106 lines
4.9 KiB
Markdown
106 lines
4.9 KiB
Markdown
# OCI Image Manifest Specification
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There are three main goals of the Image Manifest Specification.
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The first goal is content-addressable images, by supporting an image model where the image's configuration can be hashed to generate a unique ID for the image and its components.
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The second goal is to allow multi-architecture images, through a "fat manifest" which references image manifests for platform-specific versions of an image.
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In OCI, this is codified in a [Manifest List](manifest-list.md).
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The third goal is to be translatable to the [OCI Runtime Specification](https://github.com/opencontainers/runtime-spec).
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This section defines the `application/vnd.oci.image.manifest.v1+json` [media type](media-types.md).
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For the media type(s) that this is compatible with see the [matrix](media-types.md#compatibility-matrix).
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# Image Manifest
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Unlike the [Manifest List](manifest-list.md), which contains information about a set of images that can span a variety of architectures and operating systems, an image manifest provides a configuration and set of layers for a single container image for a specific architecture and operating system.
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## *Image Manifest* Property Descriptions
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- **`schemaVersion`** *int*
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This REQUIRED property specifies the image manifest schema version.
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For this version of the specification, this MUST be `2` to ensure backward compatibility with older versions of Docker. The value of this field will not change. This field MAY be removed in a future version of the specification.
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- **`mediaType`** *string*
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This property is *reserved* for use, to [maintain compatibility][matrix].
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When used, this field contains the media type of this document, which differs from the [descriptor](descriptor.md#properties) use of `mediaType`.
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- **`config`** *[descriptor](descriptor.md)*
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This REQUIRED property references a configuration object for a container, by digest.
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Beyond the [descriptor requirements](descriptor.md#properties), the value has the following additional restrictions:
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- **`mediaType`** *string*
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This [descriptor property](descriptor.md#properties) has additional restrictions for `config`.
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Implementations MUST support at least the following media types:
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- [`application/vnd.oci.image.config.v1+json`](config.md)
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Manifests concerned with portability SHOULD use one of the above media types.
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- **`layers`** *array of objects*
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Each item in the array MUST be a [descriptor](descriptor.md).
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The array MUST have the base layer at index 0.
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Subsequent layers MUST then follow in stack order (i.e. from `layers[0]` to `layers[len(layers)-1]`).
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The final filesystem layout MUST match the result of [applying](layer.md#applying) the layers to an empty directory.
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The [ownership, mode, and other attributes](layer.md#file-attributes) of the initial empty directory are unspecified.
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Beyond the [descriptor requirements](descriptor.md#properties), the value has the following additional restrictions:
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- **`mediaType`** *string*
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This [descriptor property](descriptor.md#properties) has additional restrictions for `layers[]`.
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Implementations MUST support at least the following media types:
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- [`application/vnd.oci.image.layer.v1.tar`](layer.md)
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- [`application/vnd.oci.image.layer.v1.tar+gzip`](layer.md#gzip-media-types)
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- [`application/vnd.oci.image.layer.nondistributable.v1.tar`](layer.md#non-distributable-layers)
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- [`application/vnd.oci.image.layer.nondistributable.v1.tar+gzip`](layer.md#gzip-media-types)
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Manifests concerned with portability SHOULD use one of the above media types.
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Entries in this field will frequently use the `+gzip` types.
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- **`annotations`** *string-string map*
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This OPTIONAL property contains arbitrary metadata for the image manifest.
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This OPTIONAL property MUST use the [annotation rules](annotations.md#rules).
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See [Pre-Defined Annotation Keys](annotations.md#pre-defined-annotation-keys).
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## Example Image Manifest
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*Example showing an image manifest:*
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```json,title=Manifest&mediatype=application/vnd.oci.image.manifest.v1%2Bjson
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{
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"schemaVersion": 2,
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"config": {
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"mediaType": "application/vnd.oci.image.config.v1+json",
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"size": 7023,
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"digest": "sha256:b5b2b2c507a0944348e0303114d8d93aaaa081732b86451d9bce1f432a537bc7"
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},
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"layers": [
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{
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"mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
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"size": 32654,
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"digest": "sha256:e692418e4cbaf90ca69d05a66403747baa33ee08806650b51fab815ad7fc331f"
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},
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{
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"mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
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"size": 16724,
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"digest": "sha256:3c3a4604a545cdc127456d94e421cd355bca5b528f4a9c1905b15da2eb4a4c6b"
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},
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{
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"mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
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"size": 73109,
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"digest": "sha256:ec4b8955958665577945c89419d1af06b5f7636b4ac3da7f12184802ad867736"
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}
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],
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"annotations": {
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"com.example.key1": "value1",
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"com.example.key2": "value2"
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}
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}
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```
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