Exercise Kubernetes Deployment

1. Introduction

In this lab exercise, we'll cover essential Kubernetes deployment tasks. You'll create a deployment, verify its details, scale the number of pods, upgrade the application image, and finally, delete the deployment.

2. Imperative vs. Declarative

Imperative: Directly create, update, or delete resources using commands.
Declarative: Describe desired resource states using configuration files (YAML) and apply them.

3. Creating the Deployment

3.1 Declarative Method

Create a YAML specification for the deployment:
- Name: my-deployment
- Container: my-container with image nginx:1.14.2
- Number of replicas: 3
Create a file named deployment.yaml:

vi deployment.yaml

Add the following content to deployment.yaml:

    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: my-deployment
    spec:
      replicas: 3
      selector:
        matchLabels:
          app: my-app
      template:
        metadata:
          labels:
            app: my-app
        spec:
          containers:
            - name: my-container
              image: nginx:1.14.2
              ports:
                - containerPort: 80

(Note: This file describes the desired state of your application.)

References

3.2 Imperative Method

Alternatively, you can create the same deployment imperatively using the following command:

kubectl create deployment my-deployment --image=nginx --replicas=3

This command directly creates the deployment.

(Note: This command may fail since the deployment named my-deployment already exist. Either change the name of the deployment or delete the existing deployment then recreate it with Imperative Method.) (To delete deployment refer the session ## 6. Deleting Deployment)Deleting Deployment

4. Verifying Deployment

4.1 Get Deployment Details

To list all deployments:
```
kubectl get deployments
```
To describe a specific deployment (e.g., "my-deployment"):
```
kubectl describe deployment my-deployment
```

4.2 ReplicaSet and Pods

A deployment automatically creates a ReplicaSet, which manages identical Pods.
To view ReplicaSets:
```
kubectl get rs
```
To see Pods under a specific deployment:
```
kubectl get pods -o wide
```

5. Scaling and Upgrading

5.1 Scale Pods

To scale the number of Pods in a deployment (e.g., "my-deployment") to 5:
```
kubectl scale deployment my-deployment --replicas=5
```

5.2 Rollout Status

To verify the rollout status:

kubectl rollout status deployment my-deployment

5.3 Upgrade Image Version

Update the image version in your deployment YAML file.
Apply the changes:
```
kubectl apply -f deployment.yaml
```
(Note: Image upgrades will be explained in the next exercise.)

5.4 Scale Down

To scale down to 3 replica:

kubectl scale deployment my-deployment --replicas=3

To scale down to 1 replica:

kubectl scale deployment my-deployment --replicas=1

6. Deleting Deployment

6.1 Using Imperative Command

To delete a deployment (e.g., "my-deployment"):
```
kubectl delete deployment my-deployment
```

6.2 Using Definition File

To delete the deployment using the definition file (deployment.yaml):
```
kubectl delete -f deployment.yaml
```

7. References

PreviousExercise: Advanced Pod Commands and Details NextAdvanced Kubernetes Deployment Exercise

Last updated 13 days ago

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