One thing I do hate in the new Windows 2012 Core setup is that PowerShell is not the default shell when one logs in. Microsoft made it so that in Core most of the Administration task are done via PowerShell or Remote Administratio tools. The fist thing one must do is to take ownership of the HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\AlternateShells\AvailableShells Registry key since we will be modifying it. To achieve this Microsoft was nice enough to include the GUI version of the registry editor so we only need to type regedit in the command prompt and hit enter, after it comes up we can navigate to the key We right-click on the Key AvailableShells and click on Permission, on Permissions click on Advanced and click on Change Add the Administrator account, click on OK and on the previous screen click on Apply. Create a registry value under the key with the name of 40000 and set the value to:

powershell.exe -noexit -command "& {set-location $env:userprofile; clear-host}"

Now when you log off and log back in you will be greeted with a PowerShell window.

The reason why we use 40000 is that when you install the full GUI Explorer.exe will be 90000 and we want to PowerShell to be the Shell only if we are in Core or in Server-Gui-Mgmt-Infra.

To make life simpler here is a script you can either copy and paste in to a PowerShell window or create a .ps1 file and execute from there:

# Use C# to leverage the Win32API
$definition = @"
using System;
using System.Runtime.InteropServices;   
namespace Win32Api
{
    public class NtDll 
    {  
        [DllImport("ntdll.dll", EntryPoint="RtlAdjustPrivilege")]  
         public static extern int RtlAdjustPrivilege(ulong Privilege, bool Enable, bool CurrentThread, ref bool Enabled); 
    } 
}
"@
Add-Type -TypeDefinition $definition -PassThru
$bEnabled = $false
 
 
# Enable SeTakeOwnershipPrivilege
$res = [Win32Api.NtDll]::RtlAdjustPrivilege(9, $true, $false, [ref]$bEnabled)
  
# Take ownership of the registry key
$key = [Microsoft.Win32.Registry]::LocalMachine.OpenSubKey('SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\AlternateShells', [Microsoft.Win32.RegistryKeyPermissionCheck]::ReadWriteSubTree,[System.Security.AccessControl.RegistryRights]::takeownership)
$acl = $key.GetAccessControl()
$acl.SetOwner([System.Security.Principal.NTAccount]"Administrators")

# Set Full Control for Administrators
$rule = New-Object System.Security.AccessControl.RegistryAccessRule("Administrators","FullControl", "Allow")
$acl.AddAccessRule($rule)
[void]$key.SetAccessControl($acl)
# Create Registry Value
[void][Microsoft.Win32.Registry]::SetValue($key,"90000",'powershell.exe -noexit -command "& {set-location $env:userprofile; clear-host}"')

I hope you found the blog post information useful.

Shell is Only the Beginning

Set PowerShell as Your Default Shell in Windows 2012 Core