Pods — The Atomic Unit

The smallest deployable unit in Kubernetes.

beginner60 minRead → Lab → Quiz → Practice

🧠 Brain Warm-Up

🧠 Brain Warm-Up: If a Pod contains multiple containers (e.g. an API server and a logging agent), how do they communicate with each other? Can they listen on the same port? Think about their network boundaries before reading.

What is a Pod?

A Pod is the smallest deployable unit in Kubernetes. It wraps one or more containers that share the same network namespace, IP address, and storage volumes.

Key facts:

Every Pod gets one IP address — all containers inside share it.
Containers in the same Pod communicate via localhost on different ports. They cannot bind to the same port.
Pods are ephemeral — when they die, their filesystem is gone.
In practice, you almost never create bare Pods — you use Deployments instead.

Pod vs Container

Feature	Docker Container	Kubernetes Pod
Network	Its own IP	Shared with all co-located containers
Lifecycle	Individual	All containers start/stop together
Management	Manual	Orchestrated by Kubernetes

Pod Architecture (Shared Network & Storage)

┌─────────────────────────────────────────────────────────┐
│                       POD                               │
│  IP Address: 10.244.1.5 (Shared Network Namespace)      │
│                                                         │
│  ┌───────────────────────┐   ┌───────────────────────┐  │
│  │  Primary Container    │   │   Sidecar Container   │  │
│  │  (e.g., Node.js API)  │   │  (e.g., Logging Agent)│  │
│  │  Port: 8080           │   │  Port: 9000           │  │
│  └──────────┬────────────┘   └───────────┬───────────┘  │
│             │ (Communicate via localhost)│              │
│             └─────────────►◄─────────────┘              │
│             │                            │              │
│  ┌──────────▼────────────┐   ┌───────────▼───────────┐  │
│  │      Volume Mount     │   │      Volume Mount     │  │
│  └──────────┬────────────┘   └───────────┬───────────┘  │
│             │                            │              │
│             └─────────────►◄─────────────┘              │
│                           │                             │
│                  ┌────────▼────────┐                    │
│                  │  emptyDir Vol   │                    │
│                  └─────────────────┘                    │
└─────────────────────────────────────────────────────────┘

Pod Lifecycle

Pending → Running → Succeeded
                ↓
             Failed → (restart policy)

Pending — scheduled but waiting for image pull or resources.
Running — at least one container is running.
Succeeded — all containers exited with code 0.
Failed — at least one container exited non-zero.

←

kubectl & kubeconfig

Deployments — Managing Pod Lifecycle

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