10 ARM Templates Interview Questions and Answers

ARM (Azure Resource Manager) Templates are a powerful tool for managing and deploying resources in Microsoft Azure. They enable infrastructure as code, allowing for the automation and consistency of resource deployment. By defining the infrastructure in JSON format, ARM Templates provide a declarative way to orchestrate complex environments, making them essential for efficient cloud management.

This article offers a curated selection of interview questions focused on ARM Templates. Reviewing these questions will help you understand key concepts and best practices, ensuring you are well-prepared to discuss and demonstrate your proficiency in using ARM Templates during your interview.

ARM Templates Interview Questions and Answers

1. How do you define and use parameters and variables in an ARM template?

In ARM templates, parameters and variables are essential for creating reusable and flexible templates. Parameters allow you to pass values into the template during deployment, enabling customization without modifying the template itself. Variables store values that can be reused within the template, helping to avoid redundancy and improve readability.

Parameters are defined in the “parameters” section of the template. They can have default values, allowed values, and other constraints. Variables are defined in the “variables” section and can be used to store computed values or constants.

Example:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "storageAccountType": {
      "type": "string",
      "defaultValue": "Standard_LRS",
      "allowedValues": [
        "Standard_LRS",
        "Standard_GRS",
        "Standard_ZRS",
        "Premium_LRS"
      ],
      "metadata": {
        "description": "The type of storage account to create."
      }
    }
  },
  "variables": {
    "storageAccountName": "[concat('stor', uniqueString(resourceGroup().id))]"
  },
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2019-04-01",
      "name": "[variables('storageAccountName')]",
      "location": "[resourceGroup().location]",
      "sku": {
        "name": "[parameters('storageAccountType')]"
      },
      "kind": "StorageV2",
      "properties": {}
    }
  ]
}

In this example, the parameter “storageAccountType” allows the user to specify the type of storage account to create, with a default value of “Standard_LRS”. The variable “storageAccountName” generates a unique storage account name based on the resource group ID.

2. What are some common functions available in ARM templates, and how would you use one in a template?

ARM templates support a variety of built-in functions to help with tasks such as string manipulation, resource identification, and parameter handling. Some common functions include:

• concat: Combines multiple string values into one.
• resourceId: Returns the resource ID for a specified resource.
• parameters: Retrieves the value of a parameter defined in the template.
• variables: Retrieves the value of a variable defined in the template.
• copyIndex: Returns the current iteration index when deploying multiple instances of a resource.
• uniqueString: Generates a unique string based on input values.

To illustrate the use of a function, consider the concat function, which is often used to create resource names dynamically.

Example:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "storageAccountNamePrefix": {
      "type": "string"
    }
  },
  "variables": {
    "storageAccountName": "[concat(parameters('storageAccountNamePrefix'), 'storage')]"
  },
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2019-04-01",
      "name": "[variables('storageAccountName')]",
      "location": "[resourceGroup().location]",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "StorageV2",
      "properties": {}
    }
  ]
}

In this example, the concat function is used to combine a parameter value with a static string to form the name of a storage account.

3. Explain how to implement nested templates and why they might be used.

Nested templates in ARM are used to break down complex deployments into smaller, more manageable components. This modular approach allows for better organization, reusability, and easier maintenance of the infrastructure as code.

Nested templates are implemented by linking or embedding one template within another using the Microsoft.Resources/deployments resource type, which allows you to reference another template file.

Example:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Resources/deployments",
      "apiVersion": "2019-10-01",
      "name": "nestedTemplate",
      "properties": {
        "mode": "Incremental",
        "templateLink": {
          "uri": "https://example.com/nestedTemplate.json",
          "contentVersion": "1.0.0.0"
        }
      }
    }
  ]
}

In this example, the main template references a nested template located at a specified URI.

4. How would you set up a conditional deployment within an ARM template?

Conditional deployment in ARM templates allows you to deploy resources based on specific conditions. This is useful for scenarios where you want to deploy certain resources only if certain conditions are met, such as different environments or specific configurations.

