Create Kubernetes - Helm.md

Author: scaler-aayush

DevOps Tools 1 Module/Kubernetes - Helm.md

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+# Kubernetes - Helm Notes
+
+
+## **What is Helm?**
+Helm is a package manager for Kubernetes that simplifies the deployment, management, and scaling of applications. It uses preconfigured templates, called Helm Charts, to automate the process of creating Kubernetes resources.
+
+### **Why Use Helm?**
+- **Simplifies Kubernetes deployments**: Automates the creation and management of Kubernetes resources.
+- **Provides version control**: Manage different versions of your application.
+- **Reusable templates**: Create consistent and repeatable deployments.
+
+---
+
+## **Key Concepts in Helm**
+
+### **1. Helm Charts**
+Helm Charts are collections of templates that define Kubernetes resources. These charts contain all the necessary files to deploy an application on Kubernetes.
+
+#### **Structure of a Helm Chart**
+- **Chart.yaml**: Contains metadata about the chart (name, version, description).
+- **Values.yaml**: Contains default configuration values for the chart.
+- **Templates/**: Directory containing YAML templates for Kubernetes resources.
+
+#### **Example of Chart.yaml:**
+```yaml
+apiVersion: v2
+name: my-application
+version: 1.0.0
+description: A Helm chart for my application
+```
+
+### **2. Helm Repositories**
+Helm Repositories are storage locations for Helm Charts. These repositories can be public or private and allow you to store and retrieve charts for your deployments.
+
+#### **Popular Helm Repositories:**
+- Bitnami
+- ArtifactHub
+- Helm Stable Repository
+
+### **3. Helm Releases**
+A Helm Release is a specific deployment of a Helm Chart. Every time a chart is deployed, it is tracked as a release.
+
+---
+
+## **Key Features of Helm**
+
+| **Feature**           | **Description**                                 |
+|-----------------------|-------------------------------------------------|
+| Simplified Deployment | Automates Kubernetes resource creation          |
+| Version Control       | Tracks application versions and rollbacks       |
+| Reusable Templates    | Creates consistent configurations using charts  |
+| Scalability           | Easily manage application scaling               |
+
+---
+
+## **Helm Workflow**
+The typical workflow for using Helm involves creating charts, installing releases, upgrading them, and rolling back if necessary.
+
+### **Step 1: Create a Chart**
+```bash
+helm create my-chart
+```
+This command generates a basic chart structure with the necessary files.
+
+### **Step 2: Install a Release**
+```bash
+helm install <release-name> <chart>
+```
+This command installs a release from the specified chart.
+
+#### **Example:**
+```bash
+helm install my-app ./my-chart
+```
+
+### **Step 3: Upgrade a Release**
+```bash
+helm upgrade <release-name> <chart>
+```
+This command upgrades an existing release with new chart configurations.
+
+#### **Example:**
+```bash
+helm upgrade my-app ./my-chart
+```
+
+### **Step 4: Rollback a Release**
+```bash
+helm rollback <release-name> <revision>
+```
+This command rolls back a release to a previous revision.
+
+#### **Example:**
+```bash
+helm rollback my-app 1
+```
+
+---
+
+## **File Descriptions in Helm**
+
+### **1. Chart.yaml**
+This file contains metadata about the Helm Chart.
+
+#### **Example:**
+```yaml
+apiVersion: v2
+name: my-chart
+version: 1.0.0
+description: A sample Helm chart
+```
+
+### **2. Values.yaml**
+Contains the default configuration values for the chart.
+
+#### **Example:**
+```yaml
+replicaCount: 2
+image:
+  repository: nginx
+  tag: latest
+  pullPolicy: IfNotPresent
+service:
+  type: ClusterIP
+  port: 80
+```
+
+### **3. Templates/**
+Contains Kubernetes resource templates.
+
+#### **Example Template:** ConfigMap
+```yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: {{ .Release.Name }}-configmap
+data:
+  myValue: "Example"
+```
+
+---
+
+## **Pre-existing Helm Charts**
+There are several pre-existing Helm Charts available in repositories:
+
+| **Chart**       | **Description**                      |
+|-----------------|--------------------------------------|
+| Nginx           | Web server                           |
+| Prometheus      | Monitoring system                    |
+| Grafana         | Dashboard and visualization tool     |
+| Jenkins         | Continuous Integration server        |
+| MySQL           | Database server                      |
+
+---
+
+## **Helm Commands**
+
+| **Command**                          | **Description**                               |
+|--------------------------------------|-----------------------------------------------|
+| `helm install <release> <chart>`     | Install a Helm chart                          |
+| `helm upgrade <release> <chart>`     | Upgrade an existing release                  |
+| `helm rollback <release> <revision>` | Rollback a release to a previous revision     |
+| `helm package <path-to-chart>`       | Package a chart into a `.tgz` archive         |
+| `helm push <chart>`                  | Push a chart to a repository                 |
+
+---
+
+## **Helm Templates**
+Helm templates use Go template syntax to create dynamic configurations.
+
+### **1. Helper Templates**
+Helper templates are reusable components defined in a `_helpers.tpl` file.
+
+#### **Example:**
+```yaml
+{{- define "my-chart.fullname" -}}
+{{ .Release.Name }}-{{ .Chart.Name }}
+{{- end -}}
+```
+
+### **2. Dynamic Names in Templates**
+Dynamic names use variables to customize resource names.
+
+#### **Examples:**
+```yaml
+metadata:
+  name: {{ .Release.Name }}-configmap
+```
+```yaml
+metadata:
+  name: {{ .Release.Name | lower }}-deployment
+```
+
+### **3. Conditional Rendering**
+Conditional rendering allows templates to include or exclude configurations based on values.
+
+#### **Example:**
+```yaml
+selector:
+  app: my-app
+{{- if .Values.service.external }}
+externalIPs:
+  - {{ .Values.service.external }}
+{{- end }}
+```
+
+---
+
+## **Deployment Example: Nginx**
+
+1. **Install Nginx using Helm:**
+```bash
+helm install my-nginx bitnami/nginx
+```
+
+2. **Customize using values.yaml:**
+```yaml
+replicaCount: 2
+service:
+  type: LoadBalancer
+```
+
+---
+
+## **Deployment Example: Prometheus and Grafana**
+Use existing Helm charts to set up monitoring tools.
+
+1. **Install Prometheus:**
+```bash
+helm install prometheus prometheus-community/prometheus
+```
+
+2. **Install Grafana:**
+```bash
+helm install grafana grafana/grafana
+```
+
+---
+
+## **Summary**
+Helm simplifies Kubernetes application deployments by providing reusable charts, version control, and dynamic templates. It reduces the complexity of managing Kubernetes resources and ensures consistent configurations across environments.