> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Demo Deployments

> This walkthrough teaches how to convert a ReplicaSet into a Deployment in Kubernetes, covering creation, application, and verification steps.

In this walkthrough, you’ll learn how to convert an existing ReplicaSet into a fully managed **Deployment**. Deployments offer declarative updates, rollbacks, and scaling capabilities—making them the recommended way to run replicas in production. We’ll:

1. Prepare the project structure
2. Create the Deployment manifest
3. Apply the Deployment
4. Verify the rollout and inspect resources

***

## 1. Prepare the directories and files

1. From your project root, create a folder named `deployments`.
2. Inside `deployments`, create a file called `deployment.yaml`.

To see what we’re building on, here’s the reference ReplicaSet we defined earlier:

```yaml theme={null}
# replicaset.yaml (for reference)
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: myapp-replicaset
  labels:
    app: myapp
spec:
  selector:
    matchLabels:
      app: myapp
  replicas: 4
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: nginx
        image: nginx
```

***

## 2. Create the Deployment manifest

Copy the spec from the ReplicaSet into `deployments/deployment.yaml`, then:

* Change `kind` to `Deployment`
* Set `metadata.name` and labels to match your application
* Adjust `replicas` to **3** (or your desired count)

```yaml theme={null}
# deployments/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
  labels:
    tier: frontend
    app: myapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: nginx
        image: nginx
```

<Callout icon="lightbulb" color="#1CB2FE">
  The `selector.matchLabels` field must exactly match the labels on the Pod template. Otherwise, Kubernetes won’t know which Pods belong to this Deployment.
</Callout>

***

## 3. Apply the Deployment

Run:

```bash theme={null}
kubectl apply -f deployments/deployment.yaml
```

Or, if you prefer `create`:

```bash theme={null}
kubectl create -f deployments/deployment.yaml
```

***

## 4. Verify the rollout and inspect resources

You can quickly see the status of your Deployment and its Pods:

| Action                | Command                                        | Description                                  |
| --------------------- | ---------------------------------------------- | -------------------------------------------- |
| List Deployments      | `kubectl get deployments`                      | Show READY, UP-TO-DATE, AVAILABLE columns    |
| List all Pods         | `kubectl get pods`                             | Confirm your Pods are Running                |
| Describe a Deployment | `kubectl describe deployment myapp-deployment` | View events, strategy, and replica counts    |
| List all resources    | `kubectl get all`                              | Get Pods, Services, Deployments, ReplicaSets |

1. **Check the Deployment status**
   ```bash theme={null}
   kubectl get deployments
   ```
   Example output:
   ```text theme={null}
   NAME               READY   UP-TO-DATE   AVAILABLE   AGE
   myapp-deployment   3/3     3            3           10s
   ```

2. **List the Pods**
   ```bash theme={null}
   kubectl get pods
   ```
   Example output:
   ```text theme={null}
   NAME                                    READY   STATUS    RESTARTS   AGE
   myapp-deployment-5d8fcb5b6c-abc         1/1     Running   0          30s
   myapp-deployment-5d8fcb5b6c-def         1/1     Running   0          30s
   myapp-deployment-5d8fcb5b6c-ghi         1/1     Running   0          30s
   ```

3. **Describe the Deployment**
   ```bash theme={null}
   kubectl describe deployment myapp-deployment
   ```
   You’ll see details such as desired vs. available replicas, rollout strategy, and recent events:

<Frame>
  ![The image shows a terminal window displaying Kubernetes deployment details for an application named "myapp," including container information, conditions, and events related to scaling the replica set.](https://kodekloud.com/kk-media/image/upload/v1752873987/notes-assets/images/Docker-Certified-Associate-Exam-Course-Demo-Deployments/kubernetes-myapp-deployment-details.jpg)
</Frame>

4. **View all objects in the namespace**
   ```bash theme={null}
   kubectl get all
   ```
   Example output:
   ```text theme={null}
   NAME                                   READY   STATUS    RESTARTS   AGE
   pod/myapp-deployment-5d8fcb5b6c-abc    1/1     Running   0          1m
   pod/myapp-deployment-5d8fcb5b6c-def    1/1     Running   0          1m
   pod/myapp-deployment-5d8fcb5b6c-ghi    1/1     Running   0          1m

   NAME                     TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
   service/kubernetes       ClusterIP   10.96.0.1      <none>        443/TCP   15m

   NAME                               READY   UP-TO-DATE   AVAILABLE   AGE
   deployment.apps/myapp-deployment   3/3     3            3           1m

   NAME                                          DESIRED   CURRENT   READY   AGE
   replicaset.apps/myapp-deployment-5d8fcb5b6c   3         3         3       1m
   ```

<Callout icon="lightbulb" color="#1CB2FE">
  To roll out updates, modify `spec.template.spec.containers[].image` and run:

  ```bash theme={null}
  kubectl apply -f deployments/deployment.yaml
  ```

  Then track progress with:

  ```bash theme={null}
  kubectl rollout status deployment/myapp-deployment
  ```
</Callout>

***

## Links and References

* [Kubernetes Deployments](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/)
* [kubectl Cheat Sheet](https://kubernetes.io/docs/reference/kubectl/cheatsheet/)
* [Rolling Updates and Rollbacks](https://kubernetes.io/docs/tutorials/kubernetes-basics/update/update-intro/)

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