Hands-on Lab·Certified Kubernetes Administrator
What Kubernetes Is and What It Does
Kubernetes is a database of desired state with programs that keep reality matching it. That one sentence explains almost every behaviour, including the ones that surprise people, and every claim in it can be shown with a command.
Foundations Guide 1 of 103 Beginner
- Kubernetes1.36.4
- Cluster1 node
- Runtimecontainerd 2.2.6
- CNICalico v3.32.1
- TimeAbout 30 min
Nothing here is version-specific. The resource and group counts vary with what is installed on a cluster.
| Server Name | IP Address | OS | Roles | CPU | RAM | HDD |
|---|---|---|---|---|---|---|
| CKA4001 | 192.168.0.191 | Ubuntu 26.04 LTS | Control Plane Node, Worker Node | 2 Core | 4 GB | 50 GB |
This guide includes
Use this when you have to explain what Kubernetes actually does, or when something you deleted keeps coming back. This matters because Kubernetes is a database of desired state with controllers that keep reality matching it, and almost every surprising behaviour follows from that one sentence.
- reading the API version and counting the resource kinds a cluster serves
- seeing every object as two halves -
specas the wish,statusas the report - applying an identical file twice and getting
unchanged, which is what declarative means - deleting a Pod, watching a controller replace it, and following the Deployment to ReplicaSet to Pod chain
- shipping a tag that does not exist, and finding the loop relentless but not intelligent
Before you start
- A cluster you can reach with
kubectl. Any cluster, including a single-node one. - Familiarity with containers, though not with Kubernetes.
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It is an API before it is anything else
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Every object is a wish and a report
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Declarative means the same file twice is a no-op
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Delete a Pod and watch a controller put it back
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The ownership chain, and why it is deterministic
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Level-triggered, not event-driven
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What it will not do for you