Skip to main content

Helm

You want to deploy the same application to three environments: dev, staging, production. The YAML is 90% identical. The image tag, replica count, resource limits, and ingress hostname differ.

You have two bad options: copy the YAML three times (now you have three copies to maintain) or write a shell script that patches the YAML (now you have a fragile script to maintain).

So you use Helm. Helm packages Kubernetes resources into charts — templates with configurable values. Deploy with different values for different environments. One chart, three deployments.

The chart structure​

my-chart/
├── Chart.yaml          ← chart metadata (name, version, description)
├── values.yaml         ← default configuration values
└── templates/          ← Kubernetes manifests with Go template syntax
    ├── deployment.yaml
    ├── service.yaml
    └── ingress.yaml

Chart.yaml defines the chart:

apiVersion: v2
name: my-app
description: A simple web application
version: 1.0.0
appVersion: "2.3.1"

values.yaml defines the defaults:

replicaCount: 1
image:
  repository: my-org/my-app
  tag: "2.3.1"
  pullPolicy: IfNotPresent
service:
  type: ClusterIP
  port: 80
resources:
  limits:
    memory: 256Mi
    cpu: 200m

A template uses Go template syntax to inject values:

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}-app
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    spec:
      containers:
      - name: app
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
        resources:
          limits:
            memory: {{ .Values.resources.limits.memory }}
            cpu: {{ .Values.resources.limits.cpu }}

Releases​

When you deploy a chart with Helm, you create a release. A release is an instance of a chart running in the cluster with a specific set of values.

You can have multiple releases of the same chart. helm install prod my-chart and helm install staging my-chart are two independent releases.

Hands-on​

Lab files

Fork eigenbytes-devops-labs — a complete chart is ready in 05-platform-engineering/helm/my-app/. Skip the helm create step and deploy directly.

Create a chart​

helm create my-app
ls my-app/
# Chart.yaml  charts/  templates/  values.yaml

Helm scaffolds a complete chart with example templates. Review the structure, then deploy it.

Deploy to local Kubernetes​

# Install the chart with default values
helm install my-release my-app/

# Check what was deployed
helm list
kubectl get all -l app.kubernetes.io/instance=my-release

# See what Helm would apply (dry run)
helm install my-release my-app/ --dry-run --debug | head -60

Override values for a different environment​

# Create a values file for production
cat > values-prod.yaml << 'EOF'
replicaCount: 3
image:
  tag: "2.3.1"
resources:
  limits:
    memory: 512Mi
    cpu: 500m
EOF

# Deploy production with overrides
helm install prod my-app/ -f values-prod.yaml

# Or override inline
helm install staging my-app/ \
  --set replicaCount=2 \
  --set image.tag=2.2.0

Upgrade and rollback​

# Upgrade to a new image
helm upgrade my-release my-app/ --set image.tag=2.4.0

# View history
helm history my-release

# Rollback to previous version
helm rollback my-release

# Rollback to specific revision
helm rollback my-release 2

Use a chart from a repository​

# Add the ingress-nginx chart repository
helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm repo update

# Search for charts
helm search repo nginx

# Install
helm install ingress-nginx ingress-nginx/ingress-nginx \
  --namespace ingress-nginx \
  --create-namespace

# Check values for a chart
helm show values ingress-nginx/ingress-nginx | head -30

Cleanup​

helm uninstall my-release staging prod --ignore-not-found
helm uninstall ingress-nginx -n ingress-nginx --ignore-not-found

Quick reference​

helm create <name>                           # scaffold a chart
helm install <release> <chart>               # deploy
helm install <release> <chart> -f values.yaml  # with values file
helm upgrade <release> <chart>               # update
helm rollback <release>                      # rollback
helm uninstall <release>                     # delete
helm list                                    # list releases
helm history <release>                       # deployment history
helm repo add <name> <url>                   # add chart repo
helm repo update                             # refresh repos
helm search repo <term>                      # find charts
helm show values <chart>                     # show default values
helm template <release> <chart>             # render templates without deploying
helm diff upgrade <release> <chart>         # show what would change (plugin)

Lab files: eigenbytes-devops-labs/05-platform-engineering/helm