Configure Start VM on Connect

Start VM on Connect lets you reduce costs by enabling end users to power on the virtual machines (VMs) used as session hosts only when they're needed. You can then power off VMs when they're not needed.

For personal host pools, Start VM on Connect only powers on an existing session host VM that is already assigned or can be assigned to a user. For pooled host pools, Start VM on Connect only powers on a session host VM when none are turned on and more VMs are only be turned on when the first VM reaches the session limit.

The time it takes for a user to connect to a remote session on a session host that is powered off (deallocated) increases because the VM needs time to power on again, much like turning on a physical computer. When a user uses Windows App and the Remote Desktop app to connect to Azure Virtual Desktop, they're told a VM is being powered on while they're connecting.

You can enable Start VM on Connect for session hosts on Azure and Azure Local in personal or pooled host pools using the Azure portal, Azure PowerShell, or Azure CLI. Start VM on Connect is configured per host pool.

Prerequisites

Before you can use Start VM on Connect, you need:

• An existing host pool that's associated with an application group and workspace. You can only configure Start VM on Connect on existing host pools. You can't enable it at the same time you create a new host pool.

• The Azure account you use to configure Start VM on Connect must have the Desktop Virtualization Host Pool Contributor role-based access control (RBAC) role assigned.

• Windows App or the Remote Desktop app installed on a local device with a user account assigned to a desktop or application in the application group you can test with.

• Make sure that the name of the host pool, session hosts in that host pool, and the resource group only have ANSI characters.

• If you want to use Azure PowerShell or Azure CLI locally, see Use Azure PowerShell and Azure CLI with Azure Virtual Desktop to make sure you have the Az.DesktopVirtualization PowerShell module or the desktopvirtualization Azure CLI extension installed. Alternatively, use the Azure Cloud Shell.

Assign the Desktop Virtualization Power On Contributor role with the Azure portal

To configure Start VM on Connect, you need to assign the Desktop Virtualization Power On Contributor role-based access control (RBAC) role to the Azure Virtual Desktop service principal with your Azure subscription as the assignable scope. If you assign this role at any level lower than a subscription, such as the resource group, host pool, or VM, prevents Start VM on Connect from working properly.

You need to add each Azure subscription that contains host pools and session host VMs you want to use with Start VM on Connect as an assignable scope. This role assignment allows Azure Virtual Desktop to power on VMs, check their status, and report diagnostic information for those subscriptions.

To learn how to assign the Desktop Virtualization Power On Contributor role to the Azure Virtual Desktop service principal, see Assign Azure RBAC roles or Microsoft Entra roles to the Azure Virtual Desktop service principals.

Enable or disable Start VM on Connect

Once you assign the Desktop Virtualization Power On Contributor role to the service principal on relevant subscriptions, you can configure Start VM on Connect using the Azure portal, Azure PowerShell, or Azure CLI.

Azure portal

To configure Start VM on Connect using the Azure portal:

1. Sign in to the Azure portal.

2. In the search bar, enter Azure Virtual Desktop and select the matching service entry.

3. Select Host pools, then select the name of the host pool where you want to enable the setting.

4. Select Properties.

5. In the configuration section, set Start VM on connect to Yes to enable it, or No to disable it.

6. Select Save to apply the settings.

Azure PowerShell

Here's how to configure Start VM on Connect using Azure PowerShell. You need to make sure you have the names of the resource group and host pool you want to configure. Be sure to change the <placeholder> values for your own.

1. Open Azure Cloud Shell in the Azure portal with the PowerShell terminal type, or run PowerShell on your local device.

   • If you're using Cloud Shell, make sure your Azure context is set to the subscription that you want to use.

   • If you're using PowerShell locally, first sign in with Azure PowerShell, and then make sure your Azure context is set to the subscription that you want to use.

2. To enable or disable Start VM on Connect, do one of the following steps:

   • To enable Start VM on Connect, run the following command, replacing the value for -ResourceGroupName and -Name with your values:

     Update-AzWvdHostPool -ResourceGroupName <resourcegroupname> -Name <hostpoolname> -StartVMOnConnect:$true
     

   • To disable Start VM on Connect, run the following command, replacing the value for -ResourceGroupName and -Name with your values:

     Update-AzWvdHostPool -ResourceGroupName <resourcegroupname> -Name <hostpoolname> -StartVMOnConnect:$false
     

Azure CLI

Here's how to configure Start VM on Connect using Azure CLI. You need to make sure you have the names of the resource group and host pool you want to configure. Be sure to change the <placeholder> values for your own.

1. Open Azure Cloud Shell in the Azure portal with the Bash terminal type, or run the Azure CLI on your local device.

   • If you're using Cloud Shell, make sure your Azure context is set to the subscription that you want to use.

   • If you're using the Azure CLI locally, first sign in with the Azure CLI, and then make sure your Azure context is set to the subscription that you want to use.

2. To enable or disable Start VM on Connect, do one of the following steps:

   • To enable Start VM on Connect, run the following command, replacing the value for --resource-group and --name with your values:

     az desktopvirtualization hostpool update \
          --resource-group $resourceGroupName \
          --name $hostPoolName \
          --start-vm-on-connect true
     

   • To disable Start VM on Connect, run the following command, replacing the value for --resource-group and --name with your values:

     az desktopvirtualization hostpool update \
          --resource-group $resourceGroupName \
          --name $hostPoolName \
          --start-vm-on-connect false
     

Note

For pooled host pools, Start VM on Connect will start a VM every five minutes at most. If other users try to sign in during this five-minute period and there still aren't any available resources, Start VM on Connect won't start a new VM. Instead, the users trying to sign in will receive an error message that says, No resources available. They should wait a few minutes and try to connect again.

Troubleshooting

If the session host VM doesn't power on, you need to check the health of the VM you tried to power on as a first step. You can also view Azure Virtual Desktop logs in Log Analytics to check for problems. If you receive an error message, make sure to pay close attention to the message content and make a note of the error name for reference. You can also use Azure Virtual Desktop Insights to get suggestions for how to resolve issues.

Note

Connecting to a session host outside of the Azure Virtual Desktop service that is powered off, such as by directly connecting to a VM by IP address or name, the VM isn't started.

Related content

For more information about Start VM on Connect, see our Start VM on Connect FAQ.