windows_vhdx_boot.txt

Commands to add an existing VHD/VHDx to your boot menu:

$regex = [regex] "\{\w{8}-\w{4}-\w{4}-\w{4}-\w{12}\}"
$new_guid=$(bcdedit /copy `{current`} /d "entry_name")
$new_guid=$regex.match($new_guid).value

bcdedit /set $new_guid device vhd=[C:]\Image.vhdx
bcdedit /set $new_guid osdevice vhd=[C:]\Image.vhdx
bcdedit /set $new_guid detecthal on
bcdedit /set $new_guid debug off
bcdedit /default $new_guid
bcdedit /timeout 10

Enable Hyper-V role:

# Mount the VHD or VHDX file
$mountedVHD = [string](Mount-VHD -Path $VHDImage -Passthru | Get-Disk | Get-Partition | `
  Get-Volume | Where-Object -Property FileSystemLabel -NE "System Reserved").DriveLetter + ":\"
$mountedVHD = $mountedVHD.Substring($mountedVHD.Length-3,3)

Resize-VHD $VHDImage -SizeBytes

dism /Image:$mountedVHD /Enable-Feature /FeatureName:Microsoft-Hyper-V /All
dism /Image:$mountedVHD /Enable-Feature /FeatureName:RSAT-Hyper-V-Tools-Feature /All
dism /Image:$mountedVHD /Enable-Feature /FeatureName:Microsoft-Hyper-V-Management-Clients /All
dism /Image:$mountedVHD /Enable-Feature /FeatureName:Microsoft-Hyper-V-Management-PowerShell /All

$MaxSize = (Get-PartitionSupportedSize -DriveLetter E).sizeMax
Resize-Partition -DriveLetter E -Size $MaxSize

Dismount-VHD $VHDImage


=========

OLD INFO:

bcdedit /copy '{current}' /d "entry_name"
bcdedit /set '{$guid}' device vhd=[C:]\Image.vhdx
bcdedit /set '{guid}' osdevice vhd=[C:]\Image.vhdx
bcdedit /set '{guid}' detecthal on

set default new entry to boot:
bcdedit /default '{guid}'

References:
http://technet.microsoft.com/en-us/library/dd799299(v=ws.10).aspx
https://github.com/rbellamy/WindowsPowerShell/blob/0281682ced5bedc17f1b3e9c1435e5d9e8b8f444/Scripts/add-bcd-vhd.ps1