Tutorial: Install applications in Virtual Machine Scale Sets with Azure PowerShell

To run applications on virtual machine (VM) instances in a scale set, you first need to install the application components and required files. In a previous tutorial, you learned how to create and use a custom VM image to deploy your VM instances. This custom image included manual application installs and configurations. You can also automate the install of applications to a scale set after each VM instance is deployed, or update an application that already runs on a scale set. In this tutorial you learn how to:

  • Automatically install applications to your scale set
  • Use the Azure Custom Script Extension
  • Update a running application on a scale set

If you don't have an Azure subscription, create a free account before you begin.

Azure Cloud Shell

Azure hosts Azure Cloud Shell, an interactive shell environment that you can use through your browser. You can use either Bash or PowerShell with Cloud Shell to work with Azure services. You can use the Cloud Shell preinstalled commands to run the code in this article, without having to install anything on your local environment.

To start Azure Cloud Shell:

Option Example/Link
Select Try It in the upper-right corner of a code or command block. Selecting Try It doesn't automatically copy the code or command to Cloud Shell. Screenshot that shows an example of Try It for Azure Cloud Shell.
Go to https://shell.azure.com, or select the Launch Cloud Shell button to open Cloud Shell in your browser. Button to launch Azure Cloud Shell.
Select the Cloud Shell button on the menu bar at the upper right in the Azure portal. Screenshot that shows the Cloud Shell button in the Azure portal

To use Azure Cloud Shell:

  1. Start Cloud Shell.

  2. Select the Copy button on a code block (or command block) to copy the code or command.

  3. Paste the code or command into the Cloud Shell session by selecting Ctrl+Shift+V on Windows and Linux, or by selecting Cmd+Shift+V on macOS.

  4. Select Enter to run the code or command.

What is the Azure Custom Script Extension?

The Custom Script Extension downloads and executes scripts on Azure VMs. This extension is useful for post deployment configuration, software installation, or any other configuration / management task. Scripts can be downloaded from Azure storage or GitHub, or provided to the Azure portal at extension run-time.

The Custom Script extension integrates with Azure Resource Manager templates. It can also be used with the Azure CLI, Azure PowerShell, Azure portal, or the REST API. For more information, see the Custom Script Extension overview.

To see the Custom Script Extension in action, create a scale set that installs the IIS web server and outputs the hostname of the scale set VM instance. The Custom Script Extension definition downloads a sample script from GitHub, installs the required packages, then writes the VM instance hostname to a basic HTML page.

Create a scale set

Now create a Virtual Machine Scale Set with New-AzVmss. To distribute traffic to the individual VM instances, a load balancer is also created. The load balancer includes rules to distribute traffic on TCP port 80. It also allows remote desktop traffic on TCP port 3389 and PowerShell remoting on TCP port 5985. When prompted, you can set your own administrative credentials for the VM instances in the scale set:

New-AzVmss `
  -ResourceGroupName "myResourceGroup" `
  -VMScaleSetName "myScaleSet" `
  -OrchestrationMode "Flexible" `
  -Location "EastUS" `
  -VirtualNetworkName "myVnet" `
  -SubnetName "mySubnet" `
  -PublicIpAddressName "myPublicIPAddress" `
  -LoadBalancerName "myLoadBalancer" 

It takes a few minutes to create and configure all the scale set resources and VMs.

Create Custom Script Extension definition

Azure PowerShell uses a hashtable to store the file to download and the command to execute. In the following example, a sample script from GitHub is used. First, create this configuration object as follows:

$customConfig = @{
  "fileUris" = (,"https://raw.githubusercontent.com/Azure-Samples/compute-automation-configurations/master/automate-iis.ps1");
  "commandToExecute" = "powershell -ExecutionPolicy Unrestricted -File automate-iis.ps1"

Now, apply the Custom Script Extension with Add-AzVmssExtension. The configuration object previously defined is passed to the extension. Update and run the extension on the VM instances with Update-AzVmss.

# Get information about the scale set
$vmss = Get-AzVmss `
  -ResourceGroupName "myResourceGroup" `
  -VMScaleSetName "myScaleSet"

# Add the Custom Script Extension to install IIS and configure basic website
$vmss = Add-AzVmssExtension `
  -VirtualMachineScaleSet $vmss `
  -Name "customScript" `
  -Publisher "Microsoft.Compute" `
  -Type "CustomScriptExtension" `
  -TypeHandlerVersion 1.9 `
  -Setting $customConfig

# Update the scale set and apply the Custom Script Extension to the VM instances
Update-AzVmss `
  -ResourceGroupName "myResourceGroup" `
  -Name "myScaleSet" `
  -VirtualMachineScaleSet $vmss

Each VM instance in the scale set downloads and runs the script from GitHub. In a more complex example, multiple application components and files could be installed. If the scale set is scaled up, the new VM instances automatically apply the same Custom Script Extension definition and install the required application.

