Apa maksud no efi system partition

• Article
• 03/16/2022
• 15 minutes to read

Applies to

MBR2GPT.EXE converts a disk from the Master Boot Record (MBR) to the GUID Partition Table (GPT) partition style without modifying or deleting data on the disk. The tool is designed to be run from a Windows Preinstallation Environment (Windows PE) command prompt, but can also be run from the full Windows 10 operating system (OS) by using the /allowFullOS option.

MBR2GPT.EXE is located in the Windows\System32 directory on a computer running Windows 10 version 1703 (also known as the Creator's Update) or later.

The tool is available in both the full OS environment and Windows PE. To use this tool in a deployment task sequence with Configuration Manager or Microsoft Deployment Toolkit (MDT), you must first update the Windows PE image (winpe.wim, boot.wim) with the Windows ADK 1703, or a later version.

See the following video for a detailed description and demonstration of MBR2GPT.

You can use MBR2GPT to:

• Convert any attached MBR-formatted system disk to the GPT partition format. You cannot use the tool to convert non-system disks from MBR to GPT.
• Convert an MBR disk with BitLocker-encrypted volumes as long as protection has been suspended. To resume BitLocker after conversion, you will need to delete the existing protectors and recreate them.
• Convert operating system disks that have earlier versions of Windows 10 installed, such as versions 1507, 1511, and 1607. However, you must run the tool while booted into Windows 10 version 1703 or later, and perform an offline conversion.
• Convert an operating system disk from MBR to GPT using Configuration Manager or MDT provided that your task sequence uses Windows PE version 1703 or later.

Offline conversion of system disks with earlier versions of Windows installed, such as Windows 7, 8, or 8.1 are not officially supported. The recommended method to convert these disks is to upgrade the operating system to Windows 10 first, then perform the MBR to GPT conversion.

Important

After the disk has been converted to GPT partition style, the firmware must be reconfigured to boot in UEFI mode.

Make sure that your device supports UEFI before attempting to convert the disk.

Disk Prerequisites

Before any change to the disk is made, MBR2GPT validates the layout and geometry of the selected disk to ensure that:

• The disk is currently using MBR
• There is enough space not occupied by partitions to store the primary and secondary GPTs:
  • 16KB + 2 sectors at the front of the disk
  • 16KB + 1 sector at the end of the disk
• There are at most 3 primary partitions in the MBR partition table
• One of the partitions is set as active and is the system partition
• The disk does not have any extended/logical partition
• The BCD store on the system partition contains a default OS entry pointing to an OS partition
• The volume IDs can be retrieved for each volume which has a drive letter assigned
• All partitions on the disk are of MBR types recognized by Windows or has a mapping specified using the /map command-line option

If any of these checks fails, the conversion will not proceed and an error will be returned.

Syntax

MBR2GPT /validate|convert [/disk:<diskNumber>] [/logs:<logDirectory>] [/map:<source>=<destination>] [/allowFullOS]

Options

Examples

Validation example

In the following example, disk 0 is validated for conversion. Errors and warnings