Kubelet in Kubernetes

The Kubelet is a Kubernetes component that runs on every worker node and is responsible for managing Pods and containers on that node.

It acts as the bridge between the Control Plane and the container runtime.

Main Responsibilities

• Registers the node with the Kubernetes cluster.
• Receives instructions to run Pods.
• Communicates with the container runtime to start/stop containers.
• Pulls required container images.
• Continuously monitors Pods and containers.
• Ensures containers remain healthy and running as expected.
• Reports node and Pod status to the Kube API Server.

Basic Flow

Kube Scheduler
      ↓
Kube API Server
      ↓
   Kubelet
      ↓
Container Runtime
      ↓
  Containers

The Kubelet does not decide which node a Pod runs on. That decision is made by the Kube Scheduler.

Kubelet and Container Runtime

When the Kubelet receives instructions to run a Pod, it communicates with the container runtime.

Kubelet
   ↓
Container Runtime
   ↓
Pull Image
   ↓
Start Container
   ↓
Monitor Container

Examples of container runtimes include containerd and CRI-O.

Installing Kubelet

Unlike some Control Plane components, the Kubelet must be installed on worker nodes.

A typical Kubelet configuration includes:

ExecStart=/usr/local/bin/kubelet \
  --config=/var/lib/kubelet/kubelet-config.yaml \
  --container-runtime-endpoint=unix:///var/run/containerd/containerd.sock \
  --kubeconfig=/var/lib/kubelet/kubeconfig \
  --register-node=true \
  --v=2

Configuration options can vary depending on the Kubernetes version and setup.

Verify Kubelet

Check whether the Kubelet process is running:

ps -aux | grep kubelet

We can also check the node from the Control Plane:

kubectl get nodes

Kubelet vs Scheduler

Component	Responsibility
Kube Scheduler	Decides which node should run a Pod
Kubelet	Runs and manages the Pod on that node
Container Runtime	Actually runs the containers
API Server	Coordinates communication

Key Takeaway

Kubelet = Node-level Pod manager.

The Kubelet runs on each worker node, manages Pods and containers through the container runtime, monitors their health, and reports their status to the Kubernetes API Server.