Helm vs Kustomize: A Comprehensive Guide with Examples

Helm vs Kustomize: A Comprehensive Guide with Real-World Examples

Introduction

When it comes to Kubernetes application management, two popular tools stand out: Helm and Kustomize. Both tools aim to simplify Kubernetes deployments, but they take different approaches. Helm is often compared to a package manager for Kubernetes, while Kustomize offers a declarative way to manage Kubernetes configurations without templating. These tools empower organizations and individuals to deploy applications efficiently and ensure seamless management.

In this guide, we will explore the differences between Helm and Kustomize, their real-world use cases, and how to work with them using example configurations.

What is Helm?

Helm is a package manager for Kubernetes that allows developers to define, install, and upgrade applications using Helm Charts. A Helm Chart is a collection of YAML configuration files that define Kubernetes resources, making it easy to deploy and manage complex applications.

What Does Helm Offer?

• Templating system: Enables dynamic configuration using placeholders in YAML files.
• Dependency management: Allows defining dependencies between applications.
• Version control: Provides versioned application deployments.
• Release management: Simplifies rollback, upgrades, and rollouts.

What is Kustomize?

Kustomize is a configuration management tool that lets you customize raw Kubernetes YAML manifests without modifying the original files. Unlike Helm, Kustomize does not use templates; instead, it layers modifications on top of existing configurations.

What Does Kustomize Offer?

• Overlay-based configuration management: Apply patches and modifications without altering base YAML files.
• No templating: Uses a purely declarative approach without placeholders or variables.
• Native support in kubectl: Since Kubernetes 1.14, Kustomize is integrated into kubectl.
• Base and overlays structure: Allows for environment-specific configurations.

Helm vs. Kustomize: Key Differences

Feature	Helm	Kustomize
Approach	Templating with Go templates	Patch-based customization
Package Manager	Yes	No
Dependency Mgmt	Supports dependencies	No dependency management
Versioning	Supports versioned releases	No built-in versioning
Learning Curve	Moderate	Easy
Integration	Helm CLI	kubectl built-in

Example: Creating a Helm Chart

Let's create a simple Helm chart for a Nginx deployment.

Step 1: Install Helm

curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash

Step 2: Create a New Helm Chart

helm create my-nginx
cd my-nginx

Step 3: Modify the values.yaml

replicaCount: 2
image:
  repository: nginx
  tag: latest
service:
  type: ClusterIP
  port: 80

Step 4: Install the Helm Chart

helm install my-release ./my-nginx

Example: Using Kustomize for Nginx

Step 1: Create a Base Deployment

# base/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest

Step 2: Create an Overlay for Staging

# overlays/staging/kustomization.yaml
resources:
  - ../../base
patches:
  - target:
      kind: Deployment
      name: nginx
    patch: |-
      - op: replace
        path: "/spec/replicas"
        value: 5

Step 3: Apply the Kustomization

kubectl apply -k overlays/staging/

Helm vs. Kustomize with Real-World Examples

Scenario	Recommended Tool
Deploying packaged applications	Helm
Customizing existing YAML files	Kustomize
Managing application versions	Helm
Applying patches for different environments	Kustomize

Advanced Features of Helm and Kustomize

Helm

• Chart repositories: Store and share charts with helm repo.
• Hooks: Execute scripts at different points of deployment.
• Rollbacks: Easily revert to previous releases.

Kustomize

• Transformers: Modify labels, annotations, and images.
• Generators: Create ConfigMaps and Secrets dynamically.
• Strategic merge patches: Update YAML selectively.

Performance Comparison

• Helm: Uses client-side templating and may have performance overhead due to rendering.
• Kustomize: Directly applies YAML transformations and is generally faster for modifying existing configurations.

Challenges of Helm and Kustomize

Challenge	Helm	Kustomize
Complexity	Can be complex with templating	Requires structured overlays
Learning Curve	Moderate	Easier
YAML Duplication	Minimal	Can have duplication in overlays

Benefits of Helm and Kustomize

Benefit	Helm	Kustomize
Reusability	High	Moderate
Customization	Templating-based	Overlay-based
Adoption	Widely used in Kubernetes community	Built into kubectl

Conclusion

Helm and Kustomize both serve valuable roles in Kubernetes configuration management. Helm is best suited for deploying packaged applications with version control and dependencies, while Kustomize excels in modifying existing YAML manifests for different environments. Choosing the right tool depends on your use case, team workflow, and application complexity.

Would you use Helm, Kustomize, or combination of both? Let me know in the comments!

Until next blog post

Happy Helming and Kustming! 🎉