Build a container image inside a Kubernetes cluster and push it to IBM Cloud Container Registry

Learn how to build a source into a container image from a Dockerfile inside a Kubernetes cluster and push the image to IBM Cloud Container Registry; all of this using Google’s Kaniko tool.

So, What is Kaniko?

Kaniko is a tool to build container images from a Dockerfile, inside a container or Kubernetes cluster.

Kaniko logo

If you don’t have a Kubernetes cluster with Knative and Istio installed, it’s recommended to follow the instructions mentioned in my previous post that also introduces you to the components of Knative — Install Knative with Istio and deploy an app on IBM Cloud

This tutorial uses the Build and Serving components of Knative to orchestrate an end-to-end deployment.

A Knative build extends Kubernetes and utilizes existing Kubernetes primitives to provide you with the ability to run on-cluster container builds from source. For example, you can write a build that uses Kubernetes-native resources to obtain your source code from a repository, build it into container a image, and then run that image.

Knative Serving builds on Kubernetes and Istio to support deploying and serving of serverless applications and functions. Serving is easy to get started with and scales to support advanced scenarios.

What is a Build Template?

A BuildTemplateis one of the key features of Knative build used to defined reusable templates and encapsulates a shareable build process with some limited parameterization capabilities. A set of curated and supported build templates is available in the build-templates repo. We will be using the Kaniko BuildTemplate in the tutorial

Kaniko doesn’t depend on a Docker daemon and executes each command within a Dockerfile completely in userspace. This enables building container images in environments that can’t easily or securely run a Docker daemon, such as a standard Kubernetes cluster.

Let’s start by creating a Kaniko BuildTemplate and saving this as kaniko.yaml

Parameters

• IMAGE: The Docker image name to apply to the newly built image.(required) Replace <region>and <namespace> with appropriate values. Remember these values as you have to replace these values in the YAMLscripts below.
• DOCKERFILE: The path to the Dockerfile to execute (default: ./Dockerfile)

Note: To check your region, run ibmcloud cr regionand to setup a new namespace, refer this link

If you are looking for a sample with Dockerfile, try https://github.com/VidyasagarMSC/knative-deploy

Kaniko builds an image and pushes it to the destination defined as a parameter. In order to properly authenticate to the remote container registry (IBM Cloud Container Registry), the build needs to have the proper credentials. This is achieved using a build ServiceAccount.

Before this, let’s define a Secret containing the username and password that the build should use to authenticate(basic) to IBM Cloud Container Registry:

For <password>, run the below command

$ ibmcloud cr token-add --description “This is a token” --non-expiring --readwrite
Returns: 
Token identifier 58669dd6–3ddd-5c78–99f9-ad0a5aabd9ad 
Token            <token_value>

Use the returned token_value as your password and save the file as secret.yaml . For more details related to token, refer this link

Now you can create aserviceaccount.yaml file with the ServiceAccount using the secret as shown below

Let’s use ServiceAccount in our Build and save the file asbuild.yaml

Execute the build

$ kubectl apply --filename kaniko.yaml
$ kubectl apply --filename secret.yaml
$ kubectl apply --filename serviceaccount.yaml
$ kubectl apply --filename build.yaml

The build should have been kicked off. Let’s take a look.

Runningkubectl get pods , you should see a pod named kaniko-build with a postfix(say XXXXX).

For logs, run this command

$ kubectl logs kaniko-build-XXXXX -c build-step-build-and-push

If everything runs as expected, you should see the image in the list when you run the below command

$ ibmcloud cr images

Hurray!! you have just created a container image without a Docker Daemon. Let’s deploy and serve the app so that we can access it from anywhere. For this, lets create a service.yaml file:

Execute the service

$ kubectl apply --filename service.yaml

To find the IP address for your service, use kubectl get svc knative-ingressgateway -n istio-system to get the ingress IP for your cluster. If your cluster is new, it may take sometime for the service to get assigned an external IP address.

$ export IP_ADDRESS=$(kubectl get svc knative-ingressgateway --namespace istio-system --output 'jsonpath={.status.loadBalancer.ingress[0].ip}')

To find the URL for your service, use kubectl get services.serving.knative.dev knative-node-app --output jsonpath='{.status.domain}'

$ export HOST_URL=$(kubectl get services.serving.knative.dev knative-node-kaniko  --output jsonpath='{.status.domain}')

Now you can make a request to your app to see the result.

$ curl -H "Host: ${HOST_URL}" http://${IP_ADDRESS}
Response: Kaniko Node App running on IBM Cloud

For a sample with all these YAML templates and scripts, refer https://github.com/VidyasagarMSC/knative-deploy/tree/master/kaniko

Clean up

Run the below command to remove the sample app from your cluster

$ kubectl delete --filename service.yaml

To delete other secret,ServiceAccount and Build

$ kubectl delete --filename build.yaml
$ kubectl delete --filename serviceaccount.yaml
$ kubectl delete --filename secret.yaml
$ kubectl delete --filename kaniko.yaml

To delete the cluster (removes everything), enter the following command:

$ ibmcloud cs cluster-rm $CLUSTER_NAME