How to use the command 'kubectl create' (with examples)

The kubectl create command is used in Kubernetes to create a new resource. It can create a resource from a file or from stdin. This command is commonly used for creating deployments, services, namespaces, and other resources in a Kubernetes cluster.

Use case 1: Create a resource using the resource definition file

Code:

kubectl create -f path/to/file.yml

Motivation: Using a resource definition file allows you to declaratively define the desired state of your resource (such as a deployment or service) and use it to create the resource. This can be useful for maintaining a version-controlled configuration and automating resource creation.

Explanation:

• kubectl create: The base command for creating a resource.
• -f path/to/file.yml: Specifies the file path to the resource definition file.

Example output:

deployment.apps/my-deployment created

Use case 2: Create a resource from stdin

Code:

kubectl create -f -

Motivation: This use case allows you to create a resource by providing its definition through stdin. This can be useful when you want to dynamically generate the resource definition or when the resource definition is not stored in a file.

Explanation:

• kubectl create: The base command for creating a resource.
• -f -: Specifies that the resource definition will be provided through stdin.

Example output:

deployment.apps/my-deployment created

Use case 3: Create a deployment

Code:

kubectl create deployment deployment_name --image=image

Motivation: Deployments are commonly used in Kubernetes for managing the rollout of containerized applications. This use case allows you to create a deployment with a specified name and container image.

Explanation:

• kubectl create: The base command for creating a resource.
• deployment deployment_name: Specifies the resource type (deployment) and the name of the deployment.
• --image=image: Specifies the container image to use for the deployment.

Example output:

deployment.apps/my-deployment created

Use case 4: Create a deployment with replicas

Code:

kubectl create deployment deployment_name --image=image --replicas=number_of_replicas

Motivation: Specifying the number of replicas allows you to control the scalability of your application. This use case allows you to create a deployment with a specified number of replicas.

Explanation:

• kubectl create: The base command for creating a resource.
• deployment deployment_name: Specifies the resource type (deployment) and the name of the deployment.
• --image=image: Specifies the container image to use for the deployment.
• --replicas=number_of_replicas: Specifies the number of replicas to create for the deployment.

Example output:

deployment.apps/my-deployment created

Use case 5: Create a service

Code:

kubectl create service service_type service_name --tcp=port:target_port

Motivation: Services in Kubernetes are used to expose applications running in the cluster to other services within or outside the cluster. This use case allows you to create a service with a specified type, name, and port mapping.

Explanation:

• kubectl create: The base command for creating a resource.
• service service_type service_name: Specifies the resource type (service), the type of the service (such as ClusterIP or NodePort), and the name of the service.
• --tcp=port:target_port: Specifies the mapping between the port exposed by the service and the target port of the application.

Example output:

service/my-service created

Use case 6: Create a namespace

Code:

kubectl create namespace namespace_name

Motivation: Namespaces are used to logically divide a Kubernetes cluster into multiple virtual clusters. This use case allows you to create a namespace with a specified name.

Explanation:

• kubectl create: The base command for creating a resource.
• namespace namespace_name: Specifies the resource type (namespace) and the name of the namespace.

Example output:

namespace/my-namespace created

Conclusion:

The kubectl create command is a versatile command in Kubernetes that allows you to create various resources. Whether you want to create a deployment, service, namespace, or any other resource, this command provides the flexibility to define the desired state and create the resource in your cluster.