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Topic 2: Container Runtime And CRI

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Topic 2: Container Runtime And CRI

Official baseline: (The Kubernetes Authors, 2026a, 2026b). My working version: kubelet does not run containers directly. It talks through the Container Runtime Interface to a runtime such as containerd.

Mental Model

kubelet does not run containers directly. It talks through the Container Runtime Interface to a runtime such as containerd.

Notes

  • Runtime health becomes node health.
  • Runtime logs and kubelet logs usually explain image pull and sandbox failures.
  • Different runtimes can mean different isolation and performance tradeoffs.

Homelab Angle

Keep the runtime boring unless you are intentionally learning isolation, GPU, or edge constraints.

Verify It

  • Read the object status before changing the manifest.
  • Check events for the controller or node that is actually complaining.
  • Confirm the official source linked below still matches the cluster version you run.

Common Failure Modes

  • Treating the YAML object as the system, instead of one input to a reconciliation loop.
  • Debugging from outside the cluster when the failure only exists inside cluster networking or node state.
  • Forgetting that Kubernetes version, addon version, and runtime behavior are linked.

Sources

  • Container Runtimes - source path: content/en/docs/setup/production-environment/container-runtimes.md, commit 8cc9e19b8eec8d5cf49eacd66f86a81648edb1a0.
  • Containers - source path: content/en/docs/concepts/containers/_index.md, commit 8cc9e19b8eec8d5cf49eacd66f86a81648edb1a0.
  • Kubernetes documentation is licensed under CC BY 4.0; these notes are original commentary and link back to the official source.
The Kubernetes Authors. (2026a). Container Runtimes. https://kubernetes.io/docs/setup/production-environment/container-runtimes/
The Kubernetes Authors. (2026b). Containers. https://kubernetes.io/docs/concepts/containers/

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