Kustomize Lab

Lab Overview

In this lab we use kustomize CLI tool for templating kubernetes .yaml files, but first we will build out the directory structure and populate the necessary files.

Finally, we will compare the files that the kustomize tool generated to understand how kustomize is implemented

Kustomize

Lab

1. Verify kustomize is installed

   kustomize version
   which kustomize
   

Warning

For Ubuntu users (if kustomize was installed via snap) you’ll see errors, so let’s verify

The which command tells you the path where the kustomize cli tool is installed

If you see snap in the path, uninstall it and reinstall using the directions on this page

1. Create the file structure

   cd ~/Desktop/configlabs
   mkdir -p sample-app/base
   mkdir -p sample-app/overlays/development
   mkdir -p sample-app/overlays/production
   

2. Create the base deployment yaml and open to edit

   vi sample-app/base/deployment.yaml
   

3. Add base pod to the file and save

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: hello-world
   spec:
     replicas: 1
     selector:
       matchLabels:
        app: hello-world
     template:
       metadata:
         labels:
           app: hello-world
       spec:
         containers:
         - name: hello-world
           image: nginx
           resources:
             limits:
               memory: "128Mi"
               cpu: "500m"
           ports:
           - containerPort: 80
   

4. Create the base kustomization.yaml and open to edit

   vi sample-app/base/kustomization.yaml
   

5. Add the following contents and save

   # Specifies the files to include when kustomize builds the application
   resources:
   - deployment.yaml
   

   Create an overlay file and open to edit

   vi sample-app/overlays/development/replica_count.yaml
   

6. Add the following contents and save

   # Overlay to increase the replicaCount
   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: hello-world
   spec:
     replicas: 3
   

7. Create an overlay kustomization file and open to edit

   vi sample-app/overlays/development/kustomization.yaml
   

8. Add the following contents

   # Specifies the base files
   bases:
   - ../../base
   
   # Specifies overrides to the base files
   patches:
   - replica_count.yaml
   

9. Generate Kustomize output

   kustomize build sample-app/overlays/development 
   cat sample-app/base/deployment.yaml
   

   Compare the 2 outputs and notice the replicaCount of 3 was overlaid onto the base file

10. Generate a production deployment with kustomize

    Create the kustomization.yaml and replica_count.yaml for production environment

    vi sample-app/overlays/production/kustomization.yaml
    

    Add the following contents

    bases:
    - ../../base
    
    patches:
    - replica_count.yaml
    

    vi sample-app/overlays/production/replica_count.yaml
    

    Add the following contents

    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: hello-world
    spec:
      replicas: 200
    

Now create the deployment file for our production environment

  kustomize build sample-app/overlays/production

This should output the following to the terminal:

    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: hello-world
    spec:
      replicas: 200
      selector:
        matchLabels:
          app: hello-world
      template:
        metadata:
          labels:
            app: hello-world
        spec:
          containers:
          - image: nginx
            name: hello-world
            ports:
            - containerPort: 80
            resources:
              limits:
                cpu: 500m
                memory: 128Mi