Solution Pods optional

In this lesson, you'll explore a hands-on lab that deepens your understanding of Kubernetes pods. We'll start by checking existing pods, create new ones with various images, inspect pod details, and adjust a pod configuration using YAML.

1. Verify Existing Pods

First, examine the current pods running in your Kubernetes cluster by executing:

kubectl get pods

You might see an output similar to this:

kubectl get pods
No resources found in default namespace.

2. Creating a Pod with the Nginx Image

To create a new pod using the Nginx image, use the following command:

kubectl run nginx --image=nginx

The pod creation is confirmed in the output:

pod/nginx created

After creating the pod, run the command again to see all current pods:

kubectl get pods

You might see a list similar to this:

NAME              READY   STATUS              RESTARTS   AGE
nginx             0/1     ContainerCreating   0          17s
newpods-llstt    0/1     ContainerCreating   0          11s
newpods-pnnx8    0/1     ContainerCreating   0          11s
newpods-k87fx    0/1     ContainerCreating   0          11s

Here, several pods have been created and will be examined further.

3. Inspecting Pod Details

To inspect details about one of the newly created pods (for example, newpods-llstt), use:

kubectl describe pod newpods-llstt

This command outputs extensive information such as start time, node assignment, labels, and container details. In the section under "Containers," you should see an entry like:

Containers:
  busybox:
    Container ID:   containerd://b05cd692af1f3b433883f9a8ece19ec2e8c4fcf861aa97ae6a82857ed6037a6d
    Image:          busybox
    ...

The above confirms that the image used in the pod is busybox.

Determine Node Placement

To see which nodes are hosting your pods, run:

kubectl get pods -o wide

Sample output:

NAME             READY   STATUS    RESTARTS   AGE   IP              NODE           NOMINATED NODE   READINESS GATES
SS GATES         1/1     Running   0          2m3s  10.42.0.10     controlplane   <none>           <none>
newpods-pnnx8    1/1     Running   0          2m3s  10.42.0.12     controlplane   <none>           <none>
newpods-llstt    1/1     Running   0          2m3s  10.42.0.11     controlplane   <none>           <none>
newpods-k87fx    1/1     Running   0          2m3s  10.42.0.9      controlplane   <none>           <none>
nginx            1/1     Running   0          2m9s  10.42.0.9      controlplane   <none>           <none>

All listed pods are running on the controlplane node.

4. Working with a Multi-Container Pod (Web App)

Now consider a pod named webapp that includes two containers—one running the nginx image and the other using the agentx image. Check the status of the pods with:

kubectl get pods

You may observe output like the following:

NAME            READY   STATUS             RESTARTS   AGE
newpods-pnnx8   1/1     Running            0          2m33s
newpods-llstt   1/1     Running            0          2m33s
newpods-k87fx   1/1     Running            0          2m33s
nginx           1/1     Running            0          2m39s
webapp          1/2     ImagePullBackOff   0          15s

The READY column uses an X/Y format, where X represents the number of containers ready, and Y is the total containers in the pod. Here, the webapp pod shows that while one container (nginx) is running, the second container (agentx) is not, due to an image pull error.

To further inspect the webapp pod and diagnose the issue, run:

kubectl describe pod webapp

You'll notice that:

• The nginx container is in a Running state.
• The agentx container is in a Waiting state with the reason ErrImagePull, indicating that the image "agentx" could not be pulled from Docker Hub.

5. Deleting the Faulty Web App Pod

Since the webapp pod has an error, remove it using:

kubectl delete pod webapp

The standard output should confirm deletion:

pod "webapp" deleted

6. Creating and Modifying a Redis Pod Using a YAML Definition

Next, you will create a pod named redis using an intentionally incorrect image (redis123) to simulate an error scenario. Although you can use kubectl run to create a pod, it's recommended to define it with a YAML file for better control and maintainability.

Generating and Applying a YAML File

First, generate the YAML definition using a dry run:

kubectl run redis --image=redis123 --dry-run=client -o yaml > redis.yaml

The generated redis.yaml file looks like this:

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: redis
  name: redis
spec:
  containers:
  - image: redis123
    name: redis
  resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

Create the pod from the YAML file:

kubectl create -f redis.yaml

Check the pod status:

kubectl get pods

Expected output is similar to:

NAME             READY   STATUS         RESTARTS   AGE
newpods-pnnx8    1/1     Running        0          8m16s
newpods-llstt    1/1     Running        0          8m16s
newpods-k87fx    1/1     Running        0          8m16s
nginx            1/1     Running        0          8m22s
redis            0/1     ErrImagePull   0          10s

Because the image name is incorrect, the redis pod is in an ErrImagePull state.

Updating the YAML to Correct the Image

To fix this error, edit the redis.yaml file to use the correct image name. Replace redis123 with redis:

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: redis
  name: redis
spec:
  containers:
  - image: redis
    name: redis
  resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

Apply the updated configuration:

kubectl apply -f redis.yaml

You might see a warning regarding a missing annotation, which is normal when applying changes to imperatively created resources.

Finally, verify that the pod is running:

kubectl get pods

An expected output would be:

NAME             READY   STATUS    RESTARTS   AGE
newpods-pnnx8    1/1     Running   0          9m38s
newpods-llstt    1/1     Running   0          9m38s
newpods-k87fx    1/1     Running   0          9m38s
nginx            1/1     Running   0          9m38s
redis            1/1     Running   0          92s

This confirms that the corrected pod is now in a running state.

Conclusion

In this lab, you learned how to:

• Verify the current pod count.
• Create new pods using different images.
• Inspect detailed pod configurations with kubectl describe.
• Understand the significance of the READY column.
• Delete faulty pods.
• Define and modify pod configurations using YAML.

These practical exercises provide a solid foundation for working with pods in Kubernetes. Happy learning and explore further to master Kubernetes operations!