Recap Demo Creating Pods with YAML

Welcome to this comprehensive guide on creating a Kubernetes pod using a YAML definition file. In this article, you will learn how to write a YAML file from scratch and deploy it into a Kubernetes cluster. You can create YAML files using any text editor, such as Notepad, Notepad++, or Atom, or even an integrated development environment (IDE) like PyCharm. I recommend PyCharm for its excellent YAML support. If you're interested, visit PyCharm by JetBrains to download the Professional or free Community edition.

Below is a step-by-step walkthrough to guide you in creating a pod definition file and deploying it on your Kubernetes environment.

Creating the Pod Definition File

1. Create a New Project and File

Begin by creating a new project called pod. Inside this project, create a file named pod-definition.yaml. Every Kubernetes YAML file typically includes the following root-level properties: apiVersion, kind, metadata, and spec. For a pod, set the apiVersion to v1 and kind to Pod.

2. Define the Metadata

In the metadata section, provide essential details such as the pod's name and associated labels for grouping. For instance:

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:

When using PyCharm, you'll notice a tree-view panel that displays the YAML file structure. This visualization confirms that apiVersion, kind, metadata, and spec are at the same root level. Make sure the name and labels entries have identical indentation. Incorrect indentation might mistakenly nest labels under name, leading to errors.

3. Adding Optional Labels

Enhance your pod's metadata by adding extra labels, such as cost center or geographical location, to better organize your resources. Here’s an example:

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
    costcenter: amer
    location: NA
spec:

This flexible labeling approach enables more efficient management of your deployments.

4. Define the Pod Spec

Under the spec section, specify the container details. The containers field accepts an array; each container is introduced by a dash (-) followed by its configuration, such as name and image. The example below defines a pod with a single container running an Nginx image:

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
    - name: nginx-container
      image: nginx

For scenarios with multiple containers, add another item to the list. For example:

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
    - name: nginx-container
      image: nginx
    - name: backend-container
      image: redis

Deploying the Pod

After finalizing your pod-definition.yaml, follow these instructions to deploy it to your Kubernetes cluster.

1. Setup Folder Structure on the Kubernetes Master Node

Log in to your Kubernetes master node and create a directory structure for your demos:

root@kubemaster:/home/osboxes# mkdir demos
root@kubemaster:/home/osboxes# cd demos
root@kubemaster:/home/osboxes/demos# mkdir pod
root@kubemaster:/home/osboxes/demos# cd pod

2. Create the YAML File

Paste the contents of your pod-definition.yaml into a new file on the master node. For instance, execute:

root@kubemaster:/home/osboxes/demos/pod# cat > pod-definition.yml
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
    - name: nginx-container
      image: nginx

After creating the file, verify its contents using the cat command.

3. Clean Up Existing Pods

Before deploying your new pod, ensure there are no conflicting pods already running. If a pod was previously deployed with a command like kubectl run, delete it by executing:

root@kubemaster:/home/osboxes/demos/pod# kubectl get pods
NAME                           READY   STATUS    RESTARTS   AGE
nginx-8586cf59-wf5r4           1/1     Running   0          59m
root@kubemaster:/home/osboxes/demos/pod# kubectl delete deployment nginx

Confirm the deletion by listing pods again:

root@kubemaster:/home/osboxes/demos/pod# kubectl get pods
No resources found.

4. Create the Pod

Now, create the pod with the following command:

root@kubemaster:/home/osboxes/demos/pod# kubectl create -f pod-definition.yml
pod "myapp-pod" created

You can monitor the pod’s creation by running:

root@kubemaster:/home/osboxes/demos/pod# kubectl get pods
NAME        READY   STATUS             RESTARTS   AGE
myapp-pod   0/1     ContainerCreating   0          8s

After a few moments, check the pod status again:

root@kubemaster:/home/osboxes/demos/pod# kubectl get pods
NAME        READY   STATUS      RESTARTS   AGE
myapp-pod   1/1     Running     0          19s

This confirms the pod has been successfully created and is now running in your cluster.

That concludes our guide on creating a Kubernetes pod using a YAML file. In the next article, we’ll explore additional tips for managing YAML files in PyCharm. Happy coding and deployment!

Additional Resources

• Kubernetes Documentation
• Kubernetes Basics
• Docker Hub
• Terraform Registry