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Frequently asked questions

Flux and the GitOps Toolkit frequently asked questions.

General questions

Does Flux have a UI / GUI?

The Flux project does not provide a UI of its own, but there are a variety of UIs for Flux in the Flux Ecosystem.

Weave GitOps

VS Code GitOps Tools

Where can I find information about Flux release cadence and supported versions?

Flux is at least released at the same rate as Kubernetes, following their cadence of three minor releases per year.

For Flux the CLI and its controllers, we support the last three minor releases. Critical bug fixes, such as security fixes, may be back-ported to those three minor versions as patch releases, depending on severity and feasibility.

For more details please see the Flux release documentation.

Kustomize questions

Are there two Kustomization types?

Yes, the kustomization.kustomize.toolkit.fluxcd.io is a Kubernetes custom resource while kustomization.kustomize.config.k8s.io is the type used to configure a Kustomize overlay.

The kustomization.kustomize.toolkit.fluxcd.io object refers to a kustomization.yaml file path inside a Git repository or Bucket source.

How do I use them together?

Assuming an app repository with ./deploy/prod/kustomization.yaml:

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

Define a source of type gitrepository.source.toolkit.fluxcd.io that pulls changes from the app repository every 5 minutes inside the cluster:

apiVersion: source.toolkit.fluxcd.io/v1
kind: GitRepository
metadata:
  name: my-app
  namespace: default
spec:
  interval: 5m
  url: https://github.com/my-org/my-app
  ref:
    branch: main

Then define a kustomization.kustomize.toolkit.fluxcd.io that uses the kustomization.yaml from ./deploy/prod to determine which resources to create, update or delete:

apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: my-app
  namespace: default
spec:
  interval: 15m
  path: "./deploy/prod"
  prune: true
  sourceRef:
    kind: GitRepository
    name: my-app

What is a Kustomization reconciliation?

In the above example, we pull changes from Git every 5 minutes, and a new commit will trigger a reconciliation of all the Kustomization objects using that source.

Depending on your configuration, a reconciliation can mean:

generating a kustomization.yaml file in the specified path
building the kustomize overlay
decrypting secrets
validating the manifests with client or server-side dry-run
applying changes on the cluster
health checking of deployed workloads
garbage collection of resources removed from Git
issuing events about the reconciliation result
recoding metrics about the reconciliation process

The 15 minutes reconciliation interval, is the interval at which you want to undo manual changes .e.g. kubectl set image deployment/my-app by reapplying the latest commit on the cluster.

Note that a reconciliation will override all fields of a Kubernetes object, that diverge from Git. For example, you’ll have to omit the spec.replicas field from your Deployments YAMLs if you are using a HorizontalPodAutoscaler that changes the replicas in-cluster.

Can I use repositories with plain YAMLs?

Yes, you can specify the path where the Kubernetes manifests are, and kustomize-controller will generate a kustomization.yaml if one doesn’t exist.

Assuming an app repository with the following structure:

├── deploy
│   └── prod
│       ├── .yamllint.yaml
│       ├── deployment.yaml
│       ├── service.yaml
│       └── ingress.yaml
└── src

Create a GitRepository definition and exclude all the files that are not Kubernetes manifests:

apiVersion: source.toolkit.fluxcd.io/v1
kind: GitRepository
metadata:
  name: my-app
  namespace: default
spec:
  interval: 5m
  url: https://github.com/my-org/my-app
  ref:
    branch: main
  ignore: |
    # exclude all
    /*
    # include deploy dir
    !/deploy
    # exclude non-Kubernetes YAMLs
    /deploy/**/.yamllint.yaml

Then create a Kustomization definition to reconcile the ./deploy/prod dir:

apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: my-app
  namespace: default
spec:
  interval: 15m
  path: "./deploy/prod"
  prune: true
  sourceRef:
    kind: GitRepository
    name: my-app

With the above configuration, source-controller will pull the Kubernetes manifests from the app repository and kustomize-controller will generate a kustomization.yaml including all the resources found with ./deploy/prod/**/*.yaml.

The kustomize-controller creates kustomization.yaml files similar to:

cd ./deploy/prod && kustomize create --autodetect --recursive

How can I safely move resources from one dir to another?

To move manifests from a directory synced by a Flux Kustomization to another dir synced by a different Kustomization, first you need to disable garbage collection then move the files.

Assuming you have two Flux Kustomization named app1 and app2, and you want to move a deployment manifests named deploy.yaml from app1 to app2:

Disable garbage collection by setting prune: false in the app1 Flux Kustomization. Commit, push and reconcile the changes e.g. flux reconcile ks flux-system --with-source.
Verify that pruning is disabled in-cluster with flux export ks app1.
Move the deploy.yaml manifest to the app2 dir, then commit, push and reconcile e.g. flux reconcile ks app2 --with-source.
Verify that the deployment is now managed by the app2 Kustomization with flux tree ks apps2.
Reconcile the app1 Kustomization and verify that the deployment is no longer managed by it flux reconcile ks app1 && flux tree ks app1.
Finally, enable garbage collection by setting prune: true in app1 Kustomization, then commit and push the changes upstream.

