14 — Helm

What is Helm?

Package manager for Kubernetes — bundle K8s manifests into reusable, configurable charts.

apt install nginx       → installs package on Linux
helm install nginx      → installs app on Kubernetes

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Key Concepts

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Essential Commands

# Add repositories
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update

# Search
helm search repo nginx
helm search hub postgres          # Search Artifact Hub

# Install
helm install my-release bitnami/nginx
helm install my-db bitnami/postgresql -f values.yaml
helm install my-db bitnami/postgresql --set auth.postgresPassword=secret

# List releases
helm list
helm list -A                      # All namespaces

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

# Rollback
helm rollout history my-release
helm rollback my-release 1        # Rollback to revision 1

# Uninstall
helm uninstall my-release

# Debug
helm template my-release bitnami/nginx -f values.yaml   # Render templates
helm install --dry-run --debug my-release ./my-chart     # Dry run

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Chart Structure

my-chart/
├── Chart.yaml          # Chart metadata (name, version, dependencies)
├── values.yaml         # Default configuration values
├── templates/
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── configmap.yaml
│   ├── _helpers.tpl    # Template helpers
│   └── NOTES.txt       # Post-install message
└── charts/             # Dependencies (sub-charts)

Chart.yaml

apiVersion: v2
name: my-app
description: My application Helm chart
version: 1.0.0          # Chart version
appVersion: "2.0.0"     # App version
dependencies:
  - name: postgresql
    version: 12.x.x
    repository: https://charts.bitnami.com/bitnami

values.yaml

replicaCount: 3

image:
  repository: my-app
  tag: "1.0.0"
  pullPolicy: IfNotPresent

service:
  type: ClusterIP
  port: 80

ingress:
  enabled: true
  host: myapp.com

resources:
  requests:
    memory: "128Mi"
    cpu: "250m"
  limits:
    memory: "512Mi"
    cpu: "1"

env:
  NODE_ENV: production

Template Example

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "my-chart.fullname" . }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ include "my-chart.name" . }}
  template:
    metadata:
      labels:
        app: {{ include "my-chart.name" . }}
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          ports:
            - containerPort: {{ .Values.service.port }}
          resources:
            {{- toYaml .Values.resources | nindent 12 }}
          env:
            {{- range $key, $value := .Values.env }}
            - name: {{ $key }}
              value: {{ $value | quote }}
            {{- end }}

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Overriding Values

# File (recommended)
helm install my-app ./my-chart -f production-values.yaml

# Command line
helm install my-app ./my-chart --set replicaCount=5 --set image.tag=2.0.0

# Multiple files (later files override earlier)
helm install my-app ./my-chart -f values.yaml -f production.yaml

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Common Helm Charts

# PostgreSQL
helm install db bitnami/postgresql --set auth.postgresPassword=secret

# Redis
helm install cache bitnami/redis

# Nginx Ingress Controller
helm install ingress-nginx ingress-nginx/ingress-nginx

# Prometheus + Grafana
helm install monitoring prometheus-community/kube-prometheus-stack

# Cert-Manager (TLS certificates)
helm install cert-manager jetstack/cert-manager --set installCRDs=true

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Key Takeaways

• Helm = package manager for K8s — install complex apps with one command
• Charts bundle K8s manifests; values.yaml configures them
• Use helm install -f values.yaml for environment-specific config
• Use helm template to preview rendered manifests before installing
• Use helm rollback for easy rollbacks
• Bitnami and Artifact Hub have charts for most popular software