Chapter One
Foundations
The mental model behind Kubernetes — declarative desired state and the reconcile loop — plus what a container really is and how a cluster is assembled.
Kubernetes has a reputation for being hard. Part of that is real — it is a large system with many moving parts. Most of it is that the parts are taught before the one idea that ties them together: declarative desired state reconciled by a control loop.
This chapter builds that foundation. What a container actually is and the runtime beneath it, how a cluster splits into a control plane and worker nodes, and how every command you run is just a request to one API server. Everything later assumes these four pages.
Topics in This Chapter
Topic 01
What Kubernetes Is
The container orchestrator that won, and the declarative model at its core. You describe the end state; the reconcile loop makes it true and keeps it true.
Topic 02
Containers and Runtimes
What an image and a container really are, and the runtime chain from kubelet through the CRI to containerd and runc. Why Dockershim was removed.
Topic 03
Cluster Architecture
The control plane — API server, etcd, scheduler, controllers — and the worker nodes that run kubelet and a container runtime. Who decides and who does the work.
Topic 04
kubectl and the API
Every action is a REST call to the API server. How kubectl, manifests, and apply work, and why the single front door makes the system consistent everywhere.