Kubernetes is a free, open-source distribution and also known as k8s. It is utilized for automating deployment, management, and scaling of containerized software and applications. It provides different components for container management such as nodes, control plane, pods, and Kubernetes deployment. With the help of Kubernetes,  the developers can easily automate the operational task, roll back the changes, and monitor and scale the containerized applications and software.

In this blog, we will explain:

• • What is Kubernetes Deployment?
  • Why Creating Deployment is Better than Creating Pods?
  • What is a ReplicaSet in Deployment?
  • What is the “kubectl create deployment” Command?
  • Prerequisite: Install kubectl and minikube
  • How to Create Kubernetes Deployment Using “kubectl create deployment” Command?
  • How to Run Replicas in Kubernetes Deployment Using “kubectl create deployment” Command?
  • How Does ReplicaSet Work to Control Kubernetes Deployment?
  • Conclusion

What is Kubernetes Deployment?

The Kubernetes Deployment is referred to as a resource object that provides declarative instruction and updates to its major elements such as Pods, ReplicaSet, and containerized applications. The Kubernetes Deployment permits the developer to describe the containerized application such as image, number of pods, port, replicas, and so on. The one major reason why Kubernetes is better than Docker is that it offers us auto-healing and auto-scaling properties and these states are achievable due to Kubernetes Deployment.

In “auto-healing” mechanism is a test automation technique that tests its running object and in case of any error occurrence, implements the best match for correction, and applies the fix to match the actual state with the desired state. In “auto-scaling” service scales the application’s workload automatically.

Why Creating Deployment is Better than Creating Pods?

Kubernetes deployment permits the developer to easily keep a group of the same pods running with a common configuration. In contrast, while creating a pod, users are required to create and run the pod separately. In deployment, if one pod is deleted or terminated, it will automatically be recreated and started due to an auto-healing mechanism. But if pods are directly executing without deployment, in case of error, users are required to recreate and run the pod manually.

What is a ReplicaSet in Deployment?

When the developer created the deployment, three major components were generated and ReplicaSet is one of them. The ReplicaSet is a controller of deployment and is responsible for running the specified number of Pods within a deployment. In case, if one pod is deleted, the ReplicaSet quickly instructs to regenerate the new pod to match the actual state of the pods with the desired state. It is majorly responsible for providing declarative updates to pods.

What is the “kubectl create deployment” Command?

The “kubectl create deployment” is a command of the Kubectl tool that is used to create and start the Kubernetes deployment. Then deployment instructs Kubernetes how to create and update instances of your application.

Syntax

 
Option

The “kubectl create deployment” command supports different options to provide an extra layer of functionality and to give extra instruction to deploy instances of an application. The options supported by the “kubectl create deployment” command is given below in tabular form:

Prerequisite: Install kubectl and minikube

To start Kubernetes Deployment in the Kubernetes cluster, first, install the below given tools on the system:

• • Kubectl Tool: Kubectl is a Kubernetes command line tool that is utilized to control, manage, and operate a Kubernetes cluster and its components such as Kubernetes Deployment.
  • Minikube Tool: Minikube is an implementation system for Kubernetes that provides or creates a virtual machine on the system to start the Kubernetes cluster. It can execute single-node clusters and is mostly used by beginners or for testing purposes.

To get started with Kubernetes and to install essential components like “kubectl” and “minikube”, go through our linked “Get Started With Kubernetes and Kubectl” article.

How to Create Kubernetes Deployment Using “kubectl create” Command?

The Kubernetes deployment can be created by applying the Yaml manifest or by the “kubectl create deployment” command. To create the Kubernetes deployment using the “kubectl create deployment” command, follow the below-provided demonstration.

