Helm & Kustomize

Exam relevance: CKA ✅ (Allowed resource: helm.sh/docs) | CKAD ✅ (Application Deployment — 20%)

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Helm — The Kubernetes Package Manager

Helm packages Kubernetes resources into charts — reusable, versioned bundles of YAML templates.

Core Concepts

Concept	Description
Chart	A package of Kubernetes resources (templates + values)
Release	A specific installation of a chart on a cluster
Repository	A collection of charts (like npm registry)
Values	Configuration that customizes a chart installation
Revision	A version of a release (created on install/upgrade)

Repository Management

# Add a repository
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx

# Update repo index (like apt update)
helm repo update

# List repos
helm repo list

# Search for charts
helm search repo nginx
helm search repo bitnami/mysql --versions      # Show all versions

# Search Artifact Hub (public charts)
helm search hub wordpress

Installing Charts

# Basic install
helm install my-release bitnami/nginx

# Install with custom values
helm install my-release bitnami/nginx --set replicaCount=3

# Install with values file
helm install my-release bitnami/nginx -f custom-values.yaml

# Install in a specific namespace
helm install my-release bitnami/nginx -n production --create-namespace

# Dry run (show what would be created without applying)
helm install my-release bitnami/nginx --dry-run

# Generate template output (just render YAML, don't install)
helm template my-release bitnami/nginx > rendered.yaml

# Install specific version
helm install my-release bitnami/nginx --version 15.0.0

Managing Releases

# List installed releases
helm list
helm list -A                               # All namespaces
helm list -n production

# Check release status
helm status my-release

# Get release values
helm get values my-release                 # User-supplied values
helm get values my-release --all           # All values (defaults + overrides)

# Get all manifests for a release
helm get manifest my-release

# Get release history
helm history my-release

Upgrading Releases

# Upgrade with new image tag
helm upgrade my-release bitnami/nginx --set image.tag=1.26

# Upgrade with values file
helm upgrade my-release bitnami/nginx -f updated-values.yaml

# Install if not exists, upgrade if exists
helm upgrade --install my-release bitnami/nginx

# Reuse previous values and add new ones
helm upgrade my-release bitnami/nginx --reuse-values --set replicaCount=5

Rollback

# View history
helm history my-release
# REVISION    STATUS      DESCRIPTION
# 1           superseded  Install complete
# 2           superseded  Upgrade complete
# 3           deployed    Upgrade complete

# Rollback to revision 2
helm rollback my-release 2

# Rollback to previous version
helm rollback my-release

Uninstalling

# Uninstall a release
helm uninstall my-release

# Uninstall but keep history (allows rollback)
helm uninstall my-release --keep-history

Overriding Values

Values can be set three ways (in order of precedence):

# 1. --set flag (highest precedence)
helm install my-release bitnami/nginx \
  --set replicaCount=3 \
  --set service.type=NodePort \
  --set "resources.limits.cpu=500m"

# 2. -f values file
helm install my-release bitnami/nginx -f my-values.yaml

# 3. Default values.yaml in the chart (lowest precedence)

Custom values file example:

# my-values.yaml
replicaCount: 3
service:
  type: NodePort
  port: 80
resources:
  limits:
    cpu: 500m
    memory: 256Mi
  requests:
    cpu: 100m
    memory: 128Mi

Viewing Chart Details

# Show chart info
helm show chart bitnami/nginx

# Show default values (important for knowing what you can override)
helm show values bitnami/nginx

# Show everything
helm show all bitnami/nginx

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Kustomize — Template-Free Customization

Kustomize lets you customize Kubernetes YAML without templates. It uses overlays and patches to modify base configurations.

Built into kubectl since v1.14:

kubectl apply -k <directory>           # Apply kustomized resources
kubectl kustomize <directory>          # Preview the output

Basic Structure

myapp/
├── base/
│   ├── kustomization.yaml
│   ├── deployment.yaml
│   └── service.yaml
└── overlays/
    ├── dev/
    │   └── kustomization.yaml
    └── production/
        ├── kustomization.yaml
        └── increase-replicas.yaml

Base kustomization.yaml

# base/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- deployment.yaml
- service.yaml

# base/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp
spec:
  replicas: 1
  selector:
    matchLabels:
      app: webapp
  template:
    metadata:
      labels:
        app: webapp
    spec:
      containers:
      - name: webapp
        image: nginx:1.25
        ports:
        - containerPort: 80

