Understanding Pods

The Pod is the most fundamental building block in Kubernetes. Every container you run, every application you deploy -- it all starts with a Pod.

What Is a Pod?

A Pod is the smallest deployable unit in Kubernetes. It represents a single instance of a running process in your cluster. A Pod wraps one or more containers and provides them with shared networking and storage.

Think of a Pod as an apartment. The containers inside are the roommates -- they share the same address (IP), the same front door (network namespace), and the same living space (storage volumes).

Single vs Multi-Container Pods

Single-container Pods are the most common pattern. One Pod, one container, one purpose.

Multi-container Pods are used when containers need to work closely together. Common multi-container patterns include:

• Sidecar -- a helper container that enhances the main container (like a logging agent)
• Init container -- runs before the main container to set things up (like running database migrations)
• Ambassador -- a proxy container that handles connections for the main container

In most cases, you will use single-container Pods.

Pod Lifecycle

A Pod moves through several phases during its lifetime:

# Check the phase of your pods
kubectl get pods

# Get detailed status information
kubectl describe pod my-app

Creating a Pod Imperatively

The imperative approach creates a Pod directly from the command line:

# Run an nginx pod
kubectl run my-nginx --image=nginx

# Run a pod and immediately open a shell
kubectl run debug-pod --image=busybox -it --rm -- /bin/sh

This is great for quick testing and debugging.

Creating a Pod Declaratively

The declarative approach uses a YAML manifest file. This is the recommended method for production workloads.

apiVersion: v1
kind: Pod
metadata:
  name: my-nginx
  labels:
    app: nginx
    environment: dev
spec:
  containers:
    - name: nginx
      image: nginx:1.27
      ports:
        - containerPort: 80
      resources:
        requests:
          memory: "64Mi"
          cpu: "250m"
        limits:
          memory: "128Mi"
          cpu: "500m"

Apply the manifest:

# Create the pod from the YAML file
kubectl apply -f pod.yaml

# Check that it is running
kubectl get pod my-nginx

# See detailed information
kubectl describe pod my-nginx

# View the pod logs
kubectl logs my-nginx

# Delete the pod when done
kubectl delete pod my-nginx

Key Takeaways

• A Pod is the smallest deployable unit, wrapping one or more containers
• Single-container Pods are the most common pattern
• Pods have a lifecycle: Pending, Running, Succeeded, Failed, Unknown
• Imperative creation (kubectl run) is fast for testing
• Declarative creation (kubectl apply -f) is best for reproducible, production workloads
• Always define resource requests and limits in your Pod specs