Teardown Kubernetes Cluster

For every node do:

$ kubectl drain las1 --delete-emptydir-data --force --ignore-daemonsets
⋮
node/las1 drained
$ kubectl delete node las1
node "las1" deleted

You may need to mannully delete/uninstall something like Deployments/Daemonsets.

After all nodes are deleted from the cluster, run sudo kubeadm reset on each node.