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
   

   NOTE 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

2. Create the file structure

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

3. Create the base deployment yaml and open to edit

   vi sample-app/base/deployment.yaml
   

4. 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
   

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

   vi sample-app/base/kustomization.yaml
   

6. 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
   

7. Add the following contents and save

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

8. Create an overlay kustomization file and open to edit

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

9. Add the following contents

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

10. 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

Bonus round!

1. 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

1. kustomize build sample-app/overlays/production
   

   This should spit the following out 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