Custom Script extension not Executing on VMSS - terraform

Question

I am creating a VMSS using terraform to use for Azure Devops agent pool. I'm able to create VMSS successfully but when I try to run script to enroll it to agent pool, I'm hitting a wall. Nothing seems to work. Here is my TF code:
data "local_file" "template" {
filename = "./agent_install_script.ps1"
}
data "template_file" "script" {
template = data.local_file.template.content
vars = {
agent_name = var.agent_name
pool_name = var.agent_pool_name
token = var.pat_token
user_name = var.vmss_admin_username
logon_password = random_password.vm_password.result
}
}
module "vmss_windows2022g2" {
source = "../modules/vmss_windows"
environment = var.environment
resource_group_name = var.resource_group
vmss_sku = "Standard_DS2_v2"
vmss_nic_subnet_id = module.vnet_mgt.subnet_windows_vmss_id
vmss_nsg_id = module.nsg.vmss_nsg_id
vmss_computer_name = "win2022g2"
vmss_admin_username = var.vmss_admin_username
vmss_admin_password = random_password.vm_password.result
windows_image_id = data.azurerm_image.windows_server2022_gen2.id
vmss_storage_uri = data.azurerm_storage_account.vm_storage.primary_blob_endpoint
overprovision = false
#this will be stored at %SYSTEMDRIVE%\AzureData\CustomData.bin
customData = data.template_file.script.rendered
tags = local.env_tags_map
}
resource "azurerm_virtual_machine_scale_set_extension" "ext" {
name = "InstallDevOpsAgent"
virtual_machine_scale_set_id = module.vmss_windows2022g2.id
publisher = "Microsoft.Azure.Extensions"
type = "CustomScript"
type_handler_version = "2.0"
settings = jsonencode({
"commandToExecute" = "dir C:\\ > C:\\temp\\test.txt"
#"cd C:\\AzureData; mv .\\CustomData.bin .\\install_agent.ps1; powershell -ExecutionPolicy Unrestricted -File .\\install_agent.ps1; del .\\install_agent.ps1;"
})
#protected_settings = var.protected_settings
failure_suppression_enabled = false
auto_upgrade_minor_version = false
automatic_upgrade_enabled = false
provision_after_extensions = []
timeouts {
create = "1h"
}
}
As you can see, I'm copying the powershell script via custom_data and that is working fine with all the variables substituted properly. I have tried executing simple command dir C:\\ > C:\\temp\\test.txt to see if anything works, but am not getting any output.
TF version 1.12, azurerm provider version 3.32.0

Answer 1

Azure DevOps should install an extension on the scale set (and in turn the VM's) which will automatically enrol the agent without the need for a script.
More details here:
https://learn.microsoft.com/en-us/azure/devops/pipelines/agents/scale-set-agents?view=azure-devops#lifecycle-of-a-scale-set-agent