Demo Initialize DockerHub

In this lesson you’ll push a Docker image to Docker Hub and update Flux-managed manifests to deploy that image to a Flux-enabled Kubernetes cluster. The workflow shows how to:

Log in to Docker Hub
Pull an existing upstream image
Tag and push that image to your Docker Hub repository
Update a Kubernetes Deployment to reference the pushed image
Create Flux GitRepository and Kustomization objects to deploy the manifest
Verify the application is running and confirm the bug fix present in version 7.8.0

Quick links:

Flux docs: https://fluxcd.io/docs/
Docker Hub: https://hub.docker.com/
Kubernetes docs: https://kubernetes.io/docs/

Prerequisites

Requirement	Why
Docker Hub account	Needed to host container images. Create one at `https://hub.docker.com`.
Docker installed	Required to pull, tag, and push images.
Flux-enabled cluster and Flux CLI	Flux will deploy the manifests; Flux CLI helps create GitRepository/Kustomization objects.

Make sure to replace siddharth67 in the examples below with your own Docker Hub username wherever applicable. For improved security, prefer using a Docker access token instead of your password when running docker login.

Never commit Docker credentials or access tokens to git. Use secret management or CI/CD secret stores when automating image pushes.

1) Log in to Docker Hub

If you are authenticated to another registry, log out first, then log in to Docker Hub:

# log out any current registry
docker logout

# log in to Docker Hub (use a personal access token if possible)
docker login
# Enter your Docker Hub username and password or token when prompted

Successful login will show:

Login Succeeded

2) Pull the existing image

Pull the upstream image used as the source for this demo:

docker pull siddharth67/block-buster-dev:7.8.0

Example output (condensed):

7.8.0: Pulling from siddharth67/block-buster-dev
Digest: sha256:cf5c4e2a9ef6ad48798dd0ae41e3a39565eb2bce7dbc69f239a22804ee78f691
Status: Image is up to date for docker.io/siddharth67/block-buster-dev:7.8.0

3) Tag the image for your Docker Hub repository

Tag the pulled image to point at your Docker Hub repository and the desired image name. Replace your-username with your Docker Hub username:

docker tag siddharth67/block-buster-dev:7.8.0 your-username/bb-app-flux-demo:7.8.0

Instructor example (preserves original username for clarity):

docker tag siddharth67/block-buster-dev:7.8.0 siddharth67/bb-app-flux-demo:7.8.0

4) Push the image to Docker Hub

Push the tagged image up to your Docker Hub repository:

docker push your-username/bb-app-flux-demo:7.8.0

Example push output (condensed):

The push refers to repository [docker.io/siddharth67/bb-app-flux-demo]
7.8.0: Pushed
digest: sha256:cf5c4e2a9ef6ad48798dd0ae41e3a39565eb2bce7dbc69f239a22804ee78f691 size: 3662

After the push completes, verify the 7.8.0 tag is visible in your Docker Hub repository UI for your-username/bb-app-flux-demo.

5) Update the deployment manifest

Edit the Deployment YAML stored in the bb-app-source repository (branch 8-demo) so the image: field points to your pushed image. This minimal example highlights the image: field to change:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: bb-app
  namespace: 8-demo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: bb-app
  template:
    metadata:
      labels:
        app: bb-app
    spec:
      containers:
        - name: app
          image: siddharth67/bb-app-flux-demo:7.8.0
          imagePullPolicy: Always
          resources:
            requests:
              memory: "10Mi"
              cpu: "10m"

Before committing, replace siddharth67 with your Docker Hub username in the image: field.

