MBR2GPT: Converting MBR to GPT Disk in Windows 10

Mbr2gpt.exe is a brand new built-in Windows 10 console instrument that permits you to convert a disk with the MBR (Master Boot Record) partition desk to a GPT (GUID Partition Table) with out information loss and with out the necessity to delete present partition. The mbr2gpt instrument can be utilized to convert the partition desk each in Windows PE (Windows Preinstallation Environment) and instantly from the working Windows 10. You can use this instrument to change the partition desk from MBR to GPT each on the information (non system) disk and on the system disk, on which Windows 10 is put in (utilizing the /allowFullOS possibility).

How does the MBR2GPT Tool Work?

The mbr2gpt.exe instrument is a part of the Windows 10 picture, ranging from construct 1703 (Creators Update). You can use mbr2gpt to convert a disk from MBR to GPT in offline mode on earlier Windows 10 builds (1507, 1511 and 1607). Previous Windows variations (Win 7/eight.1) should not formally supported.

Note. Earlier, a third-party instrument might be used to convert a non-system disk from MBR to GPT with out dropping present partitions. But to convert a system disk, you had to utterly clear up the disk, create GPT partition desk and new partitions on it, after which carry out a clear set up of Windows 10.

The MBR2GPT documentation says, that the next situations should be met to convert a disk partition desk to GPT:

  • Current disk partition desk is MBR;
  • There is free area on the disk for putting the first and secondary GPT tables at first and finish of the disk;
  • The MBR desk ought to comprise not more than three partitions, one among which is energetic (further and logical partitions needs to be lacking);
  • The should have a boot report pointing to a Windows partition.

The logic of Mbr2gpt when changing an MBR disk to a GPT is as follows:

  1. Disk examine;
  2. If there isn’t a EFI (ESP) system partition, it’s created utilizing free area from one of many partitions (if there’s not sufficient free area, an error message will seem “can't discover room for the EFI system partition”);
  3. UEFI boot recordsdata are copied to the EFI partition;
  4. GPT metadata and partition desk are utilized to the disk (the MBR partition desk is transformed to GPT with out dropping information on present partitions);
  5. The BCD bootloader configuration is up to date.

The syntax of the MBR2GPT instrument is:

mbr2gpt /validate|convert [/disk:] [/logs:] [/map:=] [/allowFullOS]

  • /validate– the disk is barely validated if the partition desk could be transformed (together with the examine of free area to retailer the first and the secondary GPT desk: 16 KB + 2 sectors in the start of the disk and 16 KB + 1 sector in the top);
  • /convert– begins changing the disk if the validation has been profitable;
  • /disk:— specifies the variety of the disk to be transformed into GPT. If the quantity shouldn’t be set, the system disk shall be transformed (like Diskpart command: choose disk system)
  • /logs:— specifies the trail to the listing the place MBR2GPT ought to write log recordsdata. If the trail shouldn’t be set, the %windir% folder is used. The log recordsdata are diagerr.xml, diagwrn.xml, setuperr.log and setupact.log;
  • /map:— permits you to specify further partition desk mappings between MBR and GPT. For instance, /map:42=. The variety of the MBR partition is specified in decimal notation, and GPT GUID accommodates delimiters. You can specify a number of mappings without delay;
  • /allowFullOS– by default, the MBR2GPT can be utilized solely in Windows PE. You can use the allowFullOS parameter in order to convert system disk instantly from working Windows 10.  Using this key, you may run the instrument in the complete Windows surroundings. If you don’t specify this parameter when utilizing mbr2gpt from Windows, an error will seem: ERROR: MBR2GPT can solely be used from the Windows Preinstallation Environment. Use /allowFullOS to override.

Convert Disk from MBR to GPT with out Dara Loss from Windows 10

The disk conversion operation from the MBR to GPT is irreversible. Make certain your pc helps UEFI earlier than changing.

Before changing the disk partition desk, let’s validate the present system disk for conversion from MBR to GPT:

mbr2gpt.exe /disk:zero /validate /Logs:C:logs /allowFullOS

MBR2GPT: Attempting to validate disk zero
MBR2GPT: Retrieving structure of disk
MBR2GPT: Validating structure, disk sector dimension is: 512

The line MBR2GPT: Validation accomplished efficiently reveals that this disk could be transformed. The line MBR2GPT: Disk structure validation failed implies that the disk can’t be transformed, as a result of it doesn’t fulfill the situations.

Another frequent error Cannot discover OS partition (s) for disk zero is most frequently related to the usage of a third-party bootloader or selecting a mistaken disk to convert. You also can attempt to transfer the Windows boot recordsdata to the system partition (bcdboot c:Windows /f bios /s c:), and examine the entries for the WinRE surroundings in the BCD (reagentc /disable && reagentc /allow) are right.