Another option is to disable the garbage collection of the objects using an annotation:

Disable garbage collection in the deploy.yaml by adding the kustomize.toolkit.fluxcd.io/prune: disabled annotation.
Commit, push and reconcile the changes e.g. flux reconcile ks flux-system --with-source.
Verify that the annotation has been applied kubectl get deploy/app1 -o yaml.
Move the deploy.yaml manifest to the app2 dir, then commit, push and reconcile e.g. flux reconcile ks app2 --with-source.
Reconcile the app1 Kustomization and verify that the deployment is no longer managed by it flux reconcile ks app1 && flux tree ks app1.
Finally, enable garbage collection by setting kustomize.toolkit.fluxcd.io/prune: enabled, then commit and push the changes upstream.

How can I safely rename a Flux Kustomization?

If a Flux Kustomization has spec.prune set to true and you rename the object, then all reconciled workloads will be deleted and recreated.

To safely rename a Flux Kustomization, first set spec.prune to false and sync the change on the cluster. To make sure that the change has been acknowledged by Flux, run flux export kustomization <name> and check that pruning is disabled. Finally, rename the Kustomization and re-enabled pruning. Flux will delete the old Kustomization and transfer ownership of the reconciled resources to the new Kustomization. You can run flux tree kustomization <new-name> to see which resources are managed by Flux.

Why are kubectl edits rolled back by Flux?

If you use kubectl to edit an object managed by Flux, all changes will be undone when kustomize-controller reconciles a Flux Kustomization containing that object.

In order for Flux to preserve fields added with kubectl, for example a label or annotation, you have to specify a field manager named flux-client-side-apply. For example, to manually add a label to a resource, do:

kubectl --field-manager=flux-client-side-apply label ...

Note that fields specified in Git will always be overridden, the above procedure works only for adding new fields that don’t overlap with the desired state.

Rollout restarts add a “restartedAt” annotation, which flux will remove, re-deploying the pods. To complete a rollout restart successfully, use the flux-client-side-apply field manager e.g.:

kubectl --field-manager=flux-client-side-apply rollout restart ...

Should I be using Kustomize remote bases?

For security and performance reasons, it is advised to disallow the usage of remote bases in Kustomize overlays. To enforce this setting, platform admins can set the --no-remote-bases=true flag for kustomize-controller.

Note: This flag prevents the usage of remote bases only, i.e. a Git repository or a sub directory. It does not affect the usage of remote targets pointing to a single file.

When using remote bases, the manifests are fetched over HTTPS from their remote source on every reconciliation e.g.:

# infra/kyverno/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - https://github.com/stefanprodan/podinfo/deploy/overlays/dev?ref=master

To take advantage of Flux’s verification and caching features, you can replace the kustomization.yaml with a Flux source definition:

apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: OCIRepository
metadata:
  name: kyverno
  namespace: flux-system
spec:
  interval: 60m
  url: oci://ghcr.io/kyverno/manifests/kyverno
  ref: # pull the latest patch release evey hour
    semver: 1.8.x
  verify: # enable Cosign keyless verification
    provider: cosign

Then to reconcile the manifests on a cluster, you’ll use the ones from the verified source:

apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: kyverno
  namespace: flux-system
spec:
  interval: 360m
  prune: true
  wait: true
  timeout: 5m
  sourceRef:
    kind: OCIRepository
    name: kyverno
  path: ./
  kubeConfig:
    secretRef:
      name: staging-cluster

Should I be using Kustomize Helm chart plugin?

Due to security and performance reasons, Flux does not allow the execution of Kustomize plugins which shell-out to arbitrary binaries insides the kustomize-controller container.

Instead of using Kustomize to deploy charts, e.g.:

# infra/kyverno/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namespace: kyverno
resources:
  - kyverno-namespace.yaml
helmCharts:
- name: kyverno
  valuesInline:
    networkPolicy:
      enabled: true
  releaseName: kyverno
  version: 2.6.0
  repo: https://kyverno.github.io/kyverno/

You can take advantage of Flux’s OCI and native Helm features, by replacing the kustomization.yaml with a Flux Helm definition:

apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmRepository
metadata:
  name: kyverno
  namespace: flux-system
spec:
  interval: 6h
  url: oci://ghcr.io/kyverno/charts
  type: oci
---
apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: kyverno
  namespace: flux-system
spec:
  interval: 6h
  releaseName: kyverno
  targetNamespace: kyverno
  install:
    createNamespace: true
  chart:
    spec:
      chart: kyverno
      version: 2.6.0
      interval: 6h
      sourceRef:
        kind: HelmRepository
        name: kyverno
  values:
    networkPolicy:
      enabled: true

What is the behavior of Kustomize used by Flux?

We referred to the Kustomize v5 CLI flags here, so that you can replicate the same behavior using kustomize build:

---enable-alpha-plugins is disabled by default, so it uses only the built-in plugins.
--load-restrictor is set to LoadRestrictionsNone, so it allows loading files outside the dir containing kustomization.yaml.

