Pods

Pods — The Building Blocks

A Pod is the smallest deployable unit in Kubernetes. It is a wrapper around one or more containers that share storage, network, and a specification for how to run.

In most cases, you will run one container per Pod. But multi-container Pods are useful when containers need to share resources closely — like a web server and a sidecar logging agent.

Pod Lifecycle

  Pod States:
  ┌──────────┐    ┌──────────┐    ┌──────────┐    ┌──────────┐
  │ Pending  │───▶│ Running  │───▶│Succeeded │    │  Failed  │
  │ (waiting)│    │ (active) │    │ (completed)  │ (crashed) │
  └──────────┘    └──────────┘    └──────────┘    └──────────┘
                                      │                │
                                      └────────┬───────┘
                                               ▼
                                         Unknown
                                       (status unclear)

Pending — Pod has been accepted but containers are not yet running. It might be waiting for scheduling or pulling images.

Running — At least one container is still running.

Succeeded — All containers terminated successfully (exit code 0).

Failed — At least one container terminated with a non-zero exit code.

Writing a Pod Manifest

apiVersion: v1
kind: Pod
metadata:
  name: my-first-pod
  labels:
    app: hello
spec:
  containers:
    - name: nginx
      image: nginx:1.25
      ports:
        - containerPort: 80
      resources:
        requests:
          memory: "64Mi"
          cpu: "250m"
        limits:
          memory: "128Mi"
          cpu: "500m"

labels — Key-value pairs used to organize and select resources. You will use labels extensively in Kubernetes.

resources — Always set resource requests and limits. Requests help the scheduler place the pod; limits prevent a container from consuming too much.

Working with Pods

# Create a pod
kubectl apply -f pod.yaml

# List pods
kubectl get pods

# Describe a pod (see events and details)
kubectl describe pod my-first-pod

# View logs
kubectl logs my-first-pod

# Execute a command inside the pod
kubectl exec -it my-first-pod -- /bin/bash

# Delete a pod
kubectl delete pod my-first-pod

Why You Rarely Create Pods Directly

Pods are ephemeral. When a pod dies, it is gone forever. Instead of creating pods directly, you use Deployments and ReplicaSets to manage pod lifecycle automatically. We will cover that in the Workloads section.