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

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

1. Create the base deployment yaml and open to edit

vi sample-app/base/deployment.yaml

1. 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

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

vi sample-app/base/kustomization.yaml

1. 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

1. Add the following contents and save

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

1. Create an overlay kustomization file and open to edit

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

1. Add the following contents

# Specifies the base files
bases:
  - ../../base

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

1. 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. ```bash kustomize build sample-app/overlays/production

   This should spit the following out to the terminal:
   
   ```yaml
   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