Kustomize Controller

The Kustomize Controller is the Flux component that ensures your cluster’s actual state matches the desired state described by Kubernetes manifests. It retrieves artifacts from the Source Controller and then:

Feature	Description
Validation	Checks your manifests against the Kubernetes API before applying changes.
Apply / Update	Creates or updates resources based on the desired state.
Health Assessment	Monitors workloads to ensure they remain healthy after deployment.
Pruning (Garbage Collection)	Optionally removes resources that no longer exist in your source manifests.

Make sure you have installed Flux and configured a GitRepository or other supported source.

1. Creating a Kustomization

Use the flux create kustomization command to link your source to a path containing Kustomize overlays. You can also enable garbage collection:

flux create kustomization kustomization-app1 \
  --source=GitRepository/source-app1 \
  --path=./solar-system \
  --prune=true \
  --export > kustomization.yaml

The --export flag prints the Kustomization resource manifest:

apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
kind: Kustomization
metadata:
  name: kustomization-app1
  namespace: flux-system
spec:
  interval: 1m0s
  path: ./solar-system
  prune: true
  sourceRef:
    kind: GitRepository
    name: source-app1

Apply it with:

kubectl apply -f kustomization.yaml

2. Automatic Build Behavior

If there’s no kustomization.yaml file under ./solar-system, Flux will auto-generate one for you:

kustomize create --autodetect --recursive --output kustomization.yaml

This populates kustomization.yaml with all discovered resources:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - deployment.yaml
  - service.yaml

You don’t need to run the above command yourself—Flux performs it automatically when needed.

3. Providing Your Own Overlays

If you include a custom kustomization.yaml (or Kustomization overlay) in the specified path, the controller will skip auto-generation and apply your overlays directly. This allows you to:

Add labels or annotations
Patch existing resources
Customize namespace or image tags

4. Checking Status

To inspect all active Kustomization resources and their reconciliation state:

flux get kustomizations

Example output:

NAME                   REVISION          SUSPENDED   READY   MESSAGE
flux-system            main/7e35674...   False       True    Applied revision: 'main/7e35674...'
kustomization-app1     main/1b31558...   False       True    Applied revision: 'main/1b31558...'

GitOps Overview

Flux Overview

Source and Kustomize Controller

Helm Controller and OCI Registry

Image Automation Controller

Secret Management & Sign Verification

Notification Controller

Monitoring & User Interface

Kustomize Controller

1. Creating a Kustomization

2. Automatic Build Behavior

3. Providing Your Own Overlays

4. Checking Status

Links and References

Watch Video

​1. Creating a Kustomization

​2. Automatic Build Behavior

​3. Providing Your Own Overlays

​4. Checking Status

​Links and References

Watch Video

1. Creating a Kustomization

2. Automatic Build Behavior

3. Providing Your Own Overlays

4. Checking Status

Links and References