Run a Stateless Application Using a Deployment

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

Before you begin

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

Play with Kubernetes

Your Kubernetes server must be at or later than version v1.9. To check the version, enter .

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:1.14.2 Docker image:

application/deployment.yaml

Create a Deployment based on the YAML file:

kubectl apply -f https://k8s.io/examples/application/deployment.yaml

Display information about the Deployment:

kubectl describe deployment nginx-deployment

Name:     nginx-deployment
Namespace:    default
CreationTimestamp:  Tue, 30 Aug 2016 18:11:37 -0700
Labels:     app=nginx
Annotations:    deployment.kubernetes.io/revision=1
Selector:   app=nginx
Replicas:   2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType:   RollingUpdate
MinReadySeconds:  0
Pod Template:
  Labels:       app=nginx
  Containers:
    nginx:
    Image:              nginx:1.14.2
    Port:               80/TCP
    Environment:        <none>
    Mounts:             <none>
Conditions:
  Type          Status  Reason
  ----          ------  ------
  Available     True    MinimumReplicasAvailable
  Progressing   True    NewReplicaSetAvailable
OldReplicaSets:   <none>
NewReplicaSet:    nginx-deployment-1771418926 (2/2 replicas created)
No events.

List the Pods created by the deployment:
```
kubectl get pods -l app=nginx
```
The output is similar to this:
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 1.16.1.

application/deployment-update.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
    matchLabels:
      app: nginx
  replicas: 2
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.16.1 # Update the version of nginx from 1.14.2 to 1.16.1
        ports:
        - containerPort: 80

kubectl apply -f https://k8s.io/examples/application/deployment-update.yaml

Watch the deployment create pods with new names and delete the old pods:
```
kubectl get pods -l app=nginx
```

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:

application/deployment-scale.yaml

Apply the new YAML file:

kubectl apply -f https://k8s.io/examples/application/deployment-scale.yaml

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

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 using a .

What’s next

Learn more about .