Using Helm in Kubernetes

helm version

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

# List repositories
helm repo list

# Update repositories (sync latest chart info)
helm repo update

# Remove repository
helm repo remove bitnami

# Search charts in repository
helm search repo nginx

# Search in Artifact Hub
helm search hub nginx

# View chart information
helm show chart bitnami/nginx
helm show values bitnami/nginx
helm show readme bitnami/nginx

# Install chart
helm install my-nginx bitnami/nginx

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

# Specify values from command line
helm install my-nginx bitnami/nginx --set service.type=LoadBalancer

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

# Upgrade (install if not exists)
helm upgrade --install my-nginx bitnami/nginx

# Rollback
helm rollback my-nginx 1

# Uninstall
helm uninstall my-nginx

apiVersion: v2           # Helm 3 uses v2
name: mychart
version: 1.0.0           # Chart version (SemVer)
appVersion: "1.16.0"     # Application version
description: My application Helm chart
type: application        # application or library
keywords:
  - web
  - nginx
maintainers:
  - name: DevOps Team
    email: [email protected]
dependencies:
  - name: redis
    version: "17.x.x"
    repository: "https://charts.bitnami.com/bitnami"
    condition: redis.enabled

replicaCount: 1

image:
  repository: nginx
  tag: "1.21"
  pullPolicy: IfNotPresent

service:
  type: ClusterIP
  port: 80

resources:
  limits:
    cpu: 100m
    memory: 128Mi
  requests:
    cpu: 50m
    memory: 64Mi

nodeSelector: {}
tolerations: []
affinity: {}

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}-{{ .Chart.Name }}
  labels:
    app: {{ .Chart.Name }}
    release: {{ .Release.Name }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ .Chart.Name }}
  template:
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          ports:
            - containerPort: {{ .Values.service.port }}

# Conditional
{{- if .Values.ingress.enabled }}
apiVersion: networking.k8s.io/v1
kind: Ingress
...
{{- end }}

# Loop
{{- range .Values.extraEnvVars }}
- name: {{ .name }}
  value: {{ .value | quote }}
{{- end }}

# with (scope change)
{{- with .Values.nodeSelector }}
nodeSelector:
  {{- toYaml . | nindent 2 }}
{{- end }}

{{/* Common labels definition */}}
{{- define "mychart.labels" -}}
helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version }}
app.kubernetes.io/name: {{ .Chart.Name }}
app.kubernetes.io/instance: {{ .Release.Name }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

{{/* Usage */}}
metadata:
  labels:
    {{- include "mychart.labels" . | nindent 4 }}

# Create new chart
helm create mychart

# Lint chart
helm lint mychart

# Render templates (without installing)
helm template my-release mychart

# Render with specific values
helm template my-release mychart -f prod-values.yaml

# Dry run (API server validation)
helm install my-release mychart --dry-run --debug

# Package chart
helm package mychart

# Update dependencies
helm dependency update mychart

apiVersion: batch/v1
kind: Job
metadata:
  name: "{{ .Release.Name }}-db-migrate"
  annotations:
    "helm.sh/hook": pre-upgrade
    "helm.sh/hook-weight": "5"
    "helm.sh/hook-delete-policy": hook-succeeded
spec:
  template:
    spec:
      containers:
        - name: migrate
          image: myapp:{{ .Values.image.tag }}
          command: ["./migrate.sh"]
      restartPolicy: Never

stages:
  - lint
  - test
  - deploy

lint:
  stage: lint
  script:
    - helm lint ./charts/myapp

test:
  stage: test
  script:
    - helm template myapp ./charts/myapp
    - helm install myapp ./charts/myapp --dry-run --debug

deploy:
  stage: deploy
  script:
    - helm upgrade --install myapp ./charts/myapp
      --namespace production
      --create-namespace
      -f values-prod.yaml
      --wait
      --timeout 5m
  only:
    - main