Helm Charts: The Package Manager for Kubernetes

# Install Helm (Linux)
curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash

# macOS
brew install helm

# Windows (choco)
choco install kubernetes-helm

# Verify installation
helm version
helm help

# Add repositories
helm repo add stable https://charts.helm.sh/stable
helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo update

# Search for charts
helm search hub nginx
helm search repo nginx

# Install a chart
helm install my-nginx ingress-nginx/ingress-nginx

# List releases
helm list
helm list --all-namespaces

# Uninstall
helm uninstall my-nginx

# Create a new chart
helm create myapp

# Chart structure:
myapp/
├── Chart.yaml          # Chart metadata
├── values.yaml         # Default values
├── values-dev.yaml     # Dev environment values (custom)
├── values-prod.yaml    # Prod environment values (custom)
├── charts/             # Dependencies
├── templates/          # Kubernetes manifests
│   ├── NOTES.txt       # Help text after install
│   ├── _helpers.tpl    # Template helpers
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── configmap.yaml
│   └── tests/          # Test manifests
└── .helmignore         # Files to ignore

# Examine chart contents
helm show chart myapp/
helm show values myapp/

# Chart.yaml
apiVersion: v2
name: myapp
description: A Helm chart for my Kubernetes application
type: application
version: 0.1.0
appVersion: "1.16.0"

# Dependencies
dependencies:
- name: postgresql
  version: 12.x.x
  repository: https://charts.bitnami.com/bitnami
  condition: postgresql.enabled
- name: redis
  version: 17.x.x
  repository: https://charts.bitnami.com/bitnami
  condition: redis.enabled

# Maintainers
maintainers:
- name: Your Name
  email: your.email@example.com

# Keywords for search
keywords:
- myapp
- web
- backend

# Homepage
home: https://example.com

# Sources
sources:
- https://github.com/example/myapp

# Annotations (for Helm charts repository)
annotations:
  artifacthub.io/license: MIT
  artifacthub.io/operator: "false"

# values.yaml
# Global settings
global:
  environment: production
  imagePullSecrets: []

# Replica count
replicaCount: 2

# Image configuration
image:
  repository: myapp
  pullPolicy: IfNotPresent
  tag: latest

# Image pull secrets
imagePullSecrets: []

# Name override
nameOverride: ""
fullnameOverride: ""

# ServiceAccount
serviceAccount:
  create: true
  annotations: {}
  name: ""

# Pod annotations
podAnnotations: {}

# Pod security context
podSecurityContext: {}
  # fsGroup: 2000

# Container security context
securityContext: {}
  # capabilities:
  #   drop:
  #   - ALL
  # readOnlyRootFilesystem: true
  # runAsNonRoot: true
  # runAsUser: 1000

# Service configuration
service:
  type: ClusterIP
  port: 80
  targetPort: 8080

# Ingress configuration
ingress:
  enabled: false
  className: ""
  annotations: {}
  hosts:
  - host: chart-example.local
    paths:
    - path: /
      pathType: ImplementationSpecific
  tls: []

# Resource limits
resources:
  limits:
    cpu: 500m
    memory: 512Mi
  requests:
    cpu: 250m
    memory: 256Mi

# Autoscaling
autoscaling:
  enabled: false
  minReplicas: 2
  maxReplicas: 10
  targetCPUUtilizationPercentage: 80

# Node selector
nodeSelector: {}

# Tolerations
tolerations: []

# Affinity
affinity: {}

# Environment variables (custom to your app)
env:
  LOG_LEVEL: info
  API_URL: https://api.example.com

# ConfigMap data
configMap:
  enabled: true
  data:
    app.properties: |
      app.name=myapp
      app.version=1.0

# Secret data (base64 encoded)
secret:
  enabled: true
  data:
    api-key: ""  # Will be set via --set or external secrets

# templates/_helpers.tpl - Helper functions
{{- define "myapp.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

{{- define "myapp.fullname" -}}
{{- if .Values.fullnameOverride }}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- $name := default .Chart.Name .Values.nameOverride }}
{{- if contains $name .Release.Name }}
{{- .Release.Name | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }}
{{- end }}
{{- end }}
{{- end }}

{{- define "myapp.labels" -}}
helm.sh/chart: {{ include "myapp.chart" . }}
{{ include "myapp.selectorLabels" . }}
{{- if .Chart.AppVersion }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
{{- end }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

{{- define "myapp.selectorLabels" -}}
app.kubernetes.io/name: {{ include "myapp.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "myapp.fullname" . }}
  labels:
    {{- include "myapp.labels" . | nindent 4 }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      {{- include "myapp.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      labels:
        {{- include "myapp.selectorLabels" . | nindent 8 }}
    spec:
      containers:
      - name: {{ .Chart.Name }}
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
        imagePullPolicy: {{ .Values.image.pullPolicy }}
        ports:
        - containerPort: {{ .Values.service.targetPort }}
          name: http
        env:
        {{- range $key, $value := .Values.env }}
        - name: {{ $key }}
          value: {{ $value | quote }}
        {{- end }}
        resources:
          {{- toYaml .Values.resources | nindent 10 }}
      {{- with .Values.nodeSelector }}
      nodeSelector:
        {{- toYaml . | nindent 8 }}
      {{- end }}

