Image pull fails with "unknown blob" error for ImageStreams using a pull-through cache with an external registry in OpenShift Container Platform 4.

Solution In Progress - Updated -

Issue

An ImagePullBackoff error is observed for pods consuming an ImageStream that references an external container registry with referencePolicy: type: Local. The OpenShift Container Platform registry logs show err.detail="unknown blob" and Background mirroring failed. This issue often occurs when the external registry (e.g., Artifactory) provides inconsistent HTTP responses, specifically returning HTTP 200 OK to a HEAD request but HTTP 404 Not Found to a subsequent GET request for a non-existent image layer (blob).

Environment

  • Red Hat OpenShift Container Platform [RHOCP]
  • Integrated OpenShift Image Registry configured pointing to an external registry (e.g., JFrog Artifactory).

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