Dualboot-Installations fails for boot to Windows 10 after running fai

Hello,

perhaps there is someone out there, having solved the following problem:

I do have a oem-installed Windows 10 Pro (Dell PC) and would like to 
install (using FAI) a Linux as parallel boot.

That works, up to that point, that Windows isn't bootable after running 
fai. Windows bootloader shows with blue screen claiming a missing 
bootdevice.

After using a windows-boot-stick with commandline and typing:

bcdedit /set {default} osdevice partition=C:

bcdedit /set {default} device partition=C:

everything is fine again and windows is able to boot again.

At first I thought the problem is the resizing of C: using ntfsresize in 
FAI. So I changed to run a diskpart script in Windows before, which 
shrinks the C-Drive and creates to partitions without formatting. So I 
ended up using the following diskconfig:

disk_config sda preserve_always:1,2 disklabel:gpt bootable:1 fstabkey:label
primary /boot/efi       99MB:preserve_always    vfat rw
primary -       128MiB:preserve_always  - -
primary -       400GiB:preserve_always  - -
primary swap    16GiB   swap    sw
primary /       50GiB   ext4    rw,noatime,errors=remount-ro 
createopts="-L ROOT"
primary -       8GiB-:preserve_lazy     ntfs    - createopts="-L DATEN"

the 400GiB partition is the ntfs-formatted C-Drive. The first tried 
solution was using:

disk_config sda preserve_always:1,2 disklabel:gpt bootable:1 fstabkey:label
primary /boot/efi       99MB:preserve_always    vfat rw
primary -       128MiB:preserve_always  - -
primary -       400GiB:resize  ntfs -
primary swap    16GiB   swap    sw
primary /       50GiB   ext4    rw,noatime,errors=remount-ro 
createopts="-L ROOT"
primary -       8GiB-:preserve_lazy     ntfs    - createopts="-L DATEN"

What does setup-storage do (or the used programs behind that tool), that 
the windows-bootloader can't find the C: partition after using fai?

Thanks for any input... If I didn't find the solution I have to boot 140 
PCs with Windows-USB-Stick to type the bcdedit lines mentioned above...


Sven


-- 
Sven Schumacher                       Tel: (0511)762-2753
Leibniz Universitaet Hannover
Fakultät für Maschinenbau, Head of Systemadministration
An der Universität 1 - 30823 Garbsen

Institut für Turbomaschinen und Fluid-Dynamik       - TFD
Institut für Kraftwerkstechnik und Wärmeübertragung - IKW
Institut für Technische Verbrennung                 - ITV