Exercise Kubernetes Deployment

Table of Contents

1. Introduction

2. Imperative vs. Declarative

3. Creating the Deployment

   • 3.1 Declarative Method

   • 3.2 Imperative Method

4. Verifying Deployment

   • 4.1 Get Deployment Details

   • 4.2 ReplicaSet and Pods

5. Scaling and Upgrading

   • 5.1 Scale Pods

   • 5.2 Rollout Status

   • 5.3 Upgrade Image Version

   • 5.4 Scale Down

6. Deleting Deployment

   • 6.1 Using Imperative Command

   • 6.2 Using Definition File

7. References

8. Deployment Definition File

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

1. Create a YAML specification for the deployment:

   • Name: my-deployment

   • Container: my-container with image nginx:1.14.2

   • Number of replicas: 3

2. 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

1. Update the image version in your deployment YAML file.

2. 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

• Kubernetes Documentation

• My Blog