Apply multi resources with one command is possible thanks to the Kustomize tool of K8s. In this post, we see how to use Kustomize tool to generate, modify and delete multi resources by applying only one command, useful when we have many configuration files to manage.

Resources

• Kubernetes cluster

• kubectl tool installed version 1.14 or higher configured to communicate with the cluster.

• Some Configuration files resources.

You can use these resources as examples:

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world-deployment
  labels:
    app: hello-world
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hello-world
  template:
    metadata:
      labels:
        app: hello-world
    spec:
      containers:
        - name: hello-world
          image: hello-world
          imagePullPolicy: IfNotPresent
          resources:
            requests:
              memory: "128Mi"
              cpu: "100m"
            limits:
              memory: "256Mi"
              cpu: "200m"
          ports:
            - containerPort: 80
          env:
            - name: "ENV_SCOPE"
              value: "lab"

servicie.yaml

apiVersion: v1
kind: Service
metadata:
  name: hello-world-service
spec:
  type: ClusterIP
  selector:
    app.kubernetes.io/name: hello-world-deployment
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80

Also, you can download these example files here.

Building Kustomize File

To use Kustomize we need to create a file called kustomize.yaml with the next content:

resources:
  - deployment.yaml
  - service.yaml

Generating Resources

To generate resources with Kustomize, we need to execute the command apply or create of kubectl tool with the argument -k or --kustomize to process a kustomization directory. This flag can't be used together with -f or -R, for example:

kubectl apply -k ./

This command process the resources in the current directory.

Using the example files with this structure:

We should do these steps

cd ./kustomize
kubectl create -k ./

You see something like that

service/hello-world-service created
deployment.apps/hello-world-deployment created

Deleting Resources

To delete resources you need to execute the command kubectl delete -k ./, this command will delete the resources previously created.

service "hello-world-service" deleted
deployment.apps "hello-world-deployment" deleted

Updating Resources

To update the resources is like creating resources with the difference that we used de word apply instead create, this will create or modify the resources defined, the modification has been applied only if exists any change between the current resources and the new ones.

References

• Declarative Management of Kubernetes Objects Using Configuration Files