kubectl shows error You must be logged in to the server (Unauthorized) after Kubernetes upgrade

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Published on June 30th 2020 - Listed in Kubernetes Containers Rancher


After a Kubernetes cluster was upgraded from K8s 1.13 to 1.15, local kubectl commands could not be executed anymore and failed with the following error:

$ kubectl get nodes
error: You must be logged in to the server (Unauthorized)

This was working fine just before the upgrade and the correct kube config is being used - could it be related to the new version? Let's compare the client (kubectl) and the server versions of Kubernetes:

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"6", GitVersion:"v1.6.0", GitCommit:"fff5156092b56e6bd60fff75aad4dc9de6b6ef37", GitTreeState:"clean", BuildDate:"2017-03-28T16:36:33Z", GoVersion:"go1.7.5", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"15", GitVersion:"v1.15.12", GitCommit:"e2a822d9f3c2fdb5c9bfbe64313cf9f657f0a725", GitTreeState:"clean", BuildDate:"2020-05-06T05:09:48Z", GoVersion:"go1.12.17", Compiler:"gc", Platform:"linux/amd64"}

The local kubectl command seems pretty outdated, still running with 1.6. Is that it? Is a local client update sufficient? On the local machine, kubectl was upgraded to 1.18:

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.4", GitCommit:"c96aede7b5205121079932896c4ad89bb93260af", GitTreeState:"clean", BuildDate:"2020-06-17T11:41:22Z", GoVersion:"go1.13.9", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"15", GitVersion:"v1.15.12", GitCommit:"e2a822d9f3c2fdb5c9bfbe64313cf9f657f0a725", GitTreeState:"clean", BuildDate:"2020-05-06T05:09:48Z", GoVersion:"go1.12.17", Compiler:"gc", Platform:"linux/amd64"}

And the kubectl commands work again:

$ kubectl get nodes
NAME             STATUS   ROLES                      AGE    VERSION
192.168.253.12   Ready    controlplane,etcd,worker   199d   v1.15.12
192.168.253.13   Ready    controlplane,etcd,worker   199d   v1.15.12
192.168.253.14   Ready    controlplane,etcd,worker   14h    v1.15.12


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Ming from wrote on Nov 23rd, 2020:

this article realy help me very much.^_^