To replicate the build and apply dry run locally:

kustomize build --load-restrictor=LoadRestrictionsNone . \
| kubectl apply --server-side --dry-run=server -f-

kustomization.yaml validation

To validate changes before committing and/or merging, a validation utility script is available, it runs kustomize locally or in CI with the same set of flags as the controller and validates the output using kubeconform.

How to patch CoreDNS and other pre-installed addons?

To patch a pre-installed addon like CoreDNS with customized content, add a shell manifest with only the changed values and kustomize.toolkit.fluxcd.io/ssa: merge annotation into your Git repository.

Example CoreDNS with custom replicas, the spec.containers[] empty list is needed for the patch to work and will not override the existing containers:

---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    k8s-app: kube-dns
  annotations:
    kustomize.toolkit.fluxcd.io/prune: disabled
    kustomize.toolkit.fluxcd.io/ssa: merge
  name: coredns
  namespace: kube-system
spec:
  replicas: 5
  selector:
    matchLabels:
      eks.amazonaws.com/component: coredns
      k8s-app: kube-dns
  template:
    metadata:
      labels:
        eks.amazonaws.com/component: coredns
        k8s-app: kube-dns
    spec:
      containers: []

Note that only non-managed fields should be modified else there will be a conflict with the manager of the fields (e.g. eks). For example, while you will be able to modify affinity/antiaffinity fields, the manager (e.g. eks) will revert those changes and that might not be immediately visible to you (with EKS that would be an interval of once every 30 minutes). The deployment will go into a rolling upgrade and Flux will revert it back to the patched version.

Helm questions

Can I use Flux HelmReleases without GitOps?

Yes, you can install the Flux components directly on a cluster and manage Helm releases with kubectl.

Install the controllers needed for Helm operations with flux:

flux install \
--namespace=flux-system \
--network-policy=false \
--components=source-controller,helm-controller

Create a Helm release with kubectl:

cat << EOF | kubectl apply -f -
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmRepository
metadata:
  name: bitnami
  namespace: flux-system
spec:
  interval: 30m
  url: https://charts.bitnami.com/bitnami
---
apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: metrics-server
  namespace: kube-system
spec:
  interval: 60m
  releaseName: metrics-server
  chart:
    spec:
      chart: metrics-server
      version: "^5.x"
      sourceRef:
        kind: HelmRepository
        name: bitnami
        namespace: flux-system
  values:
    apiService:
      create: true
EOF

Based on the above definition, Flux will upgrade the release automatically when Bitnami publishes a new version of the metrics-server chart.

How do I set local overrides to a Helm chart?

Lets assume we have a common HelmRelease definition we use as a base and we we need to further customize it e.g per cluster, tenant, environment and so on:

apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: podinfo
  namespace: podinfo
spec:
  releaseName: podinfo
  chart:
    spec:
      chart: podinfo
      sourceRef:
        kind: HelmRepository
        name: podinfo
  interval: 50m
  install:
    remediation:
      retries: 3

and we want to override the chart version per cluster for example to gradually roll out a new version. We have couple options:

Using Kustomize patches

---
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: apps
  namespace: flux-system
spec:
  interval: 30m
  retryInterval: 2m
  sourceRef:
    kind: GitRepository
    name: flux-system
  path: ./apps/production
  prune: true
  wait: true
  timeout: 5m0s
  patches:
    - patch: |-
        - op: replace
          path: /spec/chart/spec/version
          value: 4.0.1        
      target:
        kind: HelmRelease
        name: podinfo
        namespace: podinfo

Using Kustomize variable substitution

apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: podinfo
  namespace: podinfo
spec:
  releaseName: podinfo
  chart:
    spec:
      chart: podinfo
      version: ${PODINFO_CHART_VERSION:=6.2.0}
      sourceRef:
        kind: HelmRepository
        name: podinfo
  interval: 50m
  install:
    remediation:
      retries: 3

To enable the replacement of the PODINFO_CHART_VERSION variable with a different version than the 6.2.0 default, specify postBuild in the Kustomization:

apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: apps
  namespace: flux-system
spec:
  interval: 30m
  retryInterval: 2m
  sourceRef:
    kind: GitRepository
    name: flux-system
  path: ./apps/production
  prune: true
  wait: true
  timeout: 5m0s
  postBuild:
    substitute:
      PODINFO_CHART_VERSION: 6.3.0

Flux v1 vs v2 questions

What are the differences between v1 and v2?

Flux v1 is a monolithic do-it-all operator; it has reached its EOL and has been archived. Flux v2 separates the functionalities into specialized controllers, collectively called the GitOps Toolkit.

You can find a detailed comparison of Flux v1 and v2 features in the migration FAQ.

How can I migrate from v1 to v2?

The Flux community has created guides and example repositories to help you migrate to Flux v2:

Last modified 2023-09-29: Explain how to use the prune annotation when moving resources (bd8b54e)