When deploying Azure Virtual Machines (VMs) - individually or within a Virtual Machine Scale Set (VMSS) - administrators often need to automate post-deployment configuration tasks such as installing software, running configuration scripts, or setting up environment dependencies.
According to Microsoft Azure Administrator documentation, the Azure Custom Script Extension is designed precisely for this purpose. It downloads and executes scripts on Azure VMs after deployment. The extension integrates directly with Azure Resource Manager (ARM) templates, Azure CLI, or PowerShell, enabling automated installation and configuration of software packages like NGINX, IIS, or custom utilities.
The Custom Script Extension runs PowerShell scripts on Windows VMs and shell scripts on Linux VMs. In the case of deploying Windows Server 2022 VMs in a scale set, you can embed the Custom Script Extension JSON configuration into your ARM template, specifying the script's location in Azure Storage or GitHub and the command to execute (for example, Install-WindowsFeature Web-Server or an NGINX installer command).
This approach aligns with Microsoft's best practices for Azure automation and infrastructure-as-code, ensuring consistent, repeatable deployments across all instances in the scale set. It also minimizes manual intervention, reduces configuration drift, and ensures each VM instance has the required software components available immediately after provisioning.