server@f4a3eccbc248

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 a9bac1e9433a. 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@11c11b12304a, 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:f4a3eccbc248d96cb473d030e971048de1757da113e619be1913f2f079cbe62c

Digest: f4a3eccbc248d96cb473
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	`—`	d7a43ee2011b	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:d7a43ee2011b31f07c32c6fff4a1d64c8a73af9444f2092faf77f24400bdbb91",
      "size": 26139,
      "annotations": {
        "in-toto.io/predicate-type": "https://slsa.dev/provenance/v1"
      }
    }
  ],
  "subject": {
    "mediaType": "application/vnd.oci.image.manifest.v1+json",
    "digest": "sha256:a9bac1e9433a6cd22b4f63e56d585d857da84362b57db676930441750d3f39a9",
    "size": 1056
  }
}