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Gadgets as OCI artifacts

Intro TODO

Specifications​

The Open Container Initiative defines the Image Format Specification. This specification was initially defined for container images but it is extended to store other artifacts, see Guidance for Artifacts Authors.

Architectures​

Inspektor Gadget supports multi architecture artifacts. The following architectures are supported:

  • amd64
  • arm64

ArtifactType​

Media type: application/vnd.gadget.v1+binary

This indicates the manifest is a Gadget. It follows the guidelines in: https://github.com/opencontainers/image-spec/blob/main/manifest.md#guidelines-for-artifact-usage.

Gadget metadata​

Media type: application/vnd.gadget.config.v1+yaml

This contains the gadget metadata.

Image layers and media types​

Each architecture can contain several layers, but each layer must have a different media type among the following:

  • application/vnd.gadget.ebpf.program.v1+binary
  • application/vnd.gadget.wasm.program.v1+binary
  • application/vnd.gadget.btfgen.v1+binary

The ebpf layer​

There must be exactly one layer with the ebpf media type. It must not be empty. Its content must be a valid ELF file. See gadget eBPF API.

The wasm layer​

There must be at most one layer with the wasm media type. If present, it must not be empty and it must be a valid wasm file. See WASM API.

The btfgen layer​

btfgen is used to enable running eBPF programs on kernels that don't provide BTF information. A gadget image can contain at most one btfgen layer. This layer must contain the generated BTF files in a tarball following the same folder structure of btfhub-archive.

Image annotations​

OCI images can have annotations at different levels:

  • index
  • manifest
  • config
  • layer

Inspektor Gadget automatically adds the following annotations at the manifest and config levels:

  • org.opencontainers.image.*: defined by OCI Image Format
    • title
    • description
    • url
    • documentation
    • source
    • created