You can only connect to an active user session. If the session is in a disconnected state (due to the RDS session limit/timeout settings), you cannot connect to such a session:

Shadow Error - The specified session is not connected.

Remote Monitoring Request
woshub\administrator is requesting to view your session remotely. Do you accept the request?

Tip. To disconnect from a user session and exit the Shadow mode, press ALT+* on the workstation or Ctrl+* on the RDS server (if no alternative combinations are not set).

Shadow Error: The operator or administrator has refused the request.

You cannot use the tsadmin.msc graphical snap-in from Windows Server 2008 R2 for shadow connections to RDP sessions on newer versions of Windows Server.

Shadow Error: The Group Policy setting is configured to require the user’s consent. Verify the configuration of the policy settings.

To set the parameter of this policy directly through the registry, you can use the command:

You can configure rules for remote shadow connections in the AD domain from the gpmc.msc console using the policy parameter described above, or by using Group Policy Preferences, which directly modify the registry parameter (the latter option allows you to more accurately target the policy to specific computers using the Group Policy Item Level Targeting).

Shadowing RDP Session with PowerShell

You can also use the Remote Desktop Services Shadow features to connect to a user’s session from PowerShell. First of all, you need to get a list of sessions on the RDS host (user sessions will be grouped according to their state):
Get-RDUserSession | ft Username, UnifiedSessionId, SessionState, HostServer, ApplicationType -GroupBy Sessionstate

There are three active RDP user sessions on this server. Let’s connect to the user session with the session ID 3:
Mstsc /shadow:3 /control

Also, to get a list of all RDP sessions on the server (or on the Windows 10 desktop to which multiple RDP connections are allowed), you can use the command:

quser

or

qwinsta

The screen will display a list of RDP user sessions, their IDs and states: Active or Disconnected.

To show the list of sessions on a remote server, run the following command:

query session /server:servername

To connect to a user session on a remote server, use the command:

mstsc /v:rdsh2:3389 /shadow:3 /control

For more convenient shadow connection to RDP user sessions, you can use the following batch script. It prompts you to enter the name of the remote RDS server, displays a list of all sessions and prompts you to specify the session (ID) to which you want to connect to:

shadow.bat

@echo off
set /P rcomp="Enter name or IP of a Remote PC: "
query session /server:%rcomp%
set /P rid="Enter RDP user ID: "
start mstsc /shadow:%rid% /v:%rcomp% /control

You can save this bat file in the %Windir%\System32 directory. As a result, you just need to run the shadow command to start the shadow connection.

You can also use the following PowerShell script with a simple GUI (shadow_user_rdp_session.ps1) for shadow connection:

Add-Type -assembly System.Windows.Forms
$Header = "SESSIONNAME", "USERNAME", "ID", "STATUS"
$gForm = New-Object System.Windows.Forms.Form
$gForm.Text ='Shadow Session Connect'
$gForm.Width = 400
$gForm.AutoSize = $true
$dBttn = New-Object System.Windows.Forms.Button
$dBttn.Text = 'Control'
$dBttn.Location = New-Object System.Drawing.Point(15,10)
$gForm.Controls.Add($dBttn)
$dList = New-Object System.Windows.Forms.ListView
$dList.Location = New-Object System.Drawing.Point(0,50)
$dList.Width = $gForm.ClientRectangle.Width
$dList.Height = $gForm.ClientRectangle.Height
$dList.Anchor = "Top, Left, Right, Bottom"
$dList.MultiSelect = $False
$dList.View = 'Details'
$dList.FullRowSelect = 1;
$dList.GridLines = 1
$dList.Scrollable = 1
$gForm.Controls.add($dList)
foreach ($column in $Header){
$dList.Columns.Add($column) | Out-Null
}
$(qwinsta.exe | findstr "Active") -replace "^[\s>]" , "" -replace "\s+" , "," | ConvertFrom-Csv -Header $Header | ForEach-Object {
$dListItem = New-Object System.Windows.Forms.ListViewItem($_.SESSIONNAME)
$dListItem.Subitems.Add($_.USERNAME) | Out-Null
$dListItem.Subitems.Add($_.ID) | Out-Null
$dListItem.Subitems.Add($_.STATUS) | Out-Null
$dList.Items.Add($dListItem) | Out-Null
}
$dBttn.Add_Click(
{
$SelectedItem = $dList.SelectedItems[0]
if ($SelectedItem -eq $null){
[System.Windows.Forms.MessageBox]::Show("Select a user session to connect ")
}else{
$session_id = $SelectedItem.subitems[2].text
$(mstsc /shadow:$session_id /control)
#[System.Windows.Forms.MessageBox]::Show($session_id)
}
}
)
$gForm.ShowDialog()

This script displays a simple graphical form with a list of active RDP sessions on the local host. You just need to select a user account and click the Connect button.

You can use the shadow user connection not only on Windows Server with the Remote Desktop Services role, but also to connect to users’ desktops running Windows 10 (Using Remote Desktop Session Shadowing Mode in Windows 10).

How-to Allow Non-admin Users to Shadow RDS Sessions?

In the examples above, using the shadow connection to RDS user sessions requires local administrator privileges on the RDS server. However, you can allow a non-admin user to shadow RDP sessions without granting local admin permissions on the computer/server.

For instance, you want to allow members of the AllowRDSShadow group to use a shadow connection to RDP user sessions. Open the elevated command prompt (cmd.exe) and run the command:

wmic /namespace:\\root\CIMV2\TerminalServices PATH Win32_TSPermissionsSetting WHERE (TerminalName=”RDP-Tcp”) CALL AddAccount “woshub\AllowRDSShadow”,2