Below are the details provided for the JSON specs which are required for launching container. These JSON specs are used to create a Docker Compose YAML file in the background, therefore it will have many attributes similar to the Docker Compose YAML.

To make the explanation simple, below is pasted a working spec. The explanation follows subsequently. The keys which begin with an underscore are treated as comments.

{
    "repo_name":"custom-image-c001",
    "tag_name":"latest",
    "_image_file_path":"if image_file_path is empty or not present, then the repo should be available at the docker hub",
    "image_file_path":"/home/example/custom-image-c001.img",
    "container_entry_point":"node",
    "container_cmd":"/home/example/fldr1/sub-fld1/bg.js",
    "container_user":"example",
    "container_volumes":[
        "_ Below entry denotes /home/example/fldr1/sub-fld1 . will be mounted by same name in container",
        "/home/example/fldr1/sub-fld1",
        "_ Below entry denotes /home/example/fldr1/sub-fld2 mounted as /var/nfolder in container",
        "/home/example/fldr1/sub-fld2:/var/nfolder"
    ],
    "_container_port":"optional - port number of the app",
    "container_port":3000,
    "_vhost":"Its an optional entry, buy required if required to be access from the webserver",
    "vhost":"apps.example.com",
    "_vhost_url":"Can be empty or whatever the URL be. It should not be used in any context like regulay, node apps or python apps",
    "vhost_url":"/apps/102",
    "_open_port":"Optional. The port to be opened and which will be mapped to a the container port",
    "open_port":2093
}