Worker nodes
Module infographic
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Revision poster: seven steps, seven narrow jobs.

Infographic: kubectl apply flows through the API server, etcd, controller manager and scheduler to the kubelet and containerd on a worker node
Click the poster to enlarge it

Trace the numbered arrows from kubectl on the left to the Pods on the right, then back with the status report.

  1. 11 kubectl submits the manifest; the API server authenticates, authorizes and admits it.
  2. 22 The desired state is stored in etcd by the API server.
  3. 33 The controller manager creates the Pods.
  4. 44 The scheduler picks a node for each Pod.
  5. 55 The kubelet on that node sees its Pod.
  6. 66 containerd starts the containers.
  7. 77 The kubelet reports status back to the API server.

Self-check: cover the poster and answer

  • Pods are created but stay Pending: which step has stalled?
  • Why can the scheduler never start a container itself?

Seven components each do one narrow job, and nothing but the API server touches etcd.

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