Allow traffic to application

To allow access to the basic web application, create a network security group with New-AzNetworkSecurityRuleConfig and New-AzNetworkSecurityGroup. For more information, see Networking for Azure Virtual Machine Scale Sets.

#Create a rule to allow traffic over port 80
$nsgFrontendRule = New-AzNetworkSecurityRuleConfig `
  -Name myFrontendNSGRule `
  -Protocol Tcp `
  -Direction Inbound `
  -Priority 200 `
  -SourceAddressPrefix * `
  -SourcePortRange * `
  -DestinationAddressPrefix * `
  -DestinationPortRange 80 `
  -Access Allow

#Create a network security group and associate it with the rule
$nsgFrontend = New-AzNetworkSecurityGroup `
  -ResourceGroupName  "myResourceGroup" `
  -Location EastUS `
  -Name myFrontendNSG `
  -SecurityRules $nsgFrontendRule

$vnet = Get-AzVirtualNetwork `
  -ResourceGroupName  "myResourceGroup" `
  -Name myVnet

$frontendSubnet = $vnet.Subnets[0]

$frontendSubnetConfig = Set-AzVirtualNetworkSubnetConfig `
  -VirtualNetwork $vnet `
  -Name mySubnet `
  -AddressPrefix $frontendSubnet.AddressPrefix `
  -NetworkSecurityGroup $nsgFrontend

Set-AzVirtualNetwork -VirtualNetwork $vnet

Test your scale set

To see your web server in action, get the public IP address of your load balancer with Get-AzPublicIpAddress. The following example displays the IP address created in the myResourceGroup resource group:

Get-AzPublicIpAddress -ResourceGroupName "myResourceGroup" | Select IpAddress

Enter the public IP address of the load balancer in to a web browser. The load balancer distributes traffic to one of your VM instances, as shown in the following example:

Basic web page in IIS

Leave the web browser open so that you can see an updated version in the next step.

Update app deployment

Throughout the lifecycle of a scale set, you may need to deploy an updated version of your application. With the Custom Script Extension, you can reference an updated deploy script and then reapply the extension to your scale set. When the scale set was created in a previous step, the -UpgradePolicyMode was set to Automatic. This setting allows the VM instances in the scale set to automatically update and apply the latest version of your application.

Create a new config definition named customConfigv2. This definition runs an updated v2 version of the application install script:

$customConfigv2 = @{
  "fileUris" = (,"https://raw.githubusercontent.com/Azure-Samples/compute-automation-configurations/master/automate-iis-v2.ps1");
  "commandToExecute" = "powershell -ExecutionPolicy Unrestricted -File automate-iis-v2.ps1"

Update the Custom Script Extension configuration to the VM instances in your scale set. The customConfigv2 definition is used to apply the updated version of the application:

$vmss = Get-AzVmss `
  -ResourceGroupName "myResourceGroup" `
  -VMScaleSetName "myScaleSet"
$vmss.VirtualMachineProfile.ExtensionProfile[0].Extensions[0].Settings = $customConfigv2
Update-AzVmss `
  -ResourceGroupName "myResourceGroup" `
  -Name "myScaleSet" `
  -VirtualMachineScaleSet $vmss

All VM instances in the scale set are automatically updated with the latest version of the sample web page. To see the updated version, refresh the web site in your browser:

Updated web page in IIS

Clean up resources

To remove your scale set and additional resources, delete the resource group and all its resources with Remove-AzResourceGroup. The -Force parameter confirms that you wish to delete the resources without an additional prompt to do so. The -AsJob parameter returns control to the prompt without waiting for the operation to complete.

Remove-AzResourceGroup -Name "myResourceGroup" -Force -AsJob

Next steps

In this tutorial, you learned how to automatically install and update applications on your scale set with Azure PowerShell:

  • Automatically install applications to your scale set
  • Use the Azure Custom Script Extension
  • Update a running application on a scale set

Advance to the next tutorial to learn how to automatically scale your scale set.