server@b56ab63ee631

This is not an image: it is a BuildKit attestation entry of a multi-arch index.

docker buildx stores the attestations it generates as an extra entry of the index, with the placeholder platform unknown/unknown, describing the variant 0acfa3239f0a. It appears whenever a build records provenance — on by default since Docker 24 / buildx 0.11 — or an SBOM (--sbom=true); images built with plain docker build or with --provenance=false have no such entry. docker pull never fetches it by itself; docker buildx imagetools inspect and docker sbom read it.

This entry contains: SLSA provenance v1 (25.5 KiB) — no SBOM: the build did not pass --sbom=true.

It belongs to server:main-22cd85a, server@332da90dff0d, so it cannot be deleted on its own: removing it would break that index. Delete the tag or the index and the next prune untagged run (or a retention policy) removes this entry; garbage collection reclaims its bytes.

To build without attestation entries: docker buildx build --provenance=false --sbom=false …

docker pull chicor.ee/tund/server@sha256:b56ab63ee631344f9908e0f7ee91b83f4897325ec2d5f8721b5567c03ef04361

Digest: b56ab63ee631344f9908
Media type: application/vnd.oci.image.manifest.v1+json
Platform: none — attestation entry (unknown/unknown)
Total size: 25.5 KiB
Pushed: Oct 6, 2026byGitHub Actions · tund/github-ci

Cargo plan

1 layer25.5 KiB

#	Instruction	Digest	Shared	Size
1	`—`	b922ec557908	unique	25.5 KiB

{
  "schemaVersion": 2,
  "mediaType": "application/vnd.oci.image.manifest.v1+json",
  "artifactType": "application/vnd.docker.attestation.manifest.v1+json",
  "config": {
    "mediaType": "application/vnd.oci.empty.v1+json",
    "digest": "sha256:44136fa355b3678a1146ad16f7e8649e94fb4fc21fe77e8310c060f61caaff8a",
    "size": 2,
    "data": "e30="
  },
  "layers": [
    {
      "mediaType": "application/vnd.in-toto+json",
      "digest": "sha256:b922ec557908948016ed2b5e13000cf0ab5ab59ce7e336af908d59a652172f6b",
      "size": 26132,
      "annotations": {
        "in-toto.io/predicate-type": "https://slsa.dev/provenance/v1"
      }
    }
  ],
  "subject": {
    "mediaType": "application/vnd.oci.image.manifest.v1+json",
    "digest": "sha256:0acfa3239f0a20012e2d5d6bf61b720b0721b4845b04b7d90a4283beb8506171",
    "size": 1056
  }
}