Error:
Unable to connect to the server: x509: certificate signed by unknown authority
Fix:
unset KUBECONFIG
export KUBECONFIG=/etc/kubernetes/admin.conf
mv $HOME/.kube $HOME/.kube.bak
mkdir $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config