Helm Basics
Helm Basics
What is Helm?
Helm is the package manager for Kubernetes. It simplifies defining, installing, and upgrading Kubernetes applications.
Chart: Package of Kubernetes manifests
Release: Running instance of a chart
Repository: Collection of charts
Values: Configuration passed to templates
Helm Commands
# Install Helm
curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash
# Add repository
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update
# Search charts
helm search repo nginx
helm search hub prometheus
# Install chart
helm install my-release bitnami/nginx
helm install my-release bitnami/nginx -n production --create-namespace
# Install with values
helm install my-release bitnami/nginx -f values.yaml
helm install my-release bitnami/nginx --set replicaCount=3 --set service.type=ClusterIP
# Upgrade release
helm upgrade my-release bitnami/nginx -f values.yaml
helm upgrade --install my-release bitnami/nginx # Install or upgrade
# Rollback
helm rollback my-release 1 # Rollback to revision 1
# Uninstall
helm uninstall my-release
# List releases
helm list -A
helm list -n production
# Release history
helm history my-release
# Show chart info
helm show chart bitnami/nginx
helm show values bitnami/nginx
helm show readme bitnami/nginx
# Lint chart
helm lint ./mychart
# Package chart
helm package ./mychart
# Template rendering (debug)
helm template my-release ./mychart -f values.yaml
Creating Charts
Creating Charts
Chart Structure
# Create a new chart
helm create mychart
# Structure:
mychart/
├── Chart.yaml # Chart metadata
├── values.yaml # Default values
├── charts/ # Dependency charts
├── templates/ # Template files
│ ├── deployment.yaml
│ ├── service.yaml
│ ├── ingress.yaml
│ ├── hpa.yaml
│ ├── serviceaccount.yaml
│ ├── _helpers.tpl # Template helpers
│ └── tests/
│ └── test-connection.yaml
├── .helmignore
└── README.md
Chart.yaml
apiVersion: v2
name: myapp
description: My application Helm chart
type: application
version: 0.1.0 # Chart version
appVersion: "1.0.0" # Application version
keywords:
- web
- api
maintainers:
- name: John Doe
email: john@example.com
dependencies:
- name: postgresql
version: "12.x.x"
repository: "https://charts.bitnami.com/bitnami"
condition: postgresql.enabled
values.yaml
replicaCount: 2
image:
repository: myapp
pullPolicy: IfNotPresent
tag: ""
service:
type: ClusterIP
port: 80
targetPort: 8080
ingress:
enabled: true
className: nginx
hosts:
- host: api.example.com
paths:
- path: /
pathType: Prefix
tls:
- secretName: api-tls
hosts:
- api.example.com
resources:
requests:
memory: 256Mi
cpu: 250m
limits:
memory: 512Mi
cpu: 1000m
autoscaling:
enabled: true
minReplicas: 2
maxReplicas: 10
targetCPUUtilizationPercentage: 70
postgresql:
enabled: true
auth:
database: myapp
username: myapp
Template Files
# 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 }}
{{- if .Values.resources }}
resources:
{{- toYaml .Values.resources | nindent 10 }}
{{- end }}
# templates/service.yaml
apiVersion: v1
kind: Service
metadata:
name: {{ include "myapp.fullname" . }}
spec:
type: {{ .Values.service.type }}
ports:
- port: {{ .Values.service.port }}
targetPort: {{ .Values.service.targetPort }}
selector:
{{- include "myapp.selectorLabels" . | nindent 4 }}
# templates/_helpers.tpl
{{- define "myapp.fullname" -}}
{{- if .Values.fullnameOverride }}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- .Release.Name | trunc 63 | trimSuffix "-" }}
{{- end }}
{{- end }}
{{- define "myapp.labels" -}}
helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version }}
app.kubernetes.io/name: {{ .Chart.Name }}
app.kubernetes.io/instance: {{ .Release.Name }}
app.kubernetes.io/version: {{ .Chart.AppVersion }}
{{- end }}
{{- define "myapp.selectorLabels" -}}
app.kubernetes.io/name: {{ .Chart.Name }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}
Helm Hooks and Conditions
Helm Hooks and Conditions
Helm Hooks
# Pre-install hook (runs before install)
apiVersion: batch/v1
kind: Job
metadata:
name: {{ include "myapp.fullname" . }}-db-migrate
annotations:
"helm.sh/hook": pre-install,pre-upgrade
"helm.sh/hook-weight": "0" # Execution order
"helm.sh/hook-delete-policy": before-hook-creation
spec:
template:
spec:
containers:
- name: migrate
image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
command: ["./migrate.sh"]
restartPolicy: Never
backoffLimit: 1
# Post-install hook
apiVersion: v1
kind: Pod
metadata:
name: {{ include "myapp.fullname" . }}-verify
annotations:
"helm.sh/hook": post-install,post-upgrade
"helm.sh/hook-delete-policy": hook-succeeded
spec:
containers:
- name: verify
image: curlimages/curl
command: ['curl', '-f', 'http://{{ include "myapp.fullname" . }}:{{ .Values.service.port }}/health']
restartPolicy: Never
# Hook weights (lower runs first)
# hook-weight: "-1" runs before "0" runs before "1"
# Hook delete policies:
# before-hook-creation - Delete previous hook before creating new one
# hook-succeeded - Delete hook after successful completion
# hook-failed - Delete hook after failure
Conditions
# templates/ingress.yaml (only create if ingress.enabled)
{{- if .Values.ingress.enabled -}}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: {{ include "myapp.fullname" . }}
spec:
{{- if .Values.ingress.className }}
ingressClassName: {{ .Values.ingress.className }}
{{- end }}
{{- if .Values.ingress.tls }}
tls:
{{- range .Values.ingress.tls }}
- hosts:
{{- range .hosts }}
- {{ . | quote }}
{{- end }}
secretName: {{ .secretName }}
{{- end }}
{{- end }}
rules:
{{- range .Values.ingress.hosts }}
- host: {{ .host | quote }}
http:
paths:
{{- range .paths }}
- path: {{ .path }}
pathType: {{ .pathType }}
backend:
service:
name: {{ include "myapp.fullname" $ }}
port:
number: {{ $.Values.service.port }}
{{- end }}
{{- end }}
{{- end }}
# templates/hpa.yaml
{{- if .Values.autoscaling.enabled }}
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
spec:
minReplicas: {{ .Values.autoscaling.minReplicas }}
maxReplicas: {{ .Values.autoscaling.maxReplicas }}
metrics:
- type: Resource
resource:
name: cpu
target:
type: Utilization
averageUtilization: {{ .Values.autoscaling.targetCPUUtilizationPercentage }}
{{- end }}