Adding VM Instance View Details, e.g. osName, to the VM Resource Object JSON (for Custom Policy Use)

Try below:

Step 1: Retrieve VM Instance View Data

You can use Azure CLI or PowerShell to retrieve the VM instance view data, which includes the operating system information.

Using Azure CLI:

az vm get-instance-view --resource-group <ResourceGroupName> --name <VMName> --query instanceView

Using PowerShell:

Get-AzVM -ResourceGroupName <ResourceGroupName> -Name <VMName> -Status

Step 2: Add Custom Tags or Metadata

You can add custom tags or metadata to your VM resource object to include the operating system information. This can be done using Azure CLI, PowerShell, or directly in the ARM template.

Using Azure CLI:

az vm update --resource-group <ResourceGroupName> --name <VMName> --set tags.osName=<OSName> tags.osVersion=<OSVersion>

Using PowerShell:

Set-AzVM -ResourceGroupName <ResourceGroupName> -Name <VMName> -Tag @{osName="<OSName>"; osVersion="<OSVersion>"}

Step 3: Create or Update ARM Template

Modify your ARM template to include the custom tags or metadata. Here’s an example snippet:

{
  "type": "Microsoft.Compute/virtualMachines",
  "apiVersion": "2021-07-01",
  "location": "[resourceGroup().location]",
  "properties": {
    "osProfile": {
      "computerName": "[parameters('vmName')]",
      "adminUsername": "[parameters('adminUsername')]",
      "adminPassword": "[parameters('adminPassword')]"
    },
    "tags": {
      "osName": "[parameters('osName')]",
      "osVersion": "[parameters('osVersion')]"
    }
  }
}

Step 4: Create a Custom Policy

Create a custom Azure Policy to enforce the presence of these tags. Here’s an example policy definition:

{
  "properties": {
    "displayName": "Ensure VMs have OS information tags",
    "policyType": "Custom",
    "mode": "Indexed",
    "parameters": {},
    "policyRule": {
      "if": {
        "allOf": [
          {
            "field": "type",
            "equals": "Microsoft.Compute/virtualMachines"
          },
          {
            "field": "tags.osName",
            "exists": "false"
          },
          {
            "field": "tags.osVersion",
            "exists": "false"
          }
        ]
      },
      "then": {
        "effect": "deny"
      }
    }
  }
}

Step 5: Assign the Policy

Assign the custom policy to your subscription or resource group to ensure compliance.