In ARM templates, you can use the “condition” property to specify whether a resource should be deployed. The “condition” property takes a boolean value, which can be derived from parameters or variables defined in the template.

Example:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "deployStorageAccount": {
      "type": "bool",
      "defaultValue": false
    }
  },
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2019-04-01",
      "name": "[concat('storage', uniqueString(resourceGroup().id))]",
      "location": "[resourceGroup().location]",
      "condition": "[parameters('deployStorageAccount')]",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "StorageV2",
      "properties": {}
    }
  ]
}

In this example, the storage account resource will only be deployed if the “deployStorageAccount” parameter is set to true.

5. Describe how to use looping constructs to deploy multiple instances of a resource.

In ARM templates, looping constructs are used to deploy multiple instances of a resource efficiently. This is achieved using the copy element within the resource definition. The copy element allows you to specify the number of iterations and the properties that change with each iteration.

Here is an example of how to use the copy element to deploy multiple instances of a storage account:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2019-04-01",
      "name": "[concat('storageaccount', copyIndex())]",
      "location": "[resourceGroup().location]",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "StorageV2",
      "properties": {},
      "copy": {
        "name": "storageLoop",
        "count": 3
      }
    }
  ]
}

In this example, the copy element is used to create three instances of a storage account. The copyIndex() function is used to append a unique index to the name of each storage account.

6. How do you manage dependencies between resources in an ARM template?

In ARM templates, managing dependencies between resources ensures that resources are created in the correct order. ARM templates use the “dependsOn” property to explicitly define the dependencies between resources.

Example:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2019-04-01",
      "name": "mystorageaccount",
      "location": "[resourceGroup().location]",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "StorageV2",
      "properties": {}
    },
    {
      "type": "Microsoft.Web/serverfarms",
      "apiVersion": "2019-08-01",
      "name": "myAppServicePlan",
      "location": "[resourceGroup().location]",
      "sku": {
        "name": "F1",
        "tier": "Free"
      },
      "properties": {},
      "dependsOn": [
        "[resourceId('Microsoft.Storage/storageAccounts', 'mystorageaccount')]"
      ]
    }
  ]
}

In this example, the App Service Plan resource depends on the Storage Account resource.

7. How do you use resource tags in ARM templates, and why are they important?

Resource tags in ARM templates are used to categorize and manage resources effectively. Tags are key-value pairs that can be applied to resources, resource groups, and subscriptions. They are useful for:

• Cost Management: Tags help in tracking and managing costs by categorizing resources based on departments, projects, or environments.
• Resource Organization: Tags make it easier to locate and manage resources by grouping them logically.
• Automation: Tags can be used in automation scripts to apply policies or perform actions on a specific set of resources.

Here is an example of how to use resource tags in an ARM template:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2019-04-01",
      "name": "mystorageaccount",
      "location": "westus",
      "tags": {
        "environment": "production",
        "department": "finance"
      },
      "properties": {
        "supportsHttpsTrafficOnly": true
      }
    }
  ]
}

In this example, the storage account resource is tagged with “environment” set to “production” and “department” set to “finance”.

8. Can you explain the concept of template specs and how they are used in ARM templates?

Template specs in Azure Resource Manager (ARM) templates are a way to store and manage ARM templates as a resource within Azure. They allow you to create, share, and manage ARM templates more efficiently by storing them in a central location. This makes it easier to reuse templates across different deployments and ensures consistency in resource provisioning.

Template specs are particularly useful in scenarios where you have complex templates or need to maintain multiple versions of a template. By storing these templates as a resource, you can reference them in your deployments without having to manage the template files separately.

To create a template spec, you can use the Azure portal, Azure CLI, or Azure PowerShell. Once created, you can reference the template spec in your ARM templates using the templateSpec resource type.

9. How do you implement secure parameter handling in ARM templates?

In ARM templates, secure parameter handling is essential to protect sensitive information. This can be achieved by using the “secureString” and “secureObject” data types for parameters. These data types ensure that the values are not logged or exposed in deployment outputs.

