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Create and manage ARM templates for VMs in DevTest Labs

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This article describes how Azure DevTest Labs users can:

  • View, edit, and save Azure Resource Manager (ARM) templates for creating Azure VMs.
  • Store ARM templates in source control repositories.
  • Add and access ARM template repositories in Azure DevTest Labs.

An Azure Resource Manager template is a JavaScript Object Notation (JSON) file that defines the infrastructure and configuration for your project. The template uses declarative syntax. You describe your intended deployment without writing the sequence of programming commands to create the deployment.

ARM templates for VM creation use the Microsoft.DevTestLab/labs/virtualmachines resource type. Each lab VM created with this resource type appears as a separate item in the lab's My virtual machines list.

Lab users can create their own ARM templates, modify existing ARM templates to meet their needs, or access preconfigured templates from private repositories or the public DevTest Labs GitHub repository to use in creating VMs.

Prerequisites

  • To view or save ARM templates while creating VMs, at least DevTest Lab User role in a lab.
  • To enable public repositories or add private template repositories to labs, at least Contributor role in the lab.

View and save ARM templates for VMs

You can customize and use an ARM template from any available Azure VM base to use for deploying more VMs of the same type. To customize and save an ARM template in the Azure portal:

  1. On your lab's Overview page, select Add on the top toolbar.

  2. On the Choose a base page, select the VM base you want.

  3. On the Create lab resource tabs, configure settings and add desired artifacts to your template VM.

  4. On the Advanced Settings tab, select View ARM template under Automation at the bottom of the form.

  5. Copy and save the contents of the View Azure Resource Manager template page as a file named azuredeploy.json, and then close the page.

    Screenshot that shows an ARM template to save for later use.

  6. If you want to create the VM immediately, select Create at the bottom of the Create lab resource page.

For more information on creating lab VMs, see Create lab virtual machines in Azure DevTest Labs.

Edit ARM templates

When you reuse the ARM template to create more VMs, you can change the parameters and values in your template file. To update only the template parameters section without having to edit the main template file, you can create and edit a separate file called azuredeploy.parameters.json.

For example, in training, demo, and trial scenarios, you can automatically delete VMs after a certain date so they don't keep incurring costs. When you create a lab VM in the Azure portal, you can specify the Expiration date on the Advanced settings tab. You can also add an expirationDate parameter or change its value in an ARM template.

  "parameters": {
    "expirationDate": {
      "type": "string",
      "defaultValue": "2025-03-15T07:00:00.000Z"
    }
  }

For an example template, see Create a new VM in a lab with a specified expiration date.

Tip

To create a URI value for automatically managing nested templates, you can add the _artifactsLocation and _artifactsLocationSasToken parameters to your parameters section or file. For more information about nested templates, see Deploy nested Azure Resource Manager templates for testing environments.

Create multiple VMs at once

In the Azure portal, you can create more than one VM at a time by specifying Number of instances on the Advanced Settings tab of the DevTest Labs VM creation screen. In an ARM template, you can add or edit the copy element in the resources section to specify the number of instances to create. For example:

      "copy": {
        "name": "[parameters('newVMName')]",
        "count": 2
      },

For more information about creating more than one instance of a VM in your ARM template, see Resource iteration in ARM templates.

Store ARM templates in Git repositories

As a best practice for infrastructure as code and configuration as code, store your ARM templates in source control. DevTest Labs can load ARM templates directly from GitHub or Azure Repos source control repositories. You can then use the templates throughout your release cycle, from development through test to production environments.

Use the following file structure to store an ARM template in a source control repository:

  • Name the main template file azuredeploy.json.
  • Name any standalone parameter customization file azuredeploy.parameters.json.
  • Optionally, define metadata such as template display name and description in a file named metadata.json.

The following screenshot shows a typical ARM template folder structure in a repository.

Screenshot that shows key ARM template files in a repository.

Access template repositories for labs

To see and access the template repositories available to your lab:

  1. On the lab's Overview page in the Azure portal, select Configuration and policies from the left navigation.
  2. On the Configuration and policies page, select Repositories under External resources in the left navigation.
  3. Copy the Git Clone URLs and connect to the repos to access the templates.

Screenshot that shows the Repositories configuration screen.

The Public Artifact Repo and Public Environment Repo at the DevTest Labs public GitHub repository are available for all labs. If these repos aren't enabled for your lab, a lab owner or contributor can enable them by selecting the checkboxes next to Public Artifact Repo and Public Environment Repo, and then selecting Enable on the top menu bar. For more information, see Enable and configure public environments.

Add template repositories to labs

Lab owners or contributors can add ARM template repositories to their labs so all lab users can access the templates. To add a repo to your lab:

  1. Select Add in the top menu bar of the Repositories page.
  2. On the Repository screen, enter the following information:
    • Name: Repository name.
    • Git clone URL: The Git HTTPS clone URL from GitHub.
    • Branch (optional): The branch that has the ARM template definitions.
    • Azure Resource Manager template folder path: The folder path, relative to the Git clone URI, for the ARM template definitions.
    • Authentication type: The authentication method to securely access the repository: Personal access token or GitHub App.
      • To get a personal access token, select your profile in GitHub and then select Settings > Developer settings > Personal access tokens.
      • To use the GitHub app, select Sign in with GitHub and sign in if necessary. You must have the Microsoft DevCenter GitHub App installed.
  3. Select Save.

Screenshot that shows GitHub settings for adding a new template repository to a lab.

The repository now appears in the Repositories list for the lab. Lab users can use the repository templates to create multi-VM DevTest Labs environments. Lab administrators can use the templates to automate lab deployment and management tasks.

Use ARM templates to deploy VMs

To create and deploy Azure VMs by using ARM templates, you can use any of the following methods:

For more information about deployment, see Template deployment process.

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