Tip. If the system disk is encrypted utilizing BitLocker, decrypt it earlier than conversion.

Now you may convert the partition desk on the system disk:

mbr2gpt.exe /convert /disk:zero

MBR2GPT will now try to convert disk zero.
If conversion is profitable the disk can solely be booted in GPT mode.
These adjustments can't be undone!
MBR2GPT: Attempting to convert disk zero
MBR2GPT: Retrieving structure of disk
MBR2GPT: Validating structure, disk sector dimension is: 512 bytes
MBR2GPT: Trying to shrink the system partition
MBR2GPT: Trying to shrink the OS partition
MBR2GPT: Creating the EFI system partition
MBR2GPT: Installing the brand new boot recordsdata
MBR2GPT: Performing the structure conversion
MBR2GPT: Migrating default boot entry
MBR2GPT: Adding restoration boot entry
MBR2GPT: Fixing drive letter mapping
MBR2GPT: Conversion accomplished efficiently
MBR2GPT: Before the brand new system can boot correctly you want to change the firmware to boot to UEFI mode!

Converting a disk from MBR to GPT from put in Windows 10 is finished in seconds.

To make a pc boot from the brand new EFI partition, you’ve got to change its settings to boot in the UEFI mode. Restart your pc and in the UEFI settings change the boot mode from Legacy (BIOS) to UEFI (Pure) and save the adjustments.

Windows 10 ought to boot efficiently. Using msinfo32.exe you may guarantee that Windows 10 has booted in the BIOS Mode = UEFI.

Key advantages of transferring to native UEFI mode and GPT partition desk:

  • You can create a partition bigger than 2 Tb dimension;
  • Protection of the boot surroundings with Secure Boot;
  • ELAM (Early Launch Antimalware) technology;
  • Device Guard and  options in Windows 10 Enterprise;
  • Measured Boot

Converting MBR to GPT throughout Windows 10 Installation

You can use the mbr2gpt instruments throughout Windows 10 set up. For instance, you , and are attempting to set up Windows 10 on a disk with an MBR partition desk on a UEFI-based pc. In this case, an error will seem:

Windows can't be put in to this disk. The chosen disk has an MBR partition desk. On EFI system, Windows can solely be put in to GPT disks.

If you don’t need to lose present information partitions on the MBR disk (it was used to boot in Legacy mode or on a pc with BIOS) when altering disk partition desk to GPT, you may convert the MBR disk to GPT instantly from the Windows 10 set up window.

  1. Press the keys Shift+F10 on the Windows 10 setup display screen to open the command immediate of the WinPE surroundings;
  2. Check if the disk partition desk could be transformed to GPT. Run the command: mbr2gpt /validate
  3. If the command returned Validation accomplished profitable, you may convert this disk;

    If the error Failed to retrieve geometry for disk -1 seems, most probably you’ve got a number of disks related to your pc. Run the command diskpart -> listing disk in order to establish disk numbers. You can validate a particular disk by the disk quantity with the command: mbr2gpt /validate /disk:zero

  4. To convert a disk partition desk run the command mbr2gpt /convert or with the disk quantity mbr2gpt /convert /disk:zero
  5. The mbr2gpt instrument will create a brand new , copy the Windows bootloader to it and convert the partition desk to GPT (present partitions shall be saved). You simply have to change to the Windows 10 Setup window, click on the Refresh button in the disk choice display screen and begin putting in Windows 10 on the chosen partition.

MBR2GPT Known Issues

After changing the partition desk utilizing mbr2gpt, most frequently there are issues with BitLocker and Hyper-V (accessible in Pro and Enterprise Windows 10 editions).

If you transformed you system disk and making an attempt to allow BitLocker, you might obtain an error message: The system can't discover the file specified. This is most probably the issue with the .

Try to rename the file %windirpercentSystem32RecoveryReAgent.xml and allow the BitLocker (a brand new ReAgent.xml file shall be created routinely).

There may be an error when beginning Hyper-V digital machines:

Virtual machine couldn't be began as a result of the hypervisor shouldn't be working.

To repair this error, you want to allow Hyper-V autostart in the BCD configuration:

BCDEDIT /Set hypervisorlaunchtype auto

If you attempt to convert disks with earlier Windows variations (7/eight.1), the instrument will give the error mbr2gpt can't set up new boot recordsdata. In this case, it is strongly recommended that you simply carry out in-place improve to Windows 10 first and solely then convert the partition desk.

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