Example:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "adminPassword": {
      "type": "secureString",
      "metadata": {
        "description": "The password for the administrator account."
      }
    }
  },
  "resources": [
    {
      "type": "Microsoft.Compute/virtualMachines",
      "apiVersion": "2021-03-01",
      "name": "[parameters('vmName')]",
      "location": "[resourceGroup().location]",
      "properties": {
        "osProfile": {
          "adminUsername": "[parameters('adminUsername')]",
          "adminPassword": "[parameters('adminPassword')]"
        }
      }
    }
  ]
}

In this example, the adminPassword parameter is defined as a secureString.

10. Given a scenario where you need to deploy a multi-tier application with a web front-end, database back-end, and load balancer, describe how you would design and implement the ARM template.

To design and implement an ARM template for deploying a multi-tier application with a web front-end, database back-end, and load balancer, you need to define the resources and their dependencies in a JSON format. The key components of the ARM template will include:

• Resource Groups: Define a resource group to contain all the resources.
• Virtual Network and Subnets: Create a virtual network with subnets for the web front-end, database back-end, and load balancer.
• Network Security Groups (NSGs): Define NSGs to control traffic flow between the subnets.
• Load Balancer: Configure a load balancer to distribute traffic to the web front-end instances.
• Web Front-End: Define virtual machines or App Services for the web front-end.
• Database Back-End: Define a database service, such as Azure SQL Database or a virtual machine running a database server.

Example:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Network/virtualNetworks",
      "apiVersion": "2020-06-01",
      "name": "myVNet",
      "location": "[resourceGroup().location]",
      "properties": {
        "addressSpace": {
          "addressPrefixes": ["10.0.0.0/16"]
        },
        "subnets": [
          {
            "name": "webSubnet",
            "properties": {
              "addressPrefix": "10.0.1.0/24"
            }
          },
          {
            "name": "dbSubnet",
            "properties": {
              "addressPrefix": "10.0.2.0/24"
            }
          }
        ]
      }
    },
    {
      "type": "Microsoft.Network/loadBalancers",
      "apiVersion": "2020-06-01",
      "name": "myLoadBalancer",
      "location": "[resourceGroup().location]",
      "properties": {
        "frontendIPConfigurations": [
          {
            "name": "LoadBalancerFrontEnd",
            "properties": {
              "publicIPAddress": {
                "id": "[resourceId('Microsoft.Network/publicIPAddresses', 'myPublicIP')]"
              }
            }
          }
        ],
        "backendAddressPools": [
          {
            "name": "LoadBalancerBackEnd"
          }
        ]
      }
    },
    {
      "type": "Microsoft.Compute/virtualMachines",
      "apiVersion": "2020-06-01",
      "name": "myWebVM",
      "location": "[resourceGroup().location]",
      "properties": {
        "hardwareProfile": {
          "vmSize": "Standard_DS1_v2"
        },
        "osProfile": {
          "computerName": "myWebVM",
          "adminUsername": "azureuser",
          "adminPassword": "Password123!"
        },
        "networkProfile": {
          "networkInterfaces": [
            {
              "id": "[resourceId('Microsoft.Network/networkInterfaces', 'myWebNIC')]"
            }
          ]
        }
      }
    },
    {
      "type": "Microsoft.Sql/servers",
      "apiVersion": "2020-11-01-preview",
      "name": "mySqlServer",
      "location": "[resourceGroup().location]",
      "properties": {
        "administratorLogin": "sqladmin",
        "administratorLoginPassword": "Password123!"
      }
    },
    {
      "type": "Microsoft.Sql/servers/databases",
      "apiVersion": "2020-11-01-preview",
      "name": "myDatabase",
      "location": "[resourceGroup().location]",
      "dependsOn": [
        "[resourceId('Microsoft.Sql/servers', 'mySqlServer')]"
      ],
      "properties": {
        "collation": "SQL_Latin1_General_CP1_CI_AS",
        "maxSizeBytes": "2147483648",
        "sampleName": "AdventureWorksLT"
      }
    }
  ]
}