Steps to create your First POD in Google Kubernetes

In this blog, we will show you the steps to create your first POD in Google Kubernetes Environment.

REQUIREMENTS

• 2 Node Cluster ( 1 Master VM with 2 Nodes)
• Kubernetes Components

INFRASTRUCTURE OVERVIEW

• We have already installed and configured the 2 Node cluster in our demo environment.
• Please check the URL https://blog.assistanz.com/steps-to-install-kubernetes-cluster-manually-using-centos-7/ for more information.

WORKING WITH PODS

• The smallest unit of scheduling in the kubernetes world is POD.
• POD’s can contain one or more containers.
• We deploy a POD in a cluster using the manifest file.
• We provide the manifest file to the API server. It will schedule to deploy in a node. Based on the manifest file, the POD will have one (or) more containers.
• irrespective how many containers inside a POD, the POD will get only a single IP. It’s like one IP to one POD relationship.
• Every container inside a POD shares single Network Namespace.
• All the containers inside a POD shares same CGROUP Limits, Volumes, Network and IPC namespaces.

INTER-POD COMMUNICATION

• All the POD addresses are fully routable on the POD Network.
• Every POD gets own IP and it’s routable to that Network.
• POD’s can communicate each other without any port mapping.

INTRA-POD COMMUNICATION

• Inside the POD, the multiple containers will communicate through a shared local network interface.
• The containers will be available outside the POD by exposing them through ports.
• Two containers cannot use the same port.
• Pods will either run as fully functional (or) its down completely.

POD LIFECYCLE

• First, we will create a manifest file (YAML or JSON) about POD and container information.
• Provide the manifest file to the API server and it will get scheduled to a node.
• Once its schedule, it goes into Pending state. During this time it will be downloading the images and files.
• It will be in pending state till all the containers are up and running.
• After the containers are up and running, It changes to running state.
• Once it’s completed its job, its change the status to succeed.
• If it’s holding on pending state (or) Crashed for a long time, then it will be changed to a failed state.
• We cannot bring back the death POD. Need to replace them with a new one.

CREATING A MANIFEST FILE

• Log in to the Kubernetes master server through putty.

• Create a new manifest file using vi editor.

Note: We are using YAML type to create the manifest files

• We are using the ngnix image for this demo purpose. Add the below code in the YAML file.

apiVersion: v1
kind: Pod
metadata:
   name: hello-pod
   labels:
      zone: pod
      version: v1
spec:
   containers:
      - name: hello-ctr
        image: nginx:latest

• Save and close the file.

Note: Make sure that manifest will be on right YAML format. Or else, it will show the error during POD deployment.

DEPLOYING THE POD

• From the shell, use the below command to create a pod.

kubectl create -f pod.yml

• A new POD will be created in few seconds.

• We can get the pods status using the below command.

kubectl get pods

• You can also get the POD events information through describe command.

kubectl describe pods <pod name>

• You can find the POD IP using wide option.

kubectl get pods -o wide

• We can able to browse the container using the POD IP inside the cluster.

curl -v http://<Pod IP>

EXTERNAL LINKS

https://www.mirantis.com/blog/introduction-to-yaml-creating-a-kubernetes-deployment/ – YAML Introduction.

VIDEO

Thanks for reading this blog. We hope it was useful for you to learn about POD creation on Google Kubernetes Environment.