How to gracefully remove a node from Kubernetes?

Question

I want to scale up/down the number of machines to increase/decrease the number of nodes in my Kubernetes cluster. When I add one machine, I’m able to successfully register it with Kubernetes; therefore, a new node is created as expected. However, it is not clear to me how to smoothly shut down the machine later. A good workflow would be:

1. Mark the node related to the machine that I am going to shut down as unschedulable;
2. Start the pod(s) that is running in the node in other node(s);
3. Gracefully delete the pod(s) that is running in the node;
4. Delete the node.

If I understood correctly, even kubectl drain (discussion) doesn't do what I expect since it doesn’t start the pods before deleting them (it relies on a replication controller to start the pods afterwards which may cause downtime). Am I missing something?

How should I properly shutdown a machine?

Answer 1

List the nodes and get the <node-name> you want to drain or (remove from cluster)

kubectl get nodes

1) First drain the node

kubectl drain <node-name>

You might have to ignore daemonsets and local-data in the machine

kubectl drain <node-name> --ignore-daemonsets --delete-local-data

2) Edit instance group for nodes (Only if you are using kops)

kops edit ig nodes

Set the MIN and MAX size to whatever it is -1 Just save the file (nothing extra to be done)

You still might see some pods in the drained node that are related to daemonsets like networking plugin, fluentd for logs, kubedns/coredns etc

3) Finally delete the node

kubectl delete node <node-name>

4) Commit the state for KOPS in s3: (Only if you are using kops)

kops update cluster --yes

OR (if you are using kubeadm)

If you are using kubeadm and would like to reset the machine to a state which was there before running kubeadm join then run

kubeadm reset

Answer 2

On Master Node

Find the node

kubectl get nodes

Drain it

kubectl drain nodetoberemoved

Delete it

kubectl delete node nodetoberemoved

On Worker Node (nodetoberemoved). Remove join/init setting from node

kubeadm reset

Answer 3

Rafael. kubectl drain does work as you describe. There is some downtime, just as if the machine crashed.

Can you describe your setup? How many replicas do you have, and are you provisioned such that you can't handle any downtime of a single replica?

Answer 4

If the cluster is created by kops

1.kubectl drain <node-name>
now all the pods will be evicted

ignore daemeondet:
2.kubectl drain <node-name> --ignore-daemonsets --delete-local-data

3.kops edit ig  nodes-3  --state=s3://bucketname

set max and min value of instance group to 0

4. kubectl delete node

5. kops update cluster --state=s3://bucketname  --yes

Rolling update if required:

6. kops rolling-update cluster  --state=s3://bucketname  --yes

validate cluster:

7.kops validate cluster --state=s3://bucketname

Now the instance will be terminated.

Answer 5

There exists some strange behaviors for me when kubectl drain. Here are my extra steps, otherwise DATA WILL LOST in my case!

Short answer: CHECK THAT no PersistentVolume is mounted to this node. If have some PV, see the following descriptions to remove it.

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When executing kubectl drain, I noticed, some Pods are not evicted (they just did not appear in those logs like evicting pod xxx).

In my case, some are pods with soft anti-affinity (so they do not like to go to the remaining nodes), some are pods of StatefulSet of size 1 and wants to keep at least 1 pod.

If I directly delete that node (using the commands mentioned in other answers), data will get lost because those pods have some PersistentVolumes, and deleting a Node will also delete PersistentVolumes (if using some cloud providers).

Thus, please manually delete those pods one by one. After deleted, kuberentes will re-schedule the pods to other nodes (because this node is SchedulingDisabled).

After deleting all pods (excluding DaemonSets), please CHECK THAT no PersistentVolume is mounted to this node.

Then you can safely delete the node itself :)