124 lines
5.2 KiB
Markdown
124 lines
5.2 KiB
Markdown
# OCI Image Index Specification
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The image index is a higher-level manifest which points to specific [image manifests](manifest.md), ideal for one or more platforms.
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While the use of an image index is OPTIONAL for image providers, image consumers SHOULD be prepared to process them.
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This section defines the `application/vnd.oci.image.index.v1+json` [media type](media-types.md).
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For the media type(s) that this document is compatible with, see the [matrix][matrix].
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## *Image Index* 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.
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The value of this field will not change.
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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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- **`manifests`** *array of objects*
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This REQUIRED property contains a list of [manifests](manifest.md) for specific platforms.
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While this property MUST be present, the size of the array MAY be zero.
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Each object in `manifests` includes a set of [descriptor properties](descriptor.md#properties) with the following additional properties and restrictions:
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- **`mediaType`** *string*
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This [descriptor property](descriptor.md#properties) has additional restrictions for `manifests`.
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Implementations MUST support at least the following media types:
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- [`application/vnd.oci.image.manifest.v1+json`](manifest.md)
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Image indexes concerned with portability SHOULD use one of the above media types.
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Future versions of the spec MAY use a different mediatype (i.e. a new versioned format).
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An encountered `mediaType` that is unknown SHOULD be safely ignored.
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- **`platform`** *object*
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This OPTIONAL property describes the minimum runtime requirements of the image.
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This property SHOULD be present if its target is platform-specific.
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- **`architecture`** *string*
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This REQUIRED property specifies the CPU architecture.
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Image indexes SHOULD use, and implementations SHOULD understand, values [supported by runtime-spec's `platform.arch`][runtime-platform2].
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- **`os`** *string*
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This REQUIRED property specifies the operating system.
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Image indexes SHOULD use, and implementations SHOULD understand, values [supported by runtime-spec's `platform.os`][runtime-platform2].
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- **`os.version`** *string*
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This OPTIONAL property specifies the version of the operating system targeted by the referenced blob.
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Implementations MAY refuse to use manifests where `os.version` is not known to work with the host OS version.
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Valid values are implementation-defined. e.g. `10.0.14393.1066` on `windows`.
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- **`os.features`** *array of strings*
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This OPTIONAL property specifies an array of strings, each specifying a mandatory OS feature (for example on Windows `win32k`).
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- **`variant`** *string*
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This OPTIONAL property specifies the variant of the CPU.
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Image indexes SHOULD use, and implementations SHOULD understand, values listed in the following table.
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When the variant of the CPU is not listed in the table, values are implementation-defined and SHOULD be submitted to this specification for standardization.
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| ISA/ABI | `architecture` | `variant` |
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|-----------------|----------------|-------------|
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| ARM 32-bit, v6 | `arm` | `v6` |
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| ARM 32-bit, v7 | `arm` | `v7` |
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| ARM 32-bit, v8 | `arm` | `v8` |
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| ARM 64-bit, v8 | `arm64` | `v8` |
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- **`features`** *array of strings*
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This property is RESERVED for future versions of the specification.
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- **`annotations`** *string-string map*
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This OPTIONAL property contains arbitrary metadata for the image index.
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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 Index
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*Example showing a simple image index pointing to image manifests for two platforms:*
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```json,title=Image%20Index&mediatype=application/vnd.oci.image.index.v1%2Bjson
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{
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"schemaVersion": 2,
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"manifests": [
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{
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"mediaType": "application/vnd.oci.image.manifest.v1+json",
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"size": 7143,
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"digest": "sha256:e692418e4cbaf90ca69d05a66403747baa33ee08806650b51fab815ad7fc331f",
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"platform": {
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"architecture": "ppc64le",
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"os": "linux"
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}
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},
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{
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"mediaType": "application/vnd.oci.image.manifest.v1+json",
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"size": 7682,
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"digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270",
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"platform": {
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"architecture": "amd64",
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"os": "linux"
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}
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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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[runtime-platform2]: https://github.com/opencontainers/runtime-spec/blob/v1.0.0-rc3/config.md#platform
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[matrix]: media-types.md#compatibility-matrix
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