website/docs/tasks/run-application/run-stateless-application-deployment.md

title
Run a Stateless Application Using a Deployment

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This page shows how to run an application using a Kubernetes Deployment object.

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• Create an nginx deployment.
• Use kubectl to list information about the deployment.
• Update the deployment.

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Creating and exploring an nginx deployment

You can run an application by creating a Kubernetes Deployment object, and you can describe a Deployment in a YAML file. For example, this YAML file describes a Deployment that runs the nginx:1.7.9 Docker image:

{% include code.html language="yaml" file="deployment.yaml" ghlink="/docs/tasks/run-application/deployment.yaml" %}

1. Create a Deployment based on the YAML file:

   kubectl create -f https://k8s.io/docs/tasks/run-application/deployment.yaml
   

2. Display information about the Deployment:

   kubectl describe deployment nginx-deployment
   
    user@computer:~/kubernetes.github.io$ kubectl describe deployment nginx-deployment
    Name:     nginx-deployment
    Namespace:    default
    CreationTimestamp:  Tue, 30 Aug 2016 18:11:37 -0700
    Labels:     app=nginx
    Selector:   app=nginx
    Replicas:   2 updated | 2 total | 2 available | 0 unavailable
    StrategyType:   RollingUpdate
    MinReadySeconds:  0
    RollingUpdateStrategy:  1 max unavailable, 1 max surge
    Conditions:
      Type          Status  Reason
      ----          ------  ------
      Available     True    MinimumReplicasAvailable
    OldReplicaSets:   <none>
    NewReplicaSet:    nginx-deployment-1771418926 (2/2 replicas created)
    No events.
   

3. List the pods created by the deployment:

   kubectl get pods -l app=nginx
   
    NAME                                READY     STATUS    RESTARTS   AGE
    nginx-deployment-1771418926-7o5ns   1/1       Running   0          16h
    nginx-deployment-1771418926-r18az   1/1       Running   0          16h
   

4. Display information about a pod:

   kubectl describe pod <pod-name>
   

   where <pod-name> is the name of one of your pods.

Updating the deployment

You can update the deployment by applying a new YAML file. This YAML file specifies that the deployment should be updated to use nginx 1.8.

{% include code.html language="yaml" file="deployment-update.yaml" ghlink="/docs/tutorials/stateless-application/deployment-update.yaml" %}

1. Apply the new YAML file:

   kubectl apply -f https://k8s.io/docs/tutorials/stateless-application/deployment-update.yaml
   

2. Watch the deployment create pods with new names and delete the old pods:

   kubectl get pods -l app=nginx
   

Scaling the application by increasing the replica count

You can increase the number of pods in your Deployment by applying a new YAML file. This YAML file sets replicas to 4, which specifies that the Deployment should have four pods:

{% include code.html language="yaml" file="deployment-scale.yaml" ghlink="/docs/tutorials/stateless-application/deployment-scale.yaml" %}

1. Apply the new YAML file:

   kubectl apply -f https://k8s.io/docs/tutorials/stateless-application/deployment-scale.yaml
   

2. Verify that the Deployment has four pods:

   kubectl get pods -l app=nginx
   

   The output is similar to this:

    NAME                               READY     STATUS    RESTARTS   AGE
    nginx-deployment-148880595-4zdqq   1/1       Running   0          25s
    nginx-deployment-148880595-6zgi1   1/1       Running   0          25s
    nginx-deployment-148880595-fxcez   1/1       Running   0          2m
    nginx-deployment-148880595-rwovn   1/1       Running   0          2m
   

Deleting a deployment

Delete the deployment by name:

kubectl delete deployment nginx-deployment

ReplicationControllers -- the Old Way

The preferred way to create a replicated application is to use a Deployment, which in turn uses a ReplicaSet. Before the Deployment and ReplicaSet were added to Kubernetes, replicated applications were configured by using a ReplicationController.

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• Learn more about Deployment objects.

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