Posted on November 9, 2017 · Posted in Windows 10

How to Rebuild BCD File in Windows 10

The Boot Manager in the modern Windows versions uses the BCD (Boot Configuration Data) file to boot the operating systems. This file contains information about the installed OSs on the computer and their boot parameters. If the BCD file is deleted or corrupted, Windows stops to be booted. In this article, we’ll show how to rebuild Boot Configuration Data file manually in Windows 10.

If the BCD file is missing or damaged, a user is likely to see the following message when trying to boot Windows:

Your PC needs to be repaired
The Boot Configuration Data file is missing some required information
File: \Boot\BCD
Error code: 0xc0000034

The Boot Configuration Data file is missing some required information

If this error appears, first of all try to fix the problem with booting the OS using Startup Repair mode that can be started from Windows Recovery Environment (Windows RE).

Tip. It is advisable to periodically check the health of the WinRE environment,, and if it doesn’t work, use the method described in the article How to Recover WinRE in Windows 10 to recover it.

If the automatic repair using Startup Repair did not help, boot from Windows boot/installation disk or use WinRE (Repair your computer -> Troubleshoot  -> Advanced options -> Command Prompt). Start the command prompt and try to create a new BCD file from scratch.

Windows Recovery Environment - run Command Prompt

Very important. All instructions given below are suitable for standard BIOS with MBR systems. In a UEFI system, you need to use the following instruction to repair the bootloader in Windows 10/8 with EFI or in Windows 7.

In this example, I will use Windows 10 installation disk. After booting from it, press Shift+F10 on the language selection screen.

Try to restore the BCD file automatically using this command:

bootrec /RebuildBCD

Reboot your computer and check if Windows boots. If it isn’t, boot from the installation disk again and start the command prompt. You need have to identify the drives of the system. (It is likely that the volume letters assigned to them will be different from those you see when working in Windows). It is easier to do it using diskpart. Run these commands:

diskpart
list vol

diskpart - reserved partition

You will see the list of partitions, the drive letters assigned to them and their sizes. In our case, there are only two partitions in the system:

  • System Reserved partition with the size of 500 MB and the letter C: assigned to it. By default, BCD file is located in this little service partition (read more)
  • NTFS partition with the size of 39 GB and the letter D: assigned to it. This partition contains the Window and user data

Important. Remember the assigned drive letters, since they will be used in the commands later.

Using the following commands, we’ll make the necessary links to Windows bootloader appear inthe  MBR and in the boot sector.

bootrec.exe /fixmbr
bootsect.exe /nt60 all /force

Tip.If bootsect.exe is not found, try to specify this path:
X:\boot\bootsect.exe /nt60 all /force

bootsect.exe /nt60 all /force

Then using BCDedit command, create a new Boot Configuration Data file (it is supposed, you don’t have the BCD backup).

Delete the old (corrupted) BCD file in System Reserved partition and create a new one instead.
del c:\boot\bcd

Create an empty temporary file bcd.tmp
bcdedit /createstore c:\boot\bcd.tmp

Create an entry for the Boot Manager (bootmgr)
bcdedit.exe /store c:\boot\bcd.tmp /create {bootmgr} /d "Windows Boot Manager"

Import settings from bcd.tmp to your BCD
bcdedit.exe /import c:\boot\bcd.tmp

Specify that the Boot Manager is located in System Reserved partition (the letter C: is assigned to it)
bcdedit.exe /set {bootmgr} device partition=c:

Configure the timeout to select an OS
bcdedit.exe /timeout 10

Delete the temporary file
del c:\boot\bcd.tmp

recreating bcd in windows 10 using bcdedit

So we have a file with the bootloader parameters. Now you have to add the entries about the OSs available on the computer.
Create a new entry for Windows 10 in the BCD repository
bcdedit.exe /create /d "Windows 10" /application osloader

The command will return the unique identificator (GUID) of this bootloader entry.
The entry {8a7f03d0-5338-11e7-b495-c7fffbb9ccfs} was successfully created.

bcdedit - The entry was successfully created.

Specify that bootmgr must use this entry by default (after the timeout, this entry is used to boot).

bcdedit /default {8a7f03d0-5338-11e7-b495-c7fffbb9ccfs}

Now you have to specify the paths to the installed Windows copy on the hard disk in the new bootloader entry. (We have seen in WinPE that the letter D: is assigned to Windows partition.)

bcdedit.exe /set {default}device partition=d:
bcdedit.exe /set {default} osdevice partition=d:
bcdedit.exe /set {default} path \Windows\system32\winload.exe
bcdedit.exe /set {default} systemroot \Windows

Make this entry visible, since it is hidden by default
bcdedit.exe /displayorder {default} /addlast

bcdedit.exe /displayorder {default} /addlast

So we have rebuilt Boot Configuration Data. Now you can restart your computer and make sure that Windows 10 boots as usual.

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