Using Init Containers in Kubernetes

Introduction

Init containers are a great way to customize container startup. This lab will allow you to test your knowledge of init containers by using them to solve problems in an existing Kubernetes cluster.

Solution

Log in to the provided lab server using the credentials provided:

ssh cloud_user@<PUBLIC_IP_ADDRESS>

Create a Sample Pod That Uses an Init Container to Delay Startup

1. Open the pod descriptor file:

   vi pod.yml
   

2. Add an init container (at the same level as containers in the file) to delay startup until the shipping-svc service is available:

   spec:
     ...
     initContainers:
     - name: shipping-svc-check
       image: busybox:1.27
       command: ['sh', '-c', 'until nslookup shipping-svc; do echo waiting for shipping-svc; sleep 2; done']
   

3. Save and exit the file by pressing Escape followed by :wq.

4. Create the pod:

   kubectl create -f pod.yml
   

5. Check the status of the pod:

   kubectl get pods
   

   It should remain in the Init status.

Test Your Setup by Creating the Service and Verifying the Pod Starts Up

1. Create the service from the shipping-svc.yml file:

   kubectl create -f shipping-svc.yml
   

2. Check the status of your pod again:

   kubectl get pods
   

   It should enter the Running status after about a minute.