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1. What is Kustomize?¶

• A Kubernetes-native configuration management tool.
• Allows you to customize YAML manifests without templates.
• Works by layering configurations in a structured way.

2. Managing Directories (Base)¶

• Base contains common manifests (e.g., Deployments, Services).

• kustomization.yaml in the base defines:

• resources → Which manifests to include.

• transformers (optional) → Modify labels, annotations, etc.
• patches (optional) → Adjust specific fields.
• Purpose: Create a clean, reusable starting point for all environments.

3. Overlays (Environment-Specific Configs)¶

• Overlays extend or modify the base for each environment (dev, staging, prod).
• Each overlay has its own kustomization.yaml.

• Typical use cases:

• Change replica counts.

• Add or remove resources (e.g., Grafana only in prod).
• Apply patches for environment-specific changes.
• Command example:

kubectl apply -k overlays/dev
kubectl apply -k overlays/prod

4. Components (Optional, Reusable Features)¶

• Components solve the problem of optional add-ons.
• Defined using kind: Component.
• Examples: Monitoring (Grafana), Network Policies, Logging.
• Integrated into overlays when needed:

components:
  - ../../components/monitoring
  - ../../components/network-policy

5. Strategy & Flow¶

1. Base → Common configuration for all.
2. Overlays → Environment-specific adjustments.
3. Components → Optional features added on top.

This sequence ensures:

• Reusability (no duplication).
• Flexibility (easy per-environment differences).
• Scalability (clean management as apps grow).

6. Key Commands¶

# Validate output without applying
kustomize build overlays/prod

# Apply directly
kubectl apply -k overlays/prod

Final Takeaway¶

• Base = foundation (always used).
• Overlays = environment-specific changes.
• Components = optional reusable features.
• Together, they give a structured and scalable way to manage Kubernetes manifests.