<p>I’ve been learning about Kubernetes using Kelsey Hightower’s excellent kubernetes-the-hard-way-guide.</p>

<p>Using this guide I’ve installed v1.12 on GCE. Everything works perfectly apart from kubectl exec:</p>

<pre><code>$ kubectl exec -it shell-demo – /bin/bash --kubeconfig=/root/certsconfigs/admin.kubeconfig
error: unable to upgrade connection: Forbidden (user=kubernetes, verb=create, resource=nodes, subresource=proxy)
</code></pre>

<p>Note that I have set <code>KUBECONFIG=/root/certsconfigs/admin.kubeconfig</code>.</p>

<p>Apart from exec all other kubectl functions work as expected with this <code>admin.kubeconfig</code> file, so from that I deduce it valid for use with my cluster.</p>

<p>I’m pretty sure I have made a beginners mistake somewhere, but if somebody could advise where I have gone away, I should be most grateful.</p>

<p>TIA</p>

<p>Shaun</p>

<p>I have double checked that no <code>.kube/config</code> file exists anywhere on my master controller:</p>

<pre><code>root@controller-1:/root/deployment/kubernetes# kubectl get pods
NAME READY STATUS
shell-demo 1/1 Running 0 23m
</code></pre>

<p>Here is the output with -v8:</p>

<pre><code>root@controller-1:/root/deployment/kubernetes# kubectl -v8 exec -it shell-demo – /bin/bash
I1118 15:18:16.898428 11117 loader.go:359] Config loaded from file /root/certsconfigs/admin.kubeconfig
I1118 15:18:16.899531 11117 loader.go:359] Config loaded from file /root/certsconfigs/admin.kubeconfig
I1118 15:18:16.900611 11117 loader.go:359] Config loaded from file /root/certsconfigs/admin.kubeconfig
I1118 15:18:16.902851 11117 round_trippers.go:383] GET ://127.0.0.1:6443/api/v1/namespaces/default/pods/shell-demo
I1118 15:18:16.902946 11117 round_trippers.go:390] Request Headers:
I1118 15:18:16.903016 11117 round_trippers.go:393] Accept: application/json, /
I1118 15:18:16.903091 11117 round_trippers.go:393] User-Agent: kubectl/v1.12.0 (linux/amd64) kubernetes/0ed3388
I1118 15:18:16.918699 11117 round_trippers.go:408] Response Status: 200 OK in 15 milliseconds
I1118 15:18:16.918833 11117 round_trippers.go:411] Response Headers:
I1118 15:18:16.918905 11117 round_trippers.go:414] Content-Type: application/json
I1118 15:18:16.918974 11117 round_trippers.go:414] Content-Length: 2176
I1118 15:18:16.919053 11117 round_trippers.go:414] Date: Sun, 18 Nov 2018 15:18:16 GMT
I1118 15:18:16.919218 11117 request.go:942] Response Body: {“kind”:“Pod”,“apiVersion”:“v1”,“metadata”:{“name”:“shell-demo”,“namespace”:“default”,“selfLink”:"/api/v1/namespaces/default/pods/shell-demo",“uid”:“99f320f8-eb42-11e8-a053-42010af0000b”,“resourceVersion”:“13213”,“creationTimestamp”:“2018-11-18T14:59:51Z”},“spec”:{“volumes”:[{“name”:“shared-data”,“emptyDir”:{}},{“name”:“default-token-djprb”,“secret”:{“secretName”:“default-token-djprb”,“defaultMode”:420}}],“containers”:[{“name”:“nginx”,“image”:“nginx”,“resources”:{},“volumeMounts”:[{“name”:“shared-data”,“mountPath”:"/usr/share/nginx/html"},{“name”:“default-token-djprb”,“readOnly”:true,“mountPath”:"/var/run/secrets/kubernetes.io/serviceaccount"}],“terminationMessagePath”:"/dev/termination-log",“terminationMessagePolicy”:“File”,“imagePullPolicy”:“Always”}],“restartPolicy”:“Always”,“terminationGracePeriodSeconds”:30,“dnsPolicy”:“ClusterFirst”,“serviceAccountName”:“default”,“serviceAccount”:“default”,“nodeName”:“worker-1”,“securityContext”:{},“schedulerName”:“default-scheduler”,“tolerations”:[{“key”:"node.kubernet [truncated 1152 chars]
I1118 15:18:16.925240 11117 round_trippers.go:383] POST …
error: unable to upgrade connection: Forbidden (user=kubernetes, verb=create, resource=nodes, subresource=proxy)
</code></pre>

user3115872
<p>According to your logs,the connection between kubectl and the apiserver is fine, and is being authenticated correctly.</p>
<p>To satisfy an exec request, the apiserver contacts the kubelet running the pod, and that connection is what is being forbidden.</p>
<p>Your kubelet is configured to authenticate/authorize requests, and the apiserver credential is not authorized to make the exec request against the kubelet's API.</p>
<p>Based on the forbidden message, your apiserver is authenticating as the &quot;kubernetes&quot; user to the kubelet.</p>
<p>You can grant that user full permissions to the kubelet API with the following command:</p>
<p><code>kubectl create clusterrolebinding apiserver-kubelet-admin --user=kubernetes --clusterrole=system:kubelet-api-admin</code></p>
<p>See the following docs for more information</p>
<blockquote>
<p><a href="https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-authentication-authorization/#overview" rel="nofollow noreferrer">https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-authentication-authorization/#overview</a></p>
<p><a href="https://kubernetes.io/docs/reference/access-authn-authz/rbac/#other-component-roles" rel="nofollow noreferrer">https://kubernetes.io/docs/reference/access-authn-authz/rbac/#other-component-roles</a></p>
</blockquote>
