Note_Tech

All technological notes.

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Kubernetes - `kubelet`

kubelet
- the agent that runs on every node in a Kubernetes cluster and ensures that containers are running in Pods as expected on its node.
Primary Roles
- Node Registration & Management
  - Registers the node with the cluster’s API Server.
  - Ensures node labels, capacity, and conditions are kept up to date.
- Static Pod Management
  - Runs Pods defined locally on the node (in /etc/kubernetes/manifests/).
  - Commonly used to run control plane components on master nodes.
- Pod Lifecycle Management
  - Watches the API Server for Pods assigned to its node.
  - Creates, starts, stops, and deletes containers to match the PodSpec.
  - Continuously checks and reconciles: “Are the right Pods running on this node?”
- Interface to Container Runtime
  - Talks to the container runtime (Docker, containerd, CRI-O) via the Container Runtime Interface (CRI).
  - Actually launches containers as requested in PodSpecs.
- Health Monitoring & Reporting
  - Runs liveness, readiness, and startup probes for containers.
  - Reports Pod and Node status (e.g., CPU/memory pressure, health) back to the API Server.