Step 1: Run PowerShell

First, launch the Windows PowerShell with administrative privileges from the Start menu. The administrative privileges are required because minikube starts the Kubernetes cluster on the virtual machine by using HyperV:

Step 2: Start Kubernetes Cluster

To start the Kubernetes cluster, utilize the “minikube start” command:

 

Step 3: Get Kubernetes Nodes

Next, access the Kubernetes nodes to check if the cluster is started or not using the “kubectl get nodes” command:

 

Step 4: Create Kubernetes Deployment

Create a new Kubernetes deployment in the cluster through the “kubectl create deployment <deployment-name> –image=<image-name>” command. For demonstration, we have created “nginx-deployment” that will execute the Nginx application in a pod using the “nginx:stable-perl” image:

 

Step 5: Get Kubernetes Deployment, ReplicaSet and Pod

The “kubectl create deployment” command will create three components Deployment, ReplicaSet, and Pod. To access the Kubernetes deployments, run the “kubectl get deploy” command:

 
Here, you can see “nginx-deployment” is available in the Kubernetes cluster:

The ReplicaSet is the controller of deployment that ensures the application in pods is executing error-free and repairs the breakpoints. To access the ReplicaSet, utilize the “kubectl get rs” command:

 
Here, the ReplicaSet shows the desired number of pods and current running pods:

The pod is a smaller unit of the Kubernetes cluster that runs the containerized application. To access the Kubernetes pods, use the “kubectl get pods” command. Here the “-o” option is used to specify the output format. To view the Pod IP address, we have used the “wide” format:

 

Step 6: Log in to Kubernetes Cluster

To access the application running in a container, first, access the Kubernetes cluster using the “minikube ssh” command:

 

Step 7: Access Application Running in Kubernetes Deployment

After that, utilize the “curl” command along with the Pod IP address to access the containerized application:

How to Run Replicas in Kubernetes Deployment Using “kubectl create deployment” Command?

Creating Kubernetes Deployment is better than running Pod as it can run and manage a group of pods at one time by creating Pod replicas. To run replicas in Kubernetes deployment using the “kubectl create deployment” command, follow the below instructions.

Step 1: Create Kubernetes Deployment

First, create a deployment using the “kubectl create deployment” command along with the “–replicas” option. The value of the “replicas” option will specify the desired number of pods that should be managed and run by ReplicaSet:

 

Step 2: Get Kubernetes Deployment, ReplicaSet, and Pods

Now, access the Kubernetes deployment using the “kubectl get deploy” command:

 
Here, you can see deployment is showing the ready, up-to-date, and available number of pods:

Use the below command to access ReplicaSet information. You can see that ReplicaSet is showing the status of the desired number of pods and currently executing pods:

 

Similarly, to access the running pods, use the below command:

 
The output indicates that the Kubernetes deployment is successfully executing the desired number of Pods replicas in the Kubernetes cluster:

How ReplicaSet Works to Control Kubernetes Deployment?

The ReplicaSet is responsible for running the desired number of Pods within a deployment. If one pod is broken down or deleted, it will automatically recreate the pod to match the current status of the Pods with the desired state. This mechanism is actually implementing the auto-healing technique. For demonstration, follow the below instructions.

Step 1: View Live Kubernetes Pods

First, view the Pods status live using the “kubectl get pods -w” command. Also, note the name of the pod that will be broken or deleted:

 

Step 2: Delete a Pod

Next, open another PowerShell terminal and try to delete the second pod using the “kubectl delete pods <pod-name>” command:

 
The output shows that we have successfully deleted the pod:

Now, open the PowerShell window where the pod’s status is live. Here, you can see when we deleted the Pod, the ReplicaSet automatically created and executed the new pod to match the current pods status to the desired status:

We have covered the method for creating Kubernetes Deployment using the “kubectl create deployment” command.

Conclusion

To create the Kubernetes Deployment using the “kubectl create deployment” command, first, install the essential tools like minikube and kubectl. After that, run the new Kubernetes cluster using minikube. Now, create a new deployment using the “kubectl create deployment <deployment-name> –image=<image-name>” command. After that, view the Kubernetes deployment, ReplicaSet, and Pods using the “kubectl get all” command. This article has illustrated how to create the Kubernetes Deployment using the “kubectl create deployment” command.