Welcome to Day 3 of the Azure Zero to Hero series!
Today’s focus is on Infrastructure as Code (IaC) in Azure using ARM Templates.

You’ll learn:

What is IaC?
Why ARM Templates matter in Azure
The structure of an ARM template
How to deploy one from the CLI
Real-world use case with a simple example

🧠 What is Infrastructure as Code (IaC)?

Infrastructure as Code (IaC) is the practice of defining your cloud infrastructure using code or configuration files, rather than clicking through GUIs.

With IaC, you can:

Automate deployments
Version control your infrastructure
Reuse templates
Ensure consistency across environments (Dev → Test → Prod)

💬 ARM Template: What and Why?

ARM = Azure Resource Manager
ARM Templates are JSON files that define the infrastructure and configuration for your Azure solution.

Think of it as a blueprint — define once, deploy many times.

✅ Benefits:

Declarative syntax
Repeatable deployments
Supports complex dependency management
Native Azure support
Integrates with Azure DevOps, GitHub Actions, etc.

📐 ARM Template Structure

Here’s what a basic ARM template looks like:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "vmName": {
      "type": "string",
      "defaultValue": "myarmvm"
    }
  },
  "resources": [
    {
      "type": "Microsoft.Compute/virtualMachines",
      "apiVersion": "2022-11-01",
      "name": "[parameters('vmName')]",
      "location": "[resourceGroup().location]",
      "properties": {
        "hardwareProfile": {
          "vmSize": "Standard_B1s"
        },
        ...
      }
    }
  ]
}

🧪 Step-by-Step: Deploy an ARM Template

📁 1. Create a simple ARM template

Save the below file as vm-template.json:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "vmName": {
      "type": "string",
      "defaultValue": "vmfromtemplate"
    },
    "adminUsername": {
      "type": "string"
    },
    "adminPassword": {
      "type": "securestring"
    }
  },
  "resources": [
    {
      "type": "Microsoft.Compute/virtualMachines",
      "apiVersion": "2022-11-01",
      "name": "[parameters('vmName')]",
      "location": "[resourceGroup().location]",
      "properties": {
        "hardwareProfile": {
          "vmSize": "Standard_B1s"
        },
        "osProfile": {
          "computerName": "[parameters('vmName')]",
          "adminUsername": "[parameters('adminUsername')]",
          "adminPassword": "[parameters('adminPassword')]"
        },
        "storageProfile": {
          "imageReference": {
            "publisher": "Canonical",
            "offer": "UbuntuServer",
            "sku": "20_04-lts",
            "version": "latest"
          },
          "osDisk": {
            "createOption": "FromImage"
          }
        },
        "networkProfile": {
          "networkInterfaces": [
            {
              "id": "[resourceId('Microsoft.Network/networkInterfaces', concat(parameters('vmName'),'-nic'))]"
            }
          ]
        }
      }
    }
  ]
}

🧪 2. Deploy the template using Azure CLI

Create a resource group:

az group create --name arm-demo-rg --location eastus

Deploy the template:

az deployment group create \
  --name vm-deployment \
  --resource-group arm-demo-rg \
  --template-file vm-template.json \
  --parameters adminUsername=azureuser adminPassword=MyP@ssw0rd123

✅ Your VM and all supporting resources will be created as defined in the JSON template.

🧾 Best Practices with ARM Templates

Practice	Why it Matters
Use parameter files	To separate configuration from code
Use linked templates	For modularization and reusability
Store templates in source control	Enables versioning and collaboration
Validate templates before deployment	Catch issues early

🧠 ARM vs Bicep vs Terraform (Quick Comparison)

Feature	ARM Template	Bicep	Terraform
Language	JSON	Bicep (DSL)	HCL (HashiCorp)
Complexity	High (verbose)	Low (simplified)	Medium
Native to Azure	✅	✅	❌ (uses provider)
Reusability	Manual effort	✅	✅

👉 We’ll explore Bicep in a future post for cleaner, ARM-compatible IaC.

✅ Summary

Step	Task
1️⃣	Learned what ARM templates are
2️⃣	Created a JSON template
3️⃣	Deployed it using Azure CLI
4️⃣	Understood ARM vs Bicep vs Terraform

🔜 Coming Up: Day 4 – Using Azure Bicep: The Future of ARM Templates

We’ll learn how Bicep simplifies ARM deployments with a cleaner syntax, modular structure, and developer-friendly tooling.

💬 Need help writing your own ARM templates? Drop a question in the comments!
📌 Follow for more updates in the Azure Zero to Hero journey.

📦 Day 3: Understanding ARM Templates & Infrastructure as Code (IaC)