MBR disk restore to UEFI system fails with "OS disk in backup uses MBR disk" warning

KB ID:
3156
Product:
Veeam Agent for Microsoft Windows
Version:
2.x, 3.x, 4.x
Published:
Last Modified:
2020-04-27

Challenge

When booting, the Veeam Agent machine fails to detect the operating system. You may see the following error message:

OS disk in backup uses MBR disk. This may cause boot issues on UEFI systems

Cause

Due to compatibility issues between certain BIOS versions and disk formats, Windows may not boot as the OS fails to detect the necessary boot files.

Solution

If your machine supports the legacy BIOS mode, use the legacy BIOS mode instead of the UEFI mode. If you machine does not support the legacy BIOS mode, do the following:

  1. Boot from the Veeam Recovery Media.
  2. Go to Tools and start the Command Prompt utility.
  3. Run the following commands one by one:
    C:\Users\administrator\diskpart
    DISKPART> list disk
    At this step, find the disk that you are going to use as a restore destination for the primary operating system. In this example, we assume that disk 0 is a restore destination for the primary operating system.
    DISKPART> select disk 0
    Mind that the following command will remove all data from the disk 0.
    DISKPART> clean 
    DISKPART> convert gpt
    DISKPART> create partition efi size=200
    DISKPART> select partition 1
    DISKPART> format quick fs=fat32 label="System"
    DISKPART> assign letter=G
    DISKPART> create partition msr size=128
    DISKPART> exit
  4. Start the restore process in the Manual restore mode. Do not restore the system partition and do not delete the partitions created at the previous step. Mind that you will see the "OS disk in backup uses MBR disk" warning during the restore process.
  5. After the restore process completes, do not reboot the Veeam Agent machine.
  6. Go to Tools > Command Prompt utility and run the following commands: 
    C:\Users\administrator\mkdir G:\EFI\Microsoft\Boot
    C:\Users\administrator\xcopy /s C:\Windows\Boot\EFI\*.* G:\EFI\Microsoft\Boot
    C:\Users\administrator\G:
    C:\Users\administrator\cd G:\EFI\Microsoft\Boot
    C:\Users\administrator\bootrec /rebuildbcd

More Information

To learn about restoring a GPT disk to the incompatible legacy BIOS system, see this Veeam KB article.

Please be aware that we’re making changes which will restrict access to product updates for users without an active contract.

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