Pod

What is Pod?

Pod is a single instance of an application and is the smallest unit of a Kubernetes application. It basically wraps container or provides an abstraction layer over container. Normally, pod is only run one application container inside it (one-to-one relationship).

Each pod will get its IP address and when the pod is recreated, then the new IP address will be assigned to that pod. So, the pod can use its IP address to communicate with each other pods using its internal IP address.

Multi-container pods

Multi-container pods are like helper containers. The two or more containers can communicate directly via localhost as they share the same network space. Of course, they are sharing the same storage space as well.

Commands

# Deploy nginx image to pod with the pod-name "nginx"
kubectl run <pod-name> --image=<image>
 
# Example
kubectl run nginx --image=nginx
kubectl run nginx --image=nginx --port=8000 # container exposes port
kubectl run nginx --image=nginx --port=8080 --expose # Create a cluster IP associated with the pod port number
 
kubectl get pods
kubectl get pod <pod-name>
kubectl describe pod <pod-name>
kubectl delete pod <pod-name>
 
kubectl exec <pod-name> -- <command>
kubectl exec mypod -- /bin/bash
 
kubectl apply -f <filename>
kubectl create -f <filename>
 
kubectl edit pod <pod-name>
 
# extract pod definition to a file
kubectl get pod <pod-name> -o yaml > pod.yaml

Pod YAML File

Here is the sample pod YAML file, to apply this file, you need to type kubectl apply -f pod.yaml.

apiVersion: v1
kind: Pod
metadata:
  name: myapp
  labels:
    name: myapp
spec:
  containers:
    - name: myapp
      image: nginx
      ports:
        - containerPort: 8080