Image Manifest

The Ocre Container Image Manifest (application/vnd.oci.image.manifest.v1+json) defines the structure and contents of an Ocre container. It provides a standardized way to organize, configure, and execute container elements within the Ocre runtime, providing configuration and layers for a single cohesive container image.

The manifest references all elements that comprise the container image. This includes the following elements:

• Configuration: Metadata defining container execution, including properties, variables, and permissions.
• WebAssembly Module: Standard WebAssembly executable code that runs in the container runtime.
• Blobs (Optional): Additional resources that can be referenced by the application, such as images, binary data, or AI/ML models.

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Manifest Structure

The manifest format follows the OCI Image Manifest specification, and while this format typically supports multiple architectures and operating systems, Ocre containers are fixed to the Wasi configuration. Additionally, every Ocre container must include a manifest file (application/vnd.oci.image.manifest.v1+json) with a matching mediaType.

Example

{
  "schemaVersion": 2,
  "mediaType": "application/vnd.oci.image.manifest.v1+json",
  "config": {
      "mediaType": "application/vnd.wasm.config.v0+json",
      "digest": "sha256:55a98fff5a9a7bef217678f2669ad89816875df55af51b6d1c23a5f9393234e3",
      "size": 196
  },
  "layers": [
      {
          "mediaType": "application/wasm",
          "digest": "sha256:71cb138990af165c4baf0c43361e5c055ed60a5d2632ee547597be56dcfa07e2",
          "size": 2397
      }
  ]
}

Manifest Elements

Elements within the manifest are defined as follows:

Element	Type	Required	Description
schemaVersion	int	Yes	Specifies the image manifest schema version; per the OCI Image Spec this MUST be 2
mediaType	string	Yes	Specifies the type of this manifest file; for Ocre containers, this MUST be application/vnd.oci.image.manifest.v1+json
config	descriptor object	Yes	References the configuration object for this container image; schema follows the OCI Content Descriptor schema; mediaType must be set to application/vnd.wasm.config.v0+json
layers	array	Yes	Specifies the list of elements that comprise this container image; each layer is a descriptor; one and only one layer MUST be of type application/wasm

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Learn More

To understand how container configuration works in detail, see the Image Configuration guide, which explains how metadata, environment variables, and execution parameters are defined for Ocre containers.