Repairing EFI/GPT Bootloader using the DISKPART and BCDEdit command

Resources

This guide helps repair bootloader issues, for example getting a blue screen of death with the following error:

The boot configuration data for your PC is missing or contains errors.

c.f. http://woshub.com/how-to-repair-uefi-bootloader-in-windows-8/ for more background information.

Use diskpart to make System partition available.

(This will allow us to use bcdedit later in this guide to repair the bootloader.)

Boot from the Windows installation media

When at the Install Windows screen hit Shift+F10 to bring up a command prompt.

Type diskpart, then type list disk:

DISKPART> list disk

Disk #### Status Size Free Dyn Gpt

-------- ------------- ------- ------- --- ---

Disk 0 Online 465 GB 1024 KB *

Disk 1 Online 14 GB 0 B

Disk 2 Online 7695 MB 0 B

Select boot disk

You need to "Select" a disk before continuing. If only one disk shows, type, select disk 0. If there is more than one disk, they will need to verify based on disk size. If it is not disk 0 they would replace 0 with the number of the drive. (In my sample above, it is hopefully clear that '0' is the boot drive and the other two are not.)

DISKPART> select disk 0

Disk 0 is now the selected disk.

Verify Partitions

Type, list par, to verify that there are 4 partitions, Recovery, System, Reserved, Primary.

DISKPART> list par

Partition #### Type Size Offset

------------- ---------------- ------- -------

Partition 1 Recovery 450 MB 1024 KB

Partition 2 System 99 MB 451 MB

Partition 3 Reserved 16 MB 550 MB

Partition 4 Primary 464 GB 566 MB

Partition 5 Recovery 847 MB 464 GB

.

Select volume to use

Type, list vol, the volume number they want to use in the next step will have a FAT32 file system and should be 99MB with System under info.

DISKPART> list vol

Volume #### Ltr Label Fs Type Size Status Info

---------- --- ----------- ----- ---------- ------- --------- --------

Volume 0 C NTFS Partition 464 GB Healthy Boot

Volume 1 Recovery NTFS Partition 450 MB Healthy Hidden

Volume 2 FAT32 Partition 99 MB Healthy System

Volume 3 NTFS Partition 847 MB Healthy Hidden

Volume 4 F FAT32 Removable 14 GB Healthy

Volume 5 E IRON MAN FAT32 Removable 7695 MB Healthy

In this example, this is Volume 2.

Type, select vol 2, (number identified from previous step), i.e. select vol 2

DISKPART> select vol 2

Volume 2 is the selected volume.

Type, assign letter=z and should see "Diskpart successfully assigned the drive letter".

DISKPART> assign letter=z

DiskPart successfully assigned the drive letter or mount point.

Type exit (Z: drive is now the System partition)

Set up EFI boot partition using bcdedit (Boot Configuration Data editor)

(c.f. https://neosmart.net/wiki/bcdedit/#Commands_and_parameters for more info on bcdedit)

1. Type mkdir Z:\EFI\Microsoft\Boot
2. Type xcopy /s C:\Windows\Boot\EFI*.* Z:\EFI\Microsoft\Boot
3. Type z:
4. Type cd EFI\Microsoft\Boot
5. Type the following commands
   1. bcdedit /createstore BCD
   2. bcdedit /store BCD /create {bootmgr} /d "Windows Boot Manager"
   3. bcdedit /store BCD /create /d "My Windows 10" /application osloader (they can change My Windows 10 to anything they want)

The last command will return a GUID, for example, {D91FE7C2-605F-4A2B-B035-80A7C30979BF}, they will need to use this guid in the next step

1. Type the following commands
   1. bcdedit /store BCD /set {bootmgr} default {your_guid} (your_guid will be the guid mentioned in step 9)
   2. bcdedit /store BCD /set {bootmgr} path \EFI\Microsoft\Boot\bootmgfw.efi
   3. bcdedit /store BCD /set {bootmgr} displayorder {default}
   4. bcdedit /store BCD /set {default} device partition=c:
   5. bcdedit /store BCD /set {default} osdevice partition=c:
   6. bcdedit /store BCD /set {default} path \Windows\System32\winload.efi
   7. bcdedit /store BCD /set {default} systemroot \Windows
   8. exit
2. Reboot the machine.

Last Update: November 24, 2020