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How does Kustomize handle environment-specific configuration?

Infrastructure as Code (Terraform, Ansible) · Advanced level

Answer

Kustomize handles environment-specific configuration through overlays, patches, name prefixes or suffixes, namespaces, image overrides, common labels, and generators. Each environment can have a small overlay that transforms a shared base.

Technical explanation

Common patterns include overlays/dev, overlays/stage, and overlays/prod.

Image tags and replicas are frequent environment-specific differences.

Secrets should still be handled with a secure process; generated Secret YAML alone is not secret management.

Keep source manifests or IaC definitions readable enough that reviewers can understand the final desired state.

Use overlays, modules, or roles for reuse, but keep environment-specific differences explicit and reviewable.

Validate generated output in CI before applying it through kubectl, Argo CD, Terraform, or Ansible.

Hands-on example

1. Create a Kustomize base and overlay for: How does Kustomize handle environment-specific configuration?

2. Base files:

base/deployment.yaml

base/service.yaml

base/kustomization.yaml

base/kustomization.yaml:

resources:

- deployment.yaml

- service.yaml

commonLabels:

app.kubernetes.io/name: payments

3. prod overlay:

resources:

- ../../base

namePrefix: prod-

namespace: payments-prod

images:

- name: ghcr.io/company/payments

newTag: 1.8.4

configMapGenerator:

- name: app-config

literals:

- LOG_LEVEL=info

patches:

- path: replica-patch.yaml

4. Render and apply:

kubectl kustomize overlays/prod

kubectl diff -k overlays/prod

kubectl apply -k overlays/prod

5. In GitOps, point Argo CD at overlays/prod and let it render, compare, and sync the desired state.

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• What does terraform init do?
• What is the Terraform state file, and why is it critical?
• Why should state be stored remotely, and what backend would you use on AWS?
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