6) Publish manifests and create Flux objects

The demo uses two repositories:

A source repo that contains application manifests (bb-app-source branch 8-demo)
A Flux repo that contains Flux GitRepository and Kustomization manifests (e.g., flux-clusters)

From the flux-clusters/dev-cluster directory, create a GitRepository source and Kustomization for the 8-demo branch. The commands below use --export to save the generated objects to YAML files:

# from the flux-clusters/dev-cluster directory
flux create source git 8-demo-source-git-bb-app \
  --url https://github.com/sidd-harth-2/bb-app-source \
  --branch 8-demo \
  --timeout 10s \
  --export > 8-demo-source-git-bb-app.yml

flux create kustomization 8-demo-kustomize-git-bb-app \
  --source GitRepository/8-demo-source-git-bb-app \
  --prune true \
  --interval 100s \
  --target-namespace 8-demo \
  --path manifests \
  --export > 8-demo-kustomize-git-bb-app.yml

Example exported manifests: GitRepository (8-demo-source-git-bb-app.yml)

apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: GitRepository
metadata:
  name: 8-demo-source-git-bb-app
  namespace: flux-system
spec:
  interval: 1m0s
  ref:
    branch: 8-demo
  url: https://github.com/sidd-harth-2/bb-app-source

Kustomization (8-demo-kustomize-git-bb-app.yml)

apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
kind: Kustomization
metadata:
  name: 8-demo-kustomize-git-bb-app
  namespace: flux-system
spec:
  interval: 1m40s
  path: ./manifests
  prune: true
  sourceRef:
    kind: GitRepository
    name: 8-demo-source-git-bb-app
  targetNamespace: 8-demo

Commit and push these files to the repository monitored by Flux (for example, your flux-clusters repo). To accelerate reconciliation after pushing, run:

flux reconcile source git 8-demo-source-git-bb-app --with-source
flux reconcile kustomization 8-demo-kustomize-git-bb-app

7) Verify deployment

Confirm Flux created the 8-demo namespace and applied the manifests:

kubectl get namespaces
kubectl get all -n 8-demo
# expect: Pod, Service, Deployment, ReplicaSet in Running/Ready state

The application in this demo is exposed on a NodePort. The demo uses:

http://localhost:30008

Open that URL in your browser and exercise the app. Version 7.8.0 includes a bug fix: the high score is persisted to the database.

A screenshot of a web-based game titled "BLOCK BUSTER" showing deployment info at the top (pod name, IP, namespace, node, app version) and a large dark play area with "PRESS START" in the center and a green "START GAME" button at the bottom.

In the demo, after pressing Start and ending the game quickly, a score like 1200 will be persisted and displayed in the high score field after restarting — confirming the fix in 7.8.0.

Next steps

Automate image updates with Flux Image Automation Controller and an ImageRepository object to fetch tags from Docker Hub automatically.
Integrate CI to build and push images and then let Flux detect and roll out updates.

Useful command reference:

Action	Command / Example
Push image	`docker push your-username/bb-app-flux-demo:7.8.0`
Reconcile GitRepository	`flux reconcile source git 8-demo-source-git-bb-app --with-source`
Reconcile Kustomization	`flux reconcile kustomization 8-demo-kustomize-git-bb-app`
Inspect namespace	`kubectl get all -n 8-demo`

For more on Flux GitRepository and Kustomization, see the Flux documentation: https://fluxcd.io/docs/ That’s all for this demo.

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

Demo Initialize DockerHub

Prerequisites

1) Log in to Docker Hub

2) Pull the existing image

3) Tag the image for your Docker Hub repository

4) Push the image to Docker Hub

5) Update the deployment manifest

6) Publish manifests and create Flux objects

7) Verify deployment

Next steps

Watch Video

​Prerequisites

​1) Log in to Docker Hub

​2) Pull the existing image

​3) Tag the image for your Docker Hub repository

​4) Push the image to Docker Hub

​5) Update the deployment manifest

​6) Publish manifests and create Flux objects

​7) Verify deployment

​Next steps

Watch Video

Prerequisites

1) Log in to Docker Hub

2) Pull the existing image

3) Tag the image for your Docker Hub repository

4) Push the image to Docker Hub

5) Update the deployment manifest

6) Publish manifests and create Flux objects

7) Verify deployment

Next steps