kubectl kustomize: Command Reference for CI/CD

Render a kustomize overlay to plain YAML for review or apply.

kubectl kustomize builds a kustomize directory and prints the rendered manifests to stdout, without touching the cluster. It is the render half; apply -k is render-and-apply. This reference covers both and a per-environment CI flow.

Common flags and usage

• kustomize <dir>: render an overlay to stdout (no cluster access)
• apply -k <dir>: render and apply in one step
• --enable-helm: allow the helmCharts kustomize feature
• Pipe rendered output into apply, diff, or a policy check
• Overlays under overlays/<env> layer onto a shared base

Example

# Render, preview the diff, then apply the prod overlay
kubectl kustomize overlays/prod > /tmp/rendered.yaml
kubectl diff -f /tmp/rendered.yaml || true
kubectl apply -f /tmp/rendered.yaml --server-side

In CI

Rendering to stdout first lets you run policy or lint checks on the exact YAML before it reaches the cluster, and feed it to kubectl diff for a review-friendly preview. apply -k is the shorthand when you do not need the intermediate artifact.

Key takeaways

• kustomize renders to stdout; apply -k renders and applies.
• Rendering first lets you lint, diff, and policy-check the exact YAML.
• Per-environment overlays layer onto one shared base.

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