MINC: Speed Up Local K8s Dev
Developers working locally often seek a fast inner loop for coding, building, and testing their OCI images and Kubernetes applications.
For instance, when testing a new image in a Kubernetes pod, the image must be accessible either by pushing it to a private or public registry or by ensuring it's available on the Kubernetes cluster nodes. This often requires additional commands such as kind load docker-image, minikube cache add <image>, or publishing the image to a third-party registry.
In this blog post, we’ll introduce a new extension called MINC (MicroShift IN Container), which provides a MicroShift cluster running within an existing Podman Machine environment.
Introduction
A previous blog post outlines various methods to improve the inner loop using Kind or Minikube. While these approaches can enhance performance, there are still gaps and certain complexities involved. Achieving a seamless workflow where an image is built with Podman and immediately available in the cluster—often requires additional steps or tricky configurations.
podman, kubernetes/cri-o and MicroShift
The CRI-O project implements the CRI interface and reuses image management from containers/image project and handles storage using containers/storage project.
Podman uses these same libraries to read and write container images, storing them in the /var/lib/containers directory.
The MINC extension launches a MicroShift cluster in a more efficient way for developers than previous deployments. Unlike the OpenShift Local extension, which sets up a separate virtual machine (VM), MINC (Microshift IN Container) runs a container inside your existing Podman Machine (on Windows or macOS). This avoids running two VMs, one for Kubernetes and another for Podman.
A key benefit is that the MINC container shares Podman’s image storage. When you build an image with Podman, it's instantly available in the cluster, no uploading or copying required.
Make sure the machine is running in rootful mode, or create a new one using the --rootful option.
Creating a Local Kubernetes/MicroShift Cluster
- Create the MicroShift cluster
In the Resources view, click the MINC card and select "Create new…". For now, no customization is needed—just click "Next". The cluster will start automatically.
-
Verify that now you see in bottom left in the status bar
microshiftas the default Kubernetes context and if you go in the left navbar in the Kubernetes section you can see in the Nodes entry the MicroShift node. -
Verify
kubectlsetup using a CLI
MINC updates your $HOME/.kube/config file with a new microshift entry. Check in the bottom left of the status bar, you should see a microshift entry as the default Kubernetes context.
Try listing all pods:
kubectl get -A pods
Example output:
NAMESPACE NAME READY STATUS
kube-flannel kube-flannel-ds-wjn2f 1/1 Running
kube-proxy kube-proxy-jh7r8 1/1 Running
kube-system csi-snapshot-controller-8d97d878f-l6q6j 1/1 Running
openshift-dns dns-default-zvdw9 2/2 Running
openshift-dns node-resolver-84twk 1/1 Running
openshift-ingress router-default-54c5757547-4jnfd 1/1 Running
openshift-service-ca service-ca-7977bdc4d4-ssjq2 1/1 Running
Create a Hello World container image
Create a Containerfile
FROM nginx
RUN echo '<!DOCTYPE html><html><head><title>Hello</title></head><body><h1>Hello from MINC</h1></body></html>' \
> /usr/share/nginx/html/index.html
Or quickly create it with:
echo 'FROM nginx:alpine
RUN echo "<!DOCTYPE html><html><head><title>Hello</title></head><body><h1>Hello from MINC</h1></body></html>" > /usr/share/nginx/html/index.html' > Containerfile
Then, using Podman Desktop, build the image providing the name minc/nginx:hello-world.
Verify Image in the MicroShift Cluster
Inside the MicroShift container, run:
crictl images | grep hello
You should see something like:
docker.io/minc/nginx hello-world e7032b219ab03 51.1MB
The image is now available in the MicroShift cluster.
Create a Pod from the UI
Click on the play button from the image to start a new container. Then select the container and click on "Create Pod".
Deploy a pod from this image using the CLI
Use kubectl to deploy a pod from the image:
kubectl run hello-world-pod --image=minc/nginx:hello-world --port=80
To check if the pod is running, use:
kubectl get pods
Expected output:
kubectl get pods
NAME READY STATUS RESTARTS AGE
hello-world-pod 1/1 Running 0 6s
Deploy this podman Pod to Kubernetes/MINC
Select the pod and click on Deploy to Kubernetes... in the Kebab menu.
Your Pod is now deployed to the MINC cluster.
If you want to use the CLI/manual steps :
Create a Service for the Pod using the CLI
Expose the pod with a service:
kubectl expose pod hello-world-pod --port=80 --target-port=80 --name=hello-world-service
Create a Route (Requires oc CLI)
Assuming the oc CLI (OpenShift client) is available in your PATH, create a route:
oc create route edge hello-world-route --service svc/hello-world-service --port 80 --wildcard-policy=None
To list all routes:
oc get routes
Access the Nginx Container
Clicking on the route in the UI will redirect you to the page.
Without the UI it's also possible to get that information.
Check that the nginx container is reachable using the route. Use the -k flag with curl to ignore the self-signed certificate warning:
curl -k "https://$(oc get route hello-world-route -ojsonpath='{.status.ingress[0].host}'):9443"
You can also open the URL in your browser (you’ll need to ignore the self-signed certificate warning):
open "https://$(oc get route hello-world-route -ojsonpath='{.status.ingress[0].host}'):9443"
You should see the message: "Hello from MINC" 🎉
This confirms that your inner development loop is working. Once the image is built, it’s instantly available in the cluster.
Video walkthrough
Conclusion
Using MINC and the MINC extension significantly reduces the turnaround time between building and testing container images.
Have feedback? Share it on the MINC extension issue tracker