Mismatched kubeadm versions & kubeadm join
When joining a cluster with versions of kubeadm
and/ or kubelet
which don't match the master, you get an error like:
[kubelet] Downloading configuration for the kubelet from the "kubelet-config-1.11" ConfigMap in the kube-system namespace
configmaps "kubelet-config-1.11" is forbidden: User "system:bootstrap:tn8mhk" cannot get configmaps in the namespace "kube-system"
This can be fixed by installing matching versions (e.g. apt-cache madison kubeadm
then apt-get install kubeadm=OUTPUT_FROM_APT-CACHE
Use apt-cache policy PACKAGE_NAME
to get the currently installed version on the master.