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Helm Cheatsheet

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1. Introduction:

  • Helm is a package manager for Kubernetes, helping you define, install, and upgrade even the most complex Kubernetes applications. It uses charts to package Kubernetes resources.

2. Key Concepts:

  • Chart: A collection of files that describe a set of Kubernetes resources.
  • Release: An instance of a chart running in a Kubernetes cluster.
  • Repository: A place where charts can be collected and shared.

3. Installing Helm:

  • Helm Installation:

    curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash

  • Add a Helm Repository:

    helm repo add stable https://charts.helm.sh/stable
helm repo update

4. Helm Commands:

  • Install a Chart:

    helm install my-release stable/nginx

  • List Releases:

    helm list

  • Upgrade a Release:

    helm upgrade my-release stable/nginx

  • Uninstall a Release:

    helm uninstall my-release

  • Search for Charts:

    helm search repo nginx

5. Chart Structure:

  • Basic Chart Structure:

    my-chart/
├── Chart.yaml
├── values.yaml
├── charts/
├── templates/
│   ├── deployment.yaml
│   ├── service.yaml
│   └── _helpers.tpl

  • Chart.yaml:

    apiVersion: v2
name: my-chart
description: A Helm chart for Kubernetes
version: 0.1.0

  • values.yaml:

    replicaCount: 3
image:
  repository: nginx
  tag: stable

  • Template Example (deployment.yaml):

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

6. Helm Lifecycle:

  • Creating a New Chart:

    helm create my-chart

  • Templating:

    • List all template values:

      helm template my-release my-chart

    • Lint a Chart:

      helm lint my-chart

7. Helm Repositories:

  • Creating a Local Helm Repository:

    helm repo index ./charts --url http://example.com/charts

  • Serving Charts:

    helm serve --address 0.0.0.0:8879

8. Helm Hooks:

  • Example of a Pre-Install Hook:

    apiVersion: batch/v1
kind: Job
metadata:
  name: "{{ .Release.Name }}-preinstall"
  annotations:
    "helm.sh/hook": pre-install
spec:
  template:
    spec:
      containers:
      - name: preinstall
        image: busybox
        command: ['sh', '-c', 'echo Hello Helm']
      restartPolicy: Never

9. Helm and CI/CD:

  • Using Helm in Jenkins Pipeline:

    pipeline {
  agent any
  stages {
    stage('Deploy') {
      steps {
        script {
          sh "helm upgrade --install my-release ./my-chart"
        }
      }
    }
  }
}

10. Advanced Helm Concepts:

  • Subcharts: Use subcharts to package related Kubernetes resources together.
  • Chart Museum: Helm repository server to store and manage Helm charts.
  • Helmfile: A declarative spec for deploying Helm charts.

11. Helm Security:

  • Chart Signing:

    • Sign and verify Helm charts to ensure integrity.
    helm package --sign --key <key> --keyring <keyring> my-chart
helm verify my-chart-0.1.0.tgz

  • RBAC: Control access to Helm releases with Kubernetes RBAC.

12. Troubleshooting Helm:

  • Debugging a Chart Installation:

    helm install --debug --dry-run my-release ./my-chart

  • Checking Helm Release History:

    helm history my-release

  • Rollback a Release:

    helm rollback my-release 1