Issue : Failed to pull image : rpc error: code = 2 desc = unknown blob

Introduction

When you are deploying an image, which is hosted on a private registry, to a kubernetes (k8s) cluster with windows nodes… Then you might get the following error ;

Failed to pull image “kvaes.azurecr.io/kvaes2017:v1“: rpc error: code = 2 desc = unknown blob
Error syncing pod, skipping: failed to “StartContainer” for “private-reg-container” with ErrImagePull: “rpc error: code = 2 desc = unknown blob”

 

Context

So what did my setup look like?

  • Orchestrator : Kubernetes for Windows (Azure Container Service)
  • Registry : Private (Azure Container Registry)
  • Image : Windows Nano Based

 

Technical Check

Let’s deploy two pods…

The first I’ll deploy via yaml, which is basically the example from the kubernetes docs on pulling an image from a private repo

Now the second one is an adaptation of the example flow from the Azure Container Service documentation ;

Now let’s see how that one went…

The first one failed, and the second one passed! What was the difference?

 "nodeSelector": {
    "beta.kubernetes.io/os": "windows"
    }

Apparently this one forces the switch to “windows container mode” (or something like that…). As it seems very similar to the following thread

 

TL;DR

When deploying windows containers to a kubernetes cluster. be sure to the set the “nodeSelector” or you might end up with errors on pulling the image.

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