World K4: Notes, Lockers & Packages

Kustomize bases and overlays

You will learn: to run one app in two kitchens with a base and overlays, using kubectl apply -k.

Checked with Kubernetes 1.37 on 31 Oct 2026

The problem

You are here: cluster kind-dev namespace default

~/shop $ lsbase  overlays~/shop $ ls overlaysdev  prod~/shop $ ls overlays/prodkustomization.yaml  namespace.yaml  settings-patch.yaml

Same shop, two kitchens. Dev wants 1 tray and chatty logs. Prod wants 3 trays and quiet logs. Copy all the YAML twice? Then you fix every bug twice.

Watch

This is overlays/prod/kustomization.yaml. Tap the three lines that make prod different.

0 of 3 found

keeps one base recipe. Each is a sticky note on top, for one kitchen. The base never changes.

Try it

Preview prod first. This only prints YAML. Nothing reaches the cluster.

You are here: cluster kind-dev namespace default

dev-control-planeOpenManager

No trays here.

dev-workerOpen

No trays here.

dev-worker2Open

No trays here.

Time: +0s (sped up)

Hint

kubectl kustomize <folder> builds the overlay and prints it.

Predict

You just ran kubectl kustomize overlays/prod. How many prod trays are running now?

Try it

Now open the prod kitchen for real.

You are here: cluster kind-dev namespace default

dev-control-planeOpenManager

No trays here.

dev-workerOpen

No trays here.

dev-worker2Open

No trays here.

Time: +0s (sped up)

Hint

-k means: build this folder with Kustomize, then apply it.

Check

You are here: cluster kind-dev namespace default

~/shop $ kubectl apply -k overlays/devnamespace/dev createdconfigmap/settings createddeployment.apps/shop created~/shop $ kubectl apply -k overlays/prodnamespace/prod createdconfigmap/settings createddeployment.apps/shop created~/shop $ kubectl rollout status deployment/shop -n prod --timeout=120sWaiting for deployment "shop" rollout to finish: 0 of 3 updated replicas are available...deployment "shop" successfully rolled out~/shop $ kubectl exec -n dev deploy/shop -- printenv LOG_LEVELdebug~/shop $ kubectl exec -n prod deploy/shop -- printenv LOG_LEVELwarn

One base, two kitchens. Dev says debug, prod says warn. The patch changed one line of the note.

Check

Build the command that opens the dev kitchen.

Tap the pieces in the right order.

…

You did it!

You can now run one app in many kitchens with Kustomize.

Go deeper (optional)

Overlays can do more: images: swaps a tag, namePrefix: renames things, labels: adds labels. configMapGenerator adds a hash to the note’s name, so a change rolls the trays. kubectl diff -k overlays/prod shows changes first.

Real rep (optional), on a practice kind cluster:

Real mission

In the practice terminal above, cat each file under base and overlays. Make the same folders on your machine.
Preview prod.
kubectl kustomize overlays/prod
Open prod.
kubectl apply -k overlays/prod
Change count to 2 in the prod overlay. See the change before applying it.
kubectl diff -k overlays/prod
Close it. This deletes the prod zone.
kubectl delete -k overlays/prod

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