How to Use Kubectl Apply Command

Kubectl is a command-line tool used for managing Kubernetes clusters. It is used to deploy, inspect, and manage Kubernetes objects. One of the most commonly used commands in Kubectl is the "apply" command. This article will guide you through the process of using the Kubectl apply command.

What is Kubectl Apply Command?

The Kubectl apply command is used to create, update, or delete Kubernetes objects in a cluster. It allows you to define and apply configuration changes to your Kubernetes objects in a declarative manner. The apply command uses YAML files to define the desired state of your Kubernetes objects.

Step-by-Step Guide to Using Kubectl Apply Command

Follow these steps to use the Kubectl apply command:

Step 1: Install Kubectl

Before using the Kubectl apply command, ensure that you have installed Kubectl on your machine. You can find the installation instructions on the official Kubernetes documentation.

Step 2: Create a YAML file

Create a YAML file that defines the desired state of your Kubernetes object. For example, if you want to create a deployment, your YAML file should include information about the container image, replicas, and any other relevant information.

Step 3: Apply the YAML file

To apply the YAML file, use the following command:

kubectl apply -f <filename>.yaml

Replace <filename> with the name of your YAML file.

Step 4: Check the status of the object

After applying the YAML file, you can check the status of the object using the following command:

kubectl get <object-type>

Replace <object-type> with the type of object you just created. For example, if you created a deployment, you would use "kubectl get deployments".

Step 5: Update the object

To update the object, modify the YAML file and then apply the changes using the "kubectl apply" command again. Kubernetes will automatically update the object to match the new configuration.

Step 6: Delete the object

To delete the object, use the following command:

kubectl delete <object-type> <object-name>

Replace <object-type> with the type of object you want to delete, and <object-name> with the name of the object.

More Examples of Kubectl Apply Command
Here are some more examples of how to use the Kubectl apply command:

• Create a service using a YAML file:

apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector:
    app: my-app
  ports:
  - name: http
    port: 80
    targetPort: 80
  type: LoadBalancer

Apply the YAML file using the "kubectl apply" command.

• Update a deployment:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 3
  template:
    spec:
      containers:
      - name: my-container
        image: my-image:latest

Modify the number of replicas and the container image, and then apply the changes using the "kubectl apply" command again.

The Kubectl apply command is a powerful tool for managing Kubernetes objects in a declarative manner. By following the steps outlined in this article, you can easily create, update, and delete Kubernetes objects using the Kubectl apply command.

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