DEMO Image Automation Controller Repository

In this tutorial, we’ll use Flux’s ImageRepository Custom Resource Definition (CRD) to connect to a Docker Hub repository and fetch image tags automatically. Flux provides three subcommands under flux create image: policy, repository, and update. We’ll focus on the repository subcommand to set up continuous image discovery and metadata polling.

Overview of Flux Image Commands

Subcommand	Purpose	Example
policy	Define rules for selecting image tags	`flux create image policy my-policy --image nginx`
repository	Register an image source for Flux to scan	`flux create image repository my-repo --image nginx`
update	Manually bump image tags on Kubernetes objects	`flux create image update deployment/my-app --policy my-policy`

1. Create an ImageRepository

First, verify the available options:

root ~/block-buster/flux-clusters/dev-cluster main
➜ flux create image
policy       repository   update

Define an ImageRepository manifest that points to your Docker Hub image and polls it at a regular interval:

apiVersion: image.toolkit.fluxcd.io/v1beta2
kind: ImageRepository
metadata:
  name: bb-app-image-repo
  namespace: flux-system
spec:
  image: docker.io/siddharth67/bb-app-flux-demo
  interval: 10s

Note

Make sure your Git repository includes the flux-system namespace and the Flux controllers are installed before applying this manifest.

You can export this manifest directly with the Flux CLI:

root ~/block-buster/flux-clusters/dev-cluster main
➜ flux create image repository bb-app-image-repo \
    --image docker.io/siddharth67/bb-app-flux-demo \
    --interval 10s \
    --export > bb-app-image-repo.yaml

Commit and push the YAML to your Git repository, then trigger reconciliation:

➜ flux reconcile source git flux-system
✔ GitRepository annotated
✔ waiting for GitRepository reconciliation
✔ fetched revision main@sha1:dc9922e7f45b3bcd8d085e68766869b15a17919c

Verify the repository registration and initial scan:

➜ flux get image all
NAME                         LAST SCAN                   SUSPENDED   READY   MESSAGE
imagerepository/bb-app-image-repo 2023-04-06T19:19:02+05:30 False       True    successful scan: found 1 tags

At this point, Flux has detected the 7.8.0 tag in your Docker Hub repository.

2. Update the Application and Push a New Tag

2.1 Modify the PHP Source

Open bb-app-source/src/index.php (and level2.php) and update the styling as well as the app version to 7.8.1:

<?php
echo "<table class='container'>
<tr>
  <td style='background-color:#222222; width:25%'><h2>&nbsp; Pod Name</h2></td>
  <td style='background-color:#222222'><h3>&nbsp;". getenv("MY_POD_NAME") ."</h3></td>
</tr>
<tr>
  <td style='background-color:#3C3C3C'><h2>&nbsp; Pod IP</h2></td>
  <td style='background-color:#3C3C3C'><h3>&nbsp;". getenv("MY_POD_IP") ."</h3></td>
</tr>
<tr>
  <td style='background-color:#222222'><h2>&nbsp; Namespace</h2></td>
  <td style='background-color:#222222'><h3>&nbsp;". getenv("MY_POD_NAMESPACE") ."</h3></td>
</tr>
<tr>
  <td style='background-color:#3C3C3C'><h2>&nbsp; K8S Node</h2></td>
  <td style='background-color:#3C3C3C'><h3>&nbsp;". getenv("MY_NODE_NAME") ."</h3></td>
</tr>
<tr>
  <td style='background-color:#222222'><h2>&nbsp; App Version</h2></td>
  <td style='background-color:#222222'><h3>&nbsp;7.8.1 (minor color change)</h3></td>
</tr>
<tr>
  <td style='background-color:#3C3C3C'><h2>&nbsp; What’s New</h2></td>
  <td style='background-color:#3C3C3C'><h3>&nbsp;BugFix – HighScore is persisted</h3></td>
</tr>
</table>";
?>

Warning

Be sure to update all source files (e.g., level2.php) to keep version consistency.

2.2 Build and Push the Docker Image

Ensure your Dockerfile includes the necessary PHP extensions and copies your application files:

FROM php:7.4-apache
RUN docker-php-ext-install mysqli
COPY highscore.php index.php level2.php /var/www/html/
COPY images /var/www/html/images
EXPOSE 80

Build and tag the new image version 7.8.1:

root ~/block-buster/flux-clusters/dev-cluster main
cd ../bb-app-source/src
➜ docker build -t siddharth67/bb-app-flux-demo:7.8.1 .

Push the updated image to Docker Hub:

➜ docker push siddharth67/bb-app-flux-demo:7.8.1

After pushing, verify on Docker Hub that the 7.8.1 tag is available.

3. Flux Scans the New Tag

Trigger an immediate reconciliation for the ImageRepository:

➜ flux reconcile image repository bb-app-image-repo

Re-run the flux get image command to confirm that two tags are now detected:

➜ flux get image all
NAME                         LAST SCAN                   SUSPENDED   READY   MESSAGE
imagerepository/bb-app-image-repo 2023-04-06T19:23:30+05:30 False       True    successful scan: found 2 tags

Alternatively, inspect the resource via kubectl:

kubectl -n flux-system get imagerepositories.image.toolkit.fluxcd.io bb-app-image-repo -o yaml

status:
  lastScanResult:
    latestTags:
      - "7.8.1"
      - "7.8.0"
    tagCount: 2

Even though two tags exist, your Deployment is still running the old version:

kubectl -n a-demo get deploy block-buster -o wide

NAME           READY UP-TO-DATE AVAILABLE AGE   CONTAINERS IMAGES                             SELECTOR
block-buster   1/1   1          1         15m   app        siddharth67/bb-app-flux-demo:7.8.0 app=block-buster

Next Steps

Automate tag selection and deployment by creating a Flux ImagePolicy that matches your versioning scheme (e.g., semver or regex). This will ensure your Kubernetes workload always uses the latest approved image.