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Kubernetes : Remove Nodes2024/06/07


Remove Nodes from existing Kubernetes Cluster.

This example is based on the cluster environment like follows.
It removes [node03.srv.world (] from this cluster.

+----------------------+   +----------------------+
|  [ ctrl.srv.world ]  |   |   [ dlp.srv.world ]  |
|     Manager Node     |   |     Control Plane    |
+-----------+----------+   +-----------+----------+
        eth0|             eth0|
            |                          |
            |                          |                          |
        eth0|             eth0|             eth0|
+-----------+----------+   +-----------+----------+   +-----------+----------+
| [ node01.srv.world ] |   | [ node02.srv.world ] |   | [ node03.srv.world ] |
|     Worker Node#1    |   |     Worker Node#2    |   |     Worker Node#3    |
+----------------------+   +----------------------+   +----------------------+

[1] Work on Manager node.
kubectl get nodes

NAME               STATUS   ROLES           AGE     VERSION
dlp.srv.world      Ready    control-plane   3h40m   v1.30.1
node01.srv.world   Ready    <none>          3h35m   v1.30.1
node02.srv.world   Ready    <none>          3h34m   v1.30.1
node03.srv.world   Ready    <none>          7m44s   v1.30.1

# prepare to remove a target node
# --ignore-daemonsets ⇒ ignore pods in DaemonSet
# --delete-emptydir-data ⇒ ignore pods that has emptyDir volumes
# --force ⇒ also remove pods that was created as a pod, not as deployment or others

kubectl drain node03.srv.world --ignore-daemonsets --delete-emptydir-data --force

node/node03.srv.world cordoned
Warning: ignoring DaemonSet-managed Pods: kube-system/calico-node-gl4k8, kube-system/kube-proxy-8c2hq
node/node03.srv.world drained

# verify a few minutes later

kubectl get nodes node03.srv.world

NAME               STATUS                     ROLES    AGE    VERSION
node03.srv.world   Ready,SchedulingDisabled   <none>   9m6s   v1.30.1

# run delete method

kubectl delete node node03.srv.world

node "node03.srv.world" deleted

kubectl get nodes

NAME               STATUS   ROLES           AGE     VERSION
dlp.srv.world      Ready    control-plane   3h42m   v1.30.1
node01.srv.world   Ready    <none>          3h37m   v1.30.1
node02.srv.world   Ready    <none>          3h36m   v1.30.1
[2] On the removed Node, Reset kubeadm settings.
kubeadm reset

W0607 03:32:56.950681    7883 preflight.go:56] [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
W0607 03:32:57.968829    7883 removeetcdmember.go:106] [reset] No kubeadm config, using etcd pod spec to get data directory
[reset] Deleted contents of the etcd data directory: /var/lib/etcd
[reset] Stopping the kubelet service
[reset] Unmounting mounted directories in "/var/lib/kubelet"
[reset] Deleting contents of directories: [/etc/kubernetes/manifests /var/lib/kubelet /etc/kubernetes/pki]
[reset] Deleting files: [/etc/kubernetes/admin.conf /etc/kubernetes/super-admin.conf /etc/kubernetes/kubelet.conf /etc/kubernetes/bootstrap-kubelet.conf /etc/kubernetes/controller-manager.conf /etc/kubernetes/scheduler.conf]

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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