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.

macOSWindowsUbuntu

Open the Terminal.
Navigate to the Downloads folder.
```
cd ./Downloads
```
Use the following command to create an empty YAML file in your Downloads folder.
```
touch deployment.yaml
```
Use the nano text editor in the Terminal.
```
nano deployment.yaml
```
Copy and paste the configuration below into the text editor.
Press Cmd + X, then type Y and press Return to save the deployment.yaml file.

Open the command prompt.
Navigate to the Downloads folder.
```
cd ./Downloads
```
Use the following command to create an empty YAML file in your Downloads folder.
```
copy NUL deployment.yaml
```
Open the deployment.yaml file with a text editor.
Copy and paste the configuration below into the text editor.
Save the deployment.yaml file.

Open the Terminal.
Navigate to the Downloads folder.
```
cd ./Downloads
```
Use the following command to create an empty YAML file in your Downloads folder.
```
touch deployment.yaml
```
Use the nano text editor in the Terminal.
```
nano deployment.yaml
```
Copy and paste the configuration below into the text editor.
Press Cmd + X, then type Y and press Return to save the deployment.yaml file.

Add a Deployment¶

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
```
Use the deployment.yaml file to manage your pods.
```
microk8s kubectl create -f deployment.yaml
```
List resources in the current namespace. You now have a test-deployment using the python-http-server container.
```
microk8s kubectl get deployment -o wide
```
View a list of replicasets.
```
microk8s kubectl get replicaset
```
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
```
Access the pod. Replace pod-name with the name of the pod.
```
microk8s kubectl exec -it pod-name -- bash
```
Run a curl command. You should see the response included in the YAML file, including the name for the pod.
```
curl http://localhost
```
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