How to Use Kubectl Cordon Command

Kubernetes is a popular container orchestration system that has become the de-facto standard in modern software development. One of the most important features of Kubernetes is the ability to control the scheduling of workloads on a cluster.

Kubectl is a command-line interface for interacting with Kubernetes, and it provides a variety of commands that allow you to control your Kubernetes cluster.

In this article, we'll be discussing how to use the kubectl cordon command.

Introduction to Kubectl Cordon

The kubectl cordon command is used to mark a node as unschedulable. This means that no new pods will be scheduled on that node, but existing pods will continue to run until they are terminated or moved elsewhere. This is useful when you need to perform maintenance on a node or when you want to drain a node before decommissioning it.

Using the Kubectl Cordon Command

The syntax for using the kubectl cordon command is as follows:

kubectl cordon [node-name]

Where node-name is the name of the node that you want to mark as unschedulable.

Step-by-Step Instructions

Here are the step-by-step instructions to use the kubectl cordon command:

1. First, you need to have kubectl installed on your system. You can install it using the following command:

curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/

2. Once kubectl is installed, you can use the following command to verify that it is working correctly:

kubectl version

3. To mark a node as unschedulable, use the following command:

kubectl cordon [node-name]

Replace [node-name] with the name of the node that you want to mark as unschedulable.

4. To verify that the node has been marked as unschedulable, use the following command:

kubectl get nodes

This will show you a list of all nodes in your cluster, along with their status. The node that you marked as unschedulable should now have the SchedulingDisabled condition.

5. To mark the node as schedulable again, use the following command:

kubectl uncordon [node-name]

Replace [node-name] with the name of the node that you want to mark as schedulable again.

Additional Examples

Here are some additional examples of how to use the kubectl cordon command:

1. To mark all nodes as unschedulable, use the following command:

kubectl cordon --all

2. To mark a node as unschedulable and immediately evict all pods running on that node, use the following command:

kubectl cordon [node-name] --ignore-daemonsets --force

Replace [node-name] with the name of the node that you want to mark as unschedulable.

In this article, we've discussed how to use the kubectl cordon command. This command is useful when you need to perform maintenance on a node or when you want to drain a node before decommissioning it. By following the step-by-step instructions and examples provided in this article, you should now be able to use the kubectl cordon command effectively.

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That's it for this post. Keep practicing and have fun. Leave your comments if any.