# values-dev.yaml
replicaCount: 1

image:
  tag: dev-latest

service:
  type: ClusterIP

ingress:
  enabled: false

env:
  LOG_LEVEL: debug
  API_URL: https://dev-api.example.com

resources:
  limits:
    cpu: 200m
    memory: 256Mi
  requests:
    cpu: 100m
    memory: 128Mi

autoscaling:
  enabled: false

# values-staging.yaml
replicaCount: 2

image:
  tag: staging-latest

service:
  type: ClusterIP

ingress:
  enabled: true
  host: staging.example.com

env:
  LOG_LEVEL: info
  API_URL: https://staging-api.example.com

resources:
  limits:
    cpu: 500m
    memory: 512Mi
  requests:
    cpu: 250m
    memory: 256Mi

# values-prod.yaml
replicaCount: 5

image:
  tag: latest

service:
  type: LoadBalancer

ingress:
  enabled: true
  host: example.com
  tls:
  - hosts:
    - example.com
    secretName: tls-secret

env:
  LOG_LEVEL: warn
  API_URL: https://api.example.com

resources:
  limits:
    cpu: 1000m
    memory: 1Gi
  requests:
    cpu: 500m
    memory: 512Mi

autoscaling:
  enabled: true
  minReplicas: 3
  maxReplicas: 10
  targetCPUUtilizationPercentage: 70

# Create chart
helm create myapp-chart
cd myapp-chart

# Customize templates
# Edit templates/deployment.yaml, service.yaml, etc.

# Create environment values
cat > values-dev.yaml << 'EOF'
environment: dev
replicaCount: 1
ingress:
  enabled: false
EOF

cat > values-staging.yaml << 'EOF'
environment: staging
replicaCount: 2
ingress:
  enabled: true
  host: staging.myapp.com
EOF

cat > values-prod.yaml << 'EOF'
environment: production
replicaCount: 5
ingress:
  enabled: true
  host: myapp.com
  tls:
  - secretName: myapp-tls
    hosts:
    - myapp.com
autoscaling:
  enabled: true
  minReplicas: 3
  maxReplicas: 10
EOF

# Lint chart
helm lint .

# Template rendering (dry-run)
helm template myapp .

# Install with different environments
helm install myapp-dev . -f values-dev.yaml --namespace dev --create-namespace
helm install myapp-staging . -f values-staging.yaml --namespace staging --create-namespace
helm install myapp-prod . -f values-prod.yaml --namespace prod --create-namespace

# Override values on command line
helm install myapp . --set replicaCount=3 --set image.tag=v1.2.3

# Upgrade release
helm upgrade myapp-staging . -f values-staging.yaml --set image.tag=v1.2.4

# Rollback
helm rollback myapp-prod 2

# List releases
helm list -A

# Get release manifest
helm get manifest myapp-prod

# Get release values
helm get values myapp-prod

# Uninstall
helm uninstall myapp-dev -n dev

# Chart.yaml with dependencies
apiVersion: v2
name: myapp-with-deps
dependencies:
- name: postgresql
  version: "12.x.x"
  repository: "https://charts.bitnami.com/bitnami"
  condition: postgresql.enabled
- name: redis
  version: "17.x.x"
  repository: "https://charts.bitnami.com/bitnami"
  condition: redis.enabled
- name: prometheus
  version: "23.x.x"
  repository: "https://prometheus-community.github.io/helm-charts"
  condition: monitoring.enabled
- name: grafana
  version: "6.x.x"
  repository: "https://grafana.github.io/helm-charts"
  condition: monitoring.enabled

# Update dependencies
helm dependency update

# List dependencies
helm dependency list

# Build dependencies directory
helm dependency build

# values.yaml for dependencies
postgresql:
  enabled: true
  auth:
    postgresPassword: "secret"
    database: myapp
  primary:
    persistence:
      size: 10Gi

redis:
  enabled: true
  architecture: standalone
  auth:
    password: "redis-secret"

monitoring:
  enabled: false

prometheus:
  server:
    persistentVolume:
      size: 50Gi

grafana:
  adminPassword: admin

# Package chart
helm package myapp-chart
# Creates: myapp-chart-0.1.0.tgz

# Push to repository (OCI registry)
helm registry login registry.example.com
helm push myapp-chart-0.1.0.tgz oci://registry.example.com/helm

# Or use ChartMuseum (open-source Helm repo)
docker run -d -p 8080:8080 -e STORAGE=local -e STORAGE_LOCAL_ROOT=/charts chartmuseum/chartmuseum

# Push to ChartMuseum
curl --data-binary "@myapp-chart-0.1.0.tgz" http://localhost:8080/api/charts

# Add repository
helm repo add myrepo http://localhost:8080
helm repo update

# Install from repository
helm install myapp myrepo/myapp-chart

# Create GitHub Pages Helm repo
# 1. Create gh-pages branch
# 2. Place charts in repository
# 3. Generate index.yaml
helm repo index . --url https://username.github.io/repo

# Then add
helm repo add myrepo https://username.github.io/repo