Applying Kubernetes Configurations with kubectl apply

Using kubectl apply allows Kubernetes configurations to be applied or updated based on the YAML or JSON files provided. This command is essential for deploying new resources, updating existing configurations, or even reverting to a previous state if needed.

Here are several examples showcasing the versatility of kubectl apply:

Example 1: Deploying a new Pod from a YAML file:

kubectl apply -f pod.yaml

This command applies the Pod configuration defined in pod.yaml. To verify, use kubectl get pods to see if the Pod is running.

Example 2: Updating a Deployment with a new image:

kubectl apply -f deployment.yaml

If deployment.yaml specifies a new Docker image, this command updates the Deployment accordingly. Check the Deployment status with kubectl get deployment.

Example 3: Applying a Service definition:

kubectl apply -f service.yaml

Creates or updates a Kubernetes Service based on the configuration in service.yaml. Confirm the Service’s creation with kubectl get services.

Example 4: Adding a ConfigMap to the cluster:

kubectl apply -f configmap.yaml

This applies the ConfigMap defined in configmap.yaml. Verify its existence with kubectl get configmap.

Example 5: Applying a PersistentVolumeClaim:

kubectl apply -f pvc.yaml

Creates or updates a PersistentVolumeClaim as defined in pvc.yaml. Check its status using kubectl get pvc.

Example 6: Deploying a CronJob:

kubectl apply -f cronjob.yaml

This command schedules a new CronJob based on the configuration provided in cronjob.yaml. Use kubectl get cronjob to see its execution status.

Example 7: Applying a HorizontalPodAutoscaler:

kubectl apply -f hpa.yaml

Creates or updates a HorizontalPodAutoscaler defined in hpa.yaml. Verify its creation using kubectl get hpa.

Example 8: Deploying a StatefulSet:

kubectl apply -f statefulset.yaml

Applies the StatefulSet configuration from statefulset.yaml. Check its deployment status with kubectl get statefulset.

Example 9: Updating a Namespace:

kubectl apply -f namespace.yaml

If namespace.yaml modifies Namespace attributes, this command updates it. Ensure changes with kubectl get namespace.

Example 10: Applying a Role and RoleBinding:

kubectl apply -f role.yaml -f rolebinding.yaml

Applies both Role and RoleBinding configurations defined in respective files. Verify creation with kubectl get roles and kubectl get rolebindings.

Also check similar articles.

Diffing Kubernetes Configurations with kubectl diff
Listing Kubernetes Events with kubectl events
Troubleshooting Kubernetes with kubectl debug
Managing Kubernetes Authorization with kubectl auth
Copy Files to and from Kubernetes Containers with kubectl cp