Creating Template Linkages and Dependencies | Azure ARM Tutorial

Welcome to the tutorial on creating template linkages and dependencies in ARM templates for Azure Resource Manager. ARM templates provide a powerful way to define and deploy infrastructure and applications in Azure. By establishing linkages and dependencies between templates, you can modularize your deployments and ensure proper sequencing and configuration of resources.

1. Using Template Linkages

Template linkages allow you to reference and deploy other ARM templates within your main template. This enables you to break down complex deployments into smaller, manageable units.


"resources": [
  {
    "type": "Microsoft.Resources/deployments",
    "apiVersion": "2021-04-01",
    "name": "linkedTemplateDeployment",
    "properties": {
      "mode": "Incremental",
      "templateLink": {
        "uri": "[uri(variables('linkedTemplateUri'))]",
        "contentVersion": "1.0.0.0"
      },
      "parameters": {
        "param1": {
          "value": "myValue"
        }
      }
    }
  }
]

2. Establishing Template Dependencies

Template dependencies define the order in which resources are deployed. By specifying dependencies, you ensure that resources are created in the correct sequence, considering their interdependencies.


"resources": [
  {
    "type": "Microsoft.Storage/storageAccounts",
    "name": "myStorageAccount",
    "apiVersion": "2021-04-01",
    ...
  },
  {
    "type": "Microsoft.Compute/virtualMachines",
    "name": "myVM",
    "apiVersion": "2021-03-01",
    "dependsOn": [
      "Microsoft.Storage/storageAccounts/myStorageAccount"
    ],
    ...
  }
]

3. Steps to Create Template Linkages and Dependencies

Follow these steps to create template linkages and dependencies in your ARM templates:

Step 1: Define Template Linkages

Create a resource of type Microsoft.Resources/deployments within your ARM template. Specify the URI of the linked template and provide any required parameters.


"resources": [
  {
    "type": "Microsoft.Resources/deployments",
    "apiVersion": "2021-04-01",
    "name": "linkedTemplateDeployment",
    "properties": {
      "mode": "Incremental",
      "templateLink": {
        "uri": "[uri(variables('linkedTemplateUri'))]",
        "contentVersion": "1.0.0.0"
      },
      "parameters": {
        "param1": {
          "value": "myValue"
        }
      }
    }
  }
]

Step 2: Define Template Dependencies

Specify dependencies between resources by using the dependsOn property within the resource definition. List the fully qualified resource IDs that the resource depends on.


"resources": [
  {
    "type": "Microsoft.Compute/virtualMachines",
    "name": "myVM",
    "apiVersion": "2021-03-01",
    "dependsOn": [
      "Microsoft.Storage/storageAccounts/myStorageAccount"
    ],
    ...
  }
]

Mistakes to Avoid

Not properly specifying the URI or content version in the template linkage.
Missing or incorrect usage of the dependsOn property for resource dependencies.
Not considering the order of resource creation and their interdependencies when defining dependencies.

Frequently Asked Questions (FAQs)

Q: Can I use template linkages to deploy templates from different locations?
A: Yes, template linkages can be used to reference templates from different locations, including remote URLs or storage accounts within Azure.
Q: Can I have circular dependencies between resources in ARM templates?
A: No, circular dependencies are not supported in ARM templates. You need to ensure that your template dependencies do not create circular references.
Q: Can I use template linkages and dependencies across resource groups or subscriptions?
A: Yes, template linkages and dependencies can be established across resource groups and subscriptions. Ensure that you have the necessary permissions and access rights to the target resources.
Q: Can I deploy multiple linked templates from a single main template?
A: Yes, you can deploy multiple linked templates from a single main template by adding multiple deployment resources within the main template.
Q: Can I use parameters in linked templates?
A: Yes, you can pass parameters to linked templates to customize their behavior and configuration.

Summary

In this tutorial, you learned how to create template linkages and dependencies in ARM templates for Azure Resource Manager. Template linkages enable you to reference and deploy other templates, allowing you to modularize complex deployments. Template dependencies ensure proper sequencing and configuration of resources. By leveraging these features, you can create more organized and structured ARM templates for your Azure deployments.