Kubectl apply vs Kubectl create?

In the ever-evolving landscape of Kubernetes management, understanding the nuances between various commands is crucial. Two commonly used commands, "kubectl apply" and "kubectl create," might seem interchangeable at first glance, but they serve distinct purposes in the Kubernetes ecosystem. This article aims to demystify the differences between "kubectl apply" and "kubectl create" and guide you on when to use each command effectively.

1. Understanding the Basics:
   Kubernetes, an open-source container orchestration platform, relies heavily on the kubectl command-line tool for interacting with the cluster. "kubectl create" and "kubectl apply" are both used to create resources within a Kubernetes cluster, but they operate in slightly different ways.

2. kubectl create:
   The "kubectl create" command is primarily used for imperative management of Kubernetes resources. It follows a straightforward approach where you provide the complete resource definition directly in the command line, and Kubernetes immediately creates the resource based on that specification.

   kubectl create deployment nginx --image=nginx
   

   In this example, we're creating a deployment named "nginx" with the specified Docker image. The resource definition is provided explicitly in the command.

3. kubectl apply:
   On the other hand, "kubectl apply" is a declarative approach to managing Kubernetes resources. Instead of providing the entire resource definition in the command, you use YAML or JSON files to describe the desired state of the resource, and then apply those files using "kubectl apply."

   kubectl apply -f deployment.yaml
   

   Here, "deployment.yaml" contains the configuration for the deployment, including the image, replicas, and other specifications.

4. When to Use Each Command:

   • kubectl create:

     • Ideal for quick, one-off resource creation.
     • Suitable for situations where the resource definition is simple and can be expressed directly in the command.

   • kubectl apply:

     • Preferred for managing resources over time, especially in production environments.
     • Enables the use of version-controlled configuration files, promoting consistency and reproducibility.

5. Step-by-Step Instructions:

   • Using kubectl create:

     1. Identify the resource you want to create.
     2. Construct the full resource definition in the command line.
     3. Execute the "kubectl create" command.

   • Using kubectl apply:

     1. Create a YAML or JSON file containing the resource definition.
     2. Use "kubectl apply -f filename.yaml" to apply the configuration to the cluster.

6. More Examples:

   • kubectl create:

     • Creating a service: kubectl create service nodeport my-service --tcp=80:8080
     • Adding a secret: kubectl create secret generic my-secret --from-literal=username=admin --from-literal=password=pass123

   • kubectl apply:

     • Applying a persistent volume: kubectl apply -f pv.yaml
     • Deploying a custom resource: kubectl apply -f custom-resource-definition.yaml

In summary, "kubectl create" and "kubectl apply" are both valuable tools in a Kubernetes administrator's toolkit. The choice between them depends on the context of your task and your preference for imperative or declarative resource management. By understanding the distinctions and use cases of each command, you can enhance your efficiency and maintain a more robust Kubernetes environment.