Ubuntu 22.04
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Kubernetes : Remove Nodes
2022/11/03
 
Remove Nodes from existing Kubernetes Cluster.
This example is based on the environment like follows and remove a Node [snode03.srv.world] from it.
-----------+---------------------------+--------------------------+--------------+
           |                           |                          |              |
       eth0|10.0.0.25              eth0|10.0.0.71             eth0|10.0.0.72     |
+----------+-----------+   +-----------+-----------+   +-----------+-----------+ |
|  [ ctrl.srv.world ]  |   |  [snode01.srv.world]  |   |  [snode02.srv.world]  | |
|     Control Plane    |   |      Worker Node      |   |      Worker Node      | |
+----------------------+   +-----------------------+   +-----------------------+ |
                                                                                 |
------------+--------------------------------------------------------------------+
            |
        eth0|10.0.0.73
+-----------+-----------+
|  [snode03.srv.world]  |
|      Worker Node      |
+-----------------------+

[1] Remove a Node on Master Node.
# prepare to remove a target node
# --ignore-daemonsets ⇒ ignore pods in DeamonSet
# --delete-emptydir-data ⇒ ignore pods that has emptyDir volumes
# --force ⇒ also remove pods that was created as a pod, not as deployment or others

root@ctrl:~#
kubectl drain snode03.srv.world --ignore-daemonsets --delete-emptydir-data --force

Warning: ignoring DaemonSet-managed Pods: kube-system/calico-node-762x8, kube-system/kube-proxy-lm25n
node/snode03.srv.world drained

# verify a few minutes later

root@ctrl:~#
kubectl get nodes snode03.srv.world

NAME                STATUS                     ROLES    AGE   VERSION
snode03.srv.world   Ready,SchedulingDisabled   <none>   14m   v1.25.3

# run delete method

root@ctrl:~#
kubectl delete node snode03.srv.world

node "snode03.srv.world" deleted

root@ctrl:~#
kubectl get nodes

NAME                STATUS   ROLES           AGE   VERSION
ctrl.srv.world      Ready    control-plane   26h   v1.25.3
snode01.srv.world   Ready    <none>          25h   v1.25.3
snode02.srv.world   Ready    <none>          25h   v1.25.3
[2] On the removed Node, Reset kubeadm settings.
root@snode03:~#
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
W1103 04:37:53.839439    7438 removeetcdmember.go:85] [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 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]

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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