cinder/api-ref/source/v2/samples/volume-image-metadata-set-request.json

{
    "os-set_image_metadata": {
        "metadata": {
            "image_id": "521752a6-acf6-4b2d-bc7a-119f9148cd8c",
            "image_name": "image",
            "kernel_id": "155d900f-4e14-4e4c-a73d-069cbf4541e6",
            "ramdisk_id": "somedisk"
        }
    }
}