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Part 3: Using Deployments

This is Part 3 of a multi-part, self-paced quick start exercise.

Note

This exercise requires MicroK8s. If you do not have these already installed and running, see "Prerequisites".

What Will You Do

In part 3, you will:

  • Use Deployments to update your pods.

Estimated Time

Estimated time for this exercise is 10 minutes. Watch a video of the exercise below.

Using Deployments

A Deployment provides declarative updates for Pods and ReplicaSets. This exercise will focus on Deployments.

Deployment YAML file

Create a deployment using a YAML file, which is a configuration file. You could create a YAML file from the command line, but for this exercise, you can just use a text editor. Or you can download the deployment YAML file from from this public Git repository.

  1. Open the Terminal.
  2. Navigate to the Downloads folder. 
    cd ./Downloads
  3. Use the following command to create an empty YAML file in your Downloads folder. 
    touch deployment.yaml
  4. Use the nano text editor in the Terminal. 
    nano deployment.yaml
  5. Copy and paste the configuration below into the text editor.
  6. Press Cmd + X, then type Y and press Return to save the deployment.yaml file.
  1. Open the command prompt.
  2. Navigate to the Downloads folder. 
    cd ./Downloads
  3. Use the following command to create an empty YAML file in your Downloads folder. 
    copy NUL deployment.yaml
  4. Open the deployment.yaml file with a text editor.
  5. Copy and paste the configuration below into the text editor.
  6. Save the deployment.yaml file.
  1. Open the Terminal.
  2. Navigate to the Downloads folder. 
    cd ./Downloads
  3. Use the following command to create an empty YAML file in your Downloads folder. 
    touch deployment.yaml
  4. Use the nano text editor in the Terminal. 
    nano deployment.yaml
  5. Copy and paste the configuration below into the text editor.
  6. Press Cmd + X, then type Y and press Return to save the deployment.yaml file.

Add a Deployment

  1. In the Terminal or Command Prompt, list the resources in the current namespace. There may not be any resources listed. 
    microk8s kubectl get deployment -o wide
  2. Use the deployment.yaml file to manage your pods. 
    microk8s kubectl create -f deployment.yaml
  3. List resources in the current namespace. You now have a test-deployment using the python-http-server container. 
    microk8s kubectl get deployment -o wide
  4. View a list of replicasets. 
    microk8s kubectl get replicaset

  5. View the list of pods. Copy the name of one of the pods. Make sure the test-deployment pods are ready. 

    microk8s kubectl get pods

    Get Pods

  6. Access the pod. Replace pod-name with the name of the pod. 

    microk8s kubectl exec -it pod-name -- bash

  7. Run a curl command. You should see the response included in the YAML file, including the name for the pod.

    curl http://localhost

    Deployment Response

  8. Exit the pod. 

    exit

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: test-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: test-pod
  template:
    metadata:
      labels:
        app: test-pod
    spec:
      containers:
      - name: python-http-server
        image: python:2.7
        command: ["/bin/bash"]
        args: ["-c", "echo \" Hello from $(hostname)\" > index.html; python -m SimpleHTTPServer 80"]
        ports:
        - name: http
          containerPort: 80