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In this guide, you’ll learn how to define and consume components in Kustomize. Components let you package optional features—such as additional resources, patches, ConfigMaps, or Secrets—into self-contained units. You can then import them in selected overlays without duplicating code, ensuring consistency and reducing configuration drift.

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When to Use Components

Use components when an application offers optional features that only apply to some overlays. If a feature is required in all overlays, include it in your base. For features needed by only a subset, bundle them as components to avoid repetition.

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Visual Example

Consider three deployment environments:
  • dev (development)
  • premium (for premium customers)
  • standalone (self-hosted)
Our shared base/ folder holds common resources. We also have two optional features:
  • Caching (backed by Redis) — enabled in premium and standalone
  • External DB (Postgres) — enabled in dev and premium
Where should we place the Redis and Postgres manifests so only the right overlays include them?
The image is a flowchart showing components with connections between "base," "caching," "dev," "Premium," and "Self hosted." It also lists "Caching" and "External DB" with related items.
Instead of duplicating manifests in overlays—or adding unwanted features to base—we create two components (caching and db) and import them selectively.
The image is a flowchart titled "Components" showing a hierarchy with nodes labeled "base," "dev," "Premium," "Self hosted," "Components," "caching," and "db." It illustrates the relationships between these components.

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Component Features Table

ComponentPurposeOverlays
cachingRedis Deployment & servicepremium, standalone
db (External)Postgres Deployment & DB secretsdev, premium

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Project Structure

k8s/
├── base/
│   ├── api-depl.yaml
│   └── kustomization.yaml
├── components/
│   ├── caching/
│   │   ├── kustomization.yaml
│   │   ├── deployment-patch.yaml
│   │   └── redis-depl.yaml
│   └── db/
│       ├── kustomization.yaml
│       ├── deployment-patch.yaml
│       └── postgres-depl.yaml
└── overlays/
    ├── dev/
    │   └── kustomization.yaml
    ├── premium/
    │   └── kustomization.yaml
    └── standalone/
        └── kustomization.yaml
  • base/: Common resources (e.g., API Deployment)
  • components/: Feature directories (caching/, db/)
  • overlays/: Environment-specific kustomizations

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Database Component

The db component adds a Postgres deployment, a Secret for credentials, and patches your API Deployment.

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postgres-depl.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: postgres-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      component: postgres
  template:
    metadata:
      labels:
        component: postgres
    spec:
      containers:
        - name: postgres
          image: postgres:latest
Components require kind: Component with the v1alpha1 API. Ensure you’re running Kustomize v4.x or later.

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kustomization.yaml (Component)

apiVersion: kustomize.config.k8s.io/v1alpha1
kind: Component
resources:
  - postgres-depl.yaml
secretGenerator:
  - name: postgres-cred
    literals:
      - password=postgres123
patches:
  - deployment-patch.yaml

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deployment-patch.yaml

This strategic merge patch injects the DB_PASSWORD from the Secret into your API Deployment: 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: api-deployment
spec:
  template:
    spec:
      containers:
        - name: api
          env:
            - name: DB_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: postgres-cred
                  key: password

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Overlay Configuration

Each overlay’s kustomization.yaml pulls in base plus the desired components.

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Example: Dev Overlay

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - ../../base
components:
  - ../../components/db
  • premium overlay adds both ../../components/db and ../../components/caching.
  • standalone overlay adds only ../../components/caching.
With Kustomize components, you can define optional feature logic once and enable it in any overlay by adding a single entry.

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