Ubuntu 20.04
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Kubernetes : Remove Nodes
2020/08/19
 
Remove Nodes from existing Kubernetes Cluster.
This example is based on the environment like follows and remove a Node [node03.srv.world] from it.
-----------+---------------------------+--------------------------+-------------+
           |                           |                          |             |
       eth0|10.0.0.30              eth0|10.0.0.51             eth0|10.0.0.52    |
+----------+-----------+   +-----------+----------+   +-----------+----------+  |
|   [ dlp.srv.world ]  |   | [ node01.srv.world ] |   | [ node02.srv.world ] |  |
|      Master Node     |   |      Worker Node     |   |      Worker Node     |  |
+----------------------+   +----------------------+   +----------------------+  |
                                                                                |
------------------------------------------------------------------+-------------+
                                                                  |
                                                              eth0|10.0.0.53
                                                      +-----------+----------+
                                                      | [ node03.srv.world ] |
                                                      |      Worker Node     |
                                                      +----------------------+

[1] Remove a Node on Master Node.
# prepare to remove a target node

# --ignore-daemonsets ⇒ ignore pods in DeamonSet

# --delete-local-data ⇒ ignore pods that has emptyDir volumes

# --force ⇒ also remove pods that was created as a pod, not as deployment or others

root@dlp:~#
kubectl drain node03.srv.world --ignore-daemonsets --delete-local-data --force

node/node03.srv.world drained

# verify a few minutes later

root@dlp:~#
kubectl get nodes node03.srv.world

NAME               STATUS                     ROLES    AGE   VERSION
node03.srv.world   Ready,SchedulingDisabled   <none>   28m   v1.18.8

# run delete method

root@dlp:~#
kubectl delete node node03.srv.world

node "node03.srv.world" deleted

root@dlp:~#
kubectl get nodes

NAME               STATUS   ROLES    AGE    VERSION
dlp.srv.world      Ready    master   166m   v1.18.8
node01.srv.world   Ready    <none>   162m   v1.18.8
node02.srv.world   Ready    <none>   161m   v1.18.8
[2] On the removed Node, Reset kubeadm settings.
root@node03:~#
kubeadm reset

[reset] WARNING: Changes made to this host by 'kubeadm init' or 'kubeadm join' will be reverted.
[reset] Are you sure you want to proceed? [y/N]: y
[preflight] Running pre-flight checks
W0819 14:22:09.113836   20286 removeetcdmember.go:79] [reset] No kubeadm config, using etcd pod spec to get data directory
[reset] No etcd config found. Assuming external etcd
[reset] Please, manually reset etcd to prevent further issues
[reset] Stopping the kubelet service
[reset] Unmounting mounted directories in "/var/lib/kubelet"
[reset] Deleting contents of config directories: [/etc/kubernetes/manifests /etc/kubernetes/pki]
[reset] Deleting files: [/etc/kubernetes/admin.conf /etc/kubernetes/kubelet.conf /etc/kubernetes/bootstrap-kubelet.conf /etc/kubernetes/controller-manager.conf /etc/kubernetes/scheduler.conf]
[reset] Deleting contents of stateful directories: [/var/lib/kubelet /var/lib/dockershim /var/run/kubernetes /var/lib/cni]

The reset process does not clean CNI configuration. To do so, you must remove /etc/cni/net.d

The reset process does not reset or clean up iptables rules or IPVS tables.
If you wish to reset iptables, you must do so manually by using the "iptables" command.

If your cluster was setup to utilize IPVS, run ipvsadm --clear (or similar)
to reset your system's IPVS tables.

The reset process does not clean your kubeconfig files and you must remove them manually.
Please, check the contents of the $HOME/.kube/config file.
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