    }
  ]
}

OCI Image Manifest

The OCI image format is essentially the same as the Docker V2.2 format, with a few differences.

mediaType - must be set to application/vnd.oci.image.manifest.v1+json config.mediaType - must be set to application/vnd.oci.image.config.v1+json

Each object in layers must have mediaType be either application/vnd.oci.image.layer.v1.tar+gzip or application/vnd.oci.image.layer.v1.tar.

Source: https://containers.gitbook.io/build-containers-the-hard-way/#registry-format-oci-image-manifest