Kubernetes cheat sheet

1. 1How a cluster worksThe control plane decides, the nodes run. Every Kubernetes behaviour comes from controllers comparing what you asked for with what exists.7 concepts

   1. 1Desired state and reconciliationYou declare objects (a Deployment with three replicas) and controllers loop forever, comparing the declared spec with the observed status and acting to close…
   2. 2API serverThe front door of the cluster. kubectl, controllers, kubelets and CI all read and write objects through its REST API, which authenticates, authorises and…
   3. 3etcdA consistent, distributed key-value store holding every object in the cluster.
   4. 4Scheduler and controller managerThe scheduler assigns each new Pod to a node that fits its resource requests and constraints.
   5. 5kubeletThe agent on every node.
   6. 6Container runtime, kube-proxy and CNIThe runtime (usually containerd, through the CRI) runs containers.
   7. 7Managed clustersCloud services run and upgrade the control plane for you; you manage node pools (or let the provider manage them too) and your workloads. kind, k3d and minikube…

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2. 2kubectl essentialsThe command line you use to read, change and inspect everything in the cluster.7 concepts

   1. 1kubeconfig and contextskubeconfig (~/.kube/config or $KUBECONFIG) lists clusters, users and contexts.
   2. 2get and describekubectl get lists objects in a table, or full YAML with -o yaml.
   3. 3apply, diff and dry runskubectl apply -f creates or updates objects to match files.
   4. 4Labels and selectorsLabels are key and value pairs on objects, like app: api.
   5. 5Output formats and jsonpath-o yaml and -o json print full objects, -o wide adds columns, and -o jsonpath or custom-columns extract exactly the fields you want.
   6. 6kubectl explainPrints the schema and documentation for any field of any resource, straight from the cluster's API.
   7. 7Manifest anatomyEvery object has apiVersion, kind, metadata (name, namespace, labels, annotations) and usually spec (what you want).

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3. Pods and workload controllersThe Pod is the unit that runs. Controllers create and replace Pods for you, each suited to a different kind of work.7 conceptsOpens with credits
4. Probes, rollouts and rollbacksHow Kubernetes knows a Pod is healthy, and how it swaps versions without dropping traffic.8 conceptsOpens with credits
5. Services, Ingress and Gateway APIGiving changing Pods a stable address, and letting traffic in from outside the cluster.7 conceptsOpens with credits
6. Configuration, resources and scalingFeeding settings and secrets to Pods, sizing them honestly, and letting the cluster add or remove capacity.8 conceptsOpens with credits
7. Storage and stateful appsHow Pods get disks that outlive them, and how StatefulSets give databases stable identities.7 conceptsOpens with credits
8. Namespaces, RBAC and Pod securityDividing a cluster between teams and apps, and giving each person and workload only the access it needs.7 conceptsOpens with credits
9. Packaging with HelmHelm packages Kubernetes manifests as versioned, configurable charts and tracks every install as a release.8 conceptsOpens with credits
10. Debugging workloadsReading Pod states, events and logs, and getting a shell or a network view where you need one.7 conceptsOpens with credits
11. 11Glossary, A to ZEvery concept in the sheet and the smaller terms it uses, in one list.99 terms

Clusters, kubectl, workloads, Services, Gateway API, config, probes, scaling, storage, RBAC, Helm and debugging.