Components

In this lesson we cover Kustomize components — a way to package optional, reusable configuration so you can enable features selectively across overlays. A component is a self-contained bundle of Kubernetes resources, generators, and patches that represent an optional feature. Use components when a feature should be applied to some overlays but not others. If a feature must be present in every overlay, keep it in the base instead.

Components are reusable collections of Kubernetes resources, patches, secrets, and other Kustomize configuration related to a specific optional feature. They help you avoid copying the same configs across multiple overlays.

Visual example

Suppose our application has three overlays:

dev
premium
standalone (self-hosted)

A shared base configuration is used by all overlays. We also have two optional features:

caching (requires Redis) — enable only for premium and standalone
external database (Postgres) — enable only for dev and premium

Because each feature applies to a subset of overlays, components are a good fit: place the resources and patches for each feature into its own component folder, then import the appropriate component(s) into the overlays that need them.

Project layout

Example repository structure used in this lesson:

k8s/
├─ base/
│  ├─ kustomization.yaml
│  └─ api-depl.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

Implementing a component

Each component folder contains the resources needed for the feature and a kustomization.yaml whose kind is Component. The apiVersion should match the version of Kustomize you are using — many recent releases use kustomize.config.k8s.io/v1beta1. Example: Postgres deployment for the db component

# components/db/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

Component kustomization

A component kustomization.yaml must set kind: Component and list any resources, generators, and patches that implement the feature. In this example, the db component:

declares the Postgres Deployment as a resource,
generates a Secret for the DB password, and
provides a patch to modify the base api deployment to read that secret.

# components/db/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Component

resources:
  - postgres-depl.yaml

secretGenerator:
  - name: postgres-cred
    literals:
      - password=postgres123

patches:
  - deployment-patch.yaml

Ensure the apiVersion and kind: Component are compatible with your Kustomize version. Component support and fields may vary between releases — test locally with kustomize build for the overlay that imports the component.

Patch the base deployment

If a component must modify resources defined in the base, include patches in the component that target those base resources. For example, the base api deployment needs an environment variable to read the DB password from the generated secret:

# components/db/deployment-patch.yaml
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

Including a component in an overlay

To enable a feature for a particular overlay, import the component in that overlay’s kustomization.yaml under the components section. The overlay should still import the base via resources as usual. Example: the dev overlay needs the external database component:

# overlays/dev/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
  - ../../base

components:
  - ../../components/db

The premium overlay would include both ../../components/db and ../../components/caching if it requires both features.
The standalone overlay would include only ../../components/caching in this example.

Overlay to components matrix

Overlay	Components included
dev	`../../components/db`
premium	`../../components/db`, `../../components/caching`
standalone	`../../components/caching`

Summary

Components are reusable bundles of Kustomize resources, generators, and patches representing optional features.
Use components to enable features in some overlays but not others, keeping each feature’s code in a single place.
Overlays import the base and then list the components they require under components:.

Introduction

Core Concepts

Scheduling

Logging & Monitoring

Application Lifecycle Management

Cluster Maintenance

Security

Storage

Networking

Design and Install a Kubernetes Cluster

Install "Kubernetes the kubeadm way"

Troubleshooting

Helm Basics (2025 Updates)

Kustomize Basics (2025 Updates)

Other Topics

Mock Exams

Visual example

Project layout

Implementing a component

Component kustomization

Patch the base deployment

Including a component in an overlay

Overlay to components matrix

Summary

Links and references

Watch Video

Practice Lab

​Visual example

​Project layout

​Implementing a component

​Component kustomization

​Patch the base deployment

​Including a component in an overlay

​Overlay to components matrix

​Summary

​Links and references

Watch Video

Practice Lab

Visual example

Project layout

Implementing a component

Component kustomization

Patch the base deployment

Including a component in an overlay

Overlay to components matrix

Summary

Links and references