server@5d51779a2b8f

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 22f872ed0f6f. 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 (22.6 KiB) — no SBOM: the build did not pass --sbom=true.

It belongs to server:main-031cb68, server@aeea0e5c406f, 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@sha256:5d51779a2b8fbcde54489c685b6e2151e4732c6318ee1bb2580d784f033f5414

Digest: 5d51779a2b8fbcde5448
Media type: application/vnd.oci.image.manifest.v1+json
Platform: none — attestation entry (unknown/unknown)
Total size: 22.6 KiB
Pushed: Oct 13, 2026byGitHub Actions · tund/github-ci

Cargo plan

1 layer22.6 KiB

#	Instruction	Digest	Shared	Size
1	`—`	1d395b2d247f	unique	22.6 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": "sha256:1d395b2d247f6525d09bdf9bbfe1e7faac271a6f8a2c12b1014c55919a431a85",
      "size": 23188,
      "annotations": {
        "in-toto.io/predicate-type": "https://slsa.dev/provenance/v1"
      }
    }
  ],
  "subject": {
    "mediaType": "application/vnd.oci.image.manifest.v1+json",
    "digest": "sha256:22f872ed0f6f70e5128f3f2ff0aab3edd1fb4daf97d39a32624da093dd872a96",
    "size": 1056
  }
}