Understanding Kustomize and Its Differences from Helm

Kustomize is a tool for customizing Kubernetes YAML configurations. It allows you to manage different environments (e.g., development, staging, production) without duplicating YAML files. Kustomize is built into kubectl, making it easy to use alongside other Kubernetes tools. This guide will explain what Kustomize is, how it works, and how it differs from Helm, another popular Kubernetes package manager.

What is Kustomize?

Kustomize enables users to create a base configuration and then apply overlays to customize that configuration for different environments. It uses a declarative approach, allowing you to define how resources should be modified without changing the original YAML files.

Key Features of Kustomize:

• Overlay Management: Easily manage different configurations for various environments using overlays.
• Resource Composition: Combine multiple resources into a single configuration.
• Patch Support: Apply strategic merge patches or JSON patches to modify existing resources.
• No Templating: Kustomize does not use templating; it modifies existing YAML files directly.

How Kustomize Works

Kustomize operates by defining a kustomization.yaml file that specifies the resources to be customized and any patches or overlays to apply. Below is an example of how to use Kustomize.

Example of Kustomize Usage:

        
# Create a base deployment.yaml
cat <<eof> deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: my-app
          image: my-app:latest
EOF

# Create a kustomization.yaml file
cat <<eof> kustomization.yaml
resources:
  - deployment.yaml
EOF

# Apply the kustomization
kubectl apply -k .
        </eof></eof>    

What is Helm?

Helm is a package manager for Kubernetes that simplifies the deployment and management of applications through the use of Helm charts. Charts are pre-configured packages of Kubernetes resources that can be easily installed, upgraded, or deleted.

Key Features of Helm:

• Package Management: Helm allows you to package Kubernetes resources into charts for easy distribution and installation.
• Templating: Helm uses Go templates to allow dynamic configuration of resources based on user-defined values.
• Version Control: Helm supports versioning of charts, making it easy to roll back to previous versions.
• Dependency Management: Helm can manage dependencies between charts, allowing you to define complex applications easily.

How Helm Works

Helm uses a chart structure that includes a Chart.yaml file, templates, and a values file. Below is an example of how to use Helm.

Example of Helm Usage:

        
# Create a new Helm chart
helm create my-app

# Modify the values.yaml file to set the image
cat <<eof> my-app/values.yaml
image:
  repository: my-app
  tag: latest
EOF

# Install the Helm chart
helm install my-app ./my-app
        </eof>    

Differences Between Kustomize and Helm

Conclusion

Both Kustomize and Helm are powerful tools for managing Kubernetes resources, but they serve different purposes. Kustomize is ideal for customizing existing configurations without duplication, while Helm excels in packaging and distributing applications. Depending on your needs, you may choose one over the other or even use them together to leverage their strengths.