Dev Overlay

# overlays/dev/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- ../../base                           # Reference the base

namePrefix: dev-                       # Add prefix to all resource names
namespace: development                 # Set namespace for all resources

commonLabels:
  environment: dev                     # Add label to all resources

# Override image
images:
- name: nginx
  newTag: "1.25-alpine"

Production Overlay

# overlays/production/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- ../../base

namePrefix: prod-
namespace: production

commonLabels:
  environment: production

# Patch to increase replicas
patches:
- path: increase-replicas.yaml

images:
- name: nginx
  newTag: "1.25"

# overlays/production/increase-replicas.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp                          # Must match the base resource name
spec:
  replicas: 5

Apply Kustomized Resources

# Preview what will be applied
kubectl kustomize overlays/dev/

# Apply dev overlay
kubectl apply -k overlays/dev/

# Apply production overlay
kubectl apply -k overlays/production/

# Delete
kubectl delete -k overlays/dev/

Common Kustomize Transformations

# kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- deployment.yaml

# Add prefix/suffix to names
namePrefix: staging-
nameSuffix: -v2

# Set namespace
namespace: staging

# Add labels to all resources
commonLabels:
  team: platform

# Add annotations
commonAnnotations:
  managed-by: kustomize

# Override images
images:
- name: nginx
  newName: myregistry.io/nginx
  newTag: "2.0"

# Generate ConfigMaps
configMapGenerator:
- name: app-config
  literals:
  - DB_HOST=mysql
  - LOG_LEVEL=info

# Generate Secrets
secretGenerator:
- name: db-creds
  literals:
  - password=s3cret

Patches — Two Styles

Strategic Merge Patch (merge with the target):

# patches:
# - path: patch.yaml
# In patch.yaml:
apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp
spec:
  replicas: 5
  template:
    spec:
      containers:
      - name: webapp
        resources:
          limits:
            memory: "512Mi"

JSON Patch (precise operations):

patches:
- target:
    kind: Deployment
    name: webapp
  patch: |-
    - op: replace
      path: /spec/replicas
      value: 5
    - op: add
      path: /spec/template/spec/containers/0/resources
      value:
        limits:
          memory: "512Mi"

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Helm vs Kustomize

Feature	Helm	Kustomize
Approach	Templates (Go templating)	Overlays (patch base YAML)
Complexity	Higher (template syntax)	Lower (plain YAML)
Packaging	Charts (distributable)	Directories (must share source)
Versioning	Chart versions + app versions	Git-based
Release management	Yes (install, upgrade, rollback)	No (just kubectl apply)
Dependencies	Chart dependencies	Resource references
Built into kubectl	No (separate binary)	Yes (kubectl -k)
Best for	Third-party apps, complex parameterization	In-house apps, environment overlays

In practice, many teams use both: Helm for third-party charts, Kustomize for in-house applications.

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Exam Tips for Helm & Kustomize

CKA

• Know helm install, helm upgrade, helm rollback, helm uninstall
• Know helm list, helm history, helm get values
• helm.sh/docs is an allowed reference

CKAD

• Know all Helm operations above
• Know kubectl apply -k and kubectl kustomize
• Know how to create a basic kustomization.yaml
• Know how to override images, add labels, set namespace

Quick Reference Commands

# Helm: install something
helm install myapp bitnami/nginx --set replicaCount=3 -n myns --create-namespace

# Helm: upgrade
helm upgrade myapp bitnami/nginx --set replicaCount=5

# Helm: rollback
helm rollback myapp 1

# Helm: check what's installed
helm list -A

# Kustomize: apply
kubectl apply -k ./overlays/production/

# Kustomize: preview
kubectl kustomize ./overlays/production/

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Key Takeaways

1. Helm = package manager with charts, releases, repositories — good for third-party apps
2. helm install, helm upgrade, helm rollback — the three core operations
3. helm get values shows current configuration; --all shows defaults too
4. --dry-run to preview; helm template to render YAML without applying
5. Kustomize = template-free overlays built into kubectl
6. kubectl apply -k applies kustomized resources; kubectl kustomize previews them
7. Kustomize excels at environment overlays (dev/staging/prod from a single base)
8. configMapGenerator and secretGenerator in Kustomize auto-create and hash names
9. Both tools can coexist — use Helm for third-party, Kustomize for in-house