Describe Azure Resource Manager and Azure Resource Manager templates (ARM templates)

Azure Resource Manager (ARM) is a service provided by Microsoft Azure for the deployment, management, and monitoring of resources in the cloud. It acts as a layer that allows users to create, update, and delete resources within their Azure subscription. Resource Manager enables us to work with the resources in our solution as a group, rather than handling them individually.

Understanding Azure Resource Manager

With ARM, users can:

• Deploy, manage, and monitor all the resources for your solution as a group, rather than handling these resources individually.
• Repeatedly deploy your solution throughout the development lifecycle and have confidence your resources are deployed in a consistent state.
• Manage your infrastructure through declarative templates rather than scripts.
• Define dependencies between resources so they’re deployed in the correct order.
• Apply access control to all services in your resource group because Role-Based Access Control (RBAC) is natively integrated into the management platform.
• Apply tags to resources to logically organize all the resources in your subscription.

ARM Templates

One of the key features of ARM is ARM templates, which are JSON files that define the resources you need to deploy for your solution. Think of an ARM template as a blueprint for your Azure applications or solutions.

ARM templates allow you to:

• Deploy complex environments repeatedly and consistently.
• Simplify the code for your deployment because you don’t have to write separate scripts to provision each resource.
• Review and validate your templates before deployment to know exactly what will happen when you deploy them.

The structure of an ARM template is typically divided into the following sections:

• $schema: Specifies the location of the JSON schema file that describes the version of the template language.
• contentVersion: Specifies the version of the ARM template (user-defined).
• parameters: Provide values during deployment that allow the same template to be used with different environments.
• variables: Define values that are reused in your templates. They can be constructed from parameter values.
• functions: Create customized functions that you can call within the template to define complex expressions.
• resources: Specify the resources to deploy.
• outputs: Return values from the deployed resources.

Example of ARM Template

{
<span>”$schema”: “https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#”, </span>
<span>”contentVersion”: “1.0.0.0”,</span>
<span>”parameters”: {</span>
<span>”storageAccountName”: {</span>
<span>”type”: “string”,</span>
<span>”metadata”: {</span>
<span>”description”: “Name of the storage account”</span>
<span>}</span>
<span>}</span>
<span>},</span>
<span>”variables”: {</span>
<span>”location”: “westus”</span>
<span>},</span>
<span>”resources”: [</span>
<span>{</span>
<span>”type”: “Microsoft.Storage/storageAccounts”,</span>
<span>”apiVersion”: “2019-06-01″,</span>
<span>”name”: “[parameters(‘storageAccountName’)]”,</span>
<span>”location”: “[variables(‘location’)]”,</span>
<span>”sku”: {</span>
<span>”name”: “Standard_LRS”</span>
<span>},</span>
<span>”kind”: “StorageV2″,</span>
<span>”properties”: {}</span>
<span>}</span>
<span>],</span>
<span>”outputs”: {</span>
<span>”storageAccountName”: {</span>
<span>”type”: “string”,</span>
<span>”value”: “[parameters(‘storageAccountName’)]”</span>
<span>}</span>
<span>}</span>
}

In this example, an ARM template is defined to create a storage account. It uses a parameter to receive the storage account name and a variable for the location. The resource section defines the storage account with the necessary properties and apiVersion. This allows for a standard deployment pattern across different environments such as development, testing, and production.

When deploying resources using ARM templates, the deployment can be done in incremental mode or complete mode:

• Incremental mode: Only adds or modifies the resources defined in the template. Existing resources that are not specified in the template are unaffected.
• Complete mode: Besides adding or modifying resources, it also deletes resources that exist in the resource group but are not specified in the template.

In conclusion, Azure Resource Manager and ARM templates give you a powerful, efficient, and flexible toolset to manage and deploy Azure resources, offering consistency, repeatability, and infrastructure as code for your Azure environments. Understanding and utilizing ARM and ARM templates is essential for anyone looking to work extensively within Azure and is especially relevant for the AZ-900 Microsoft Azure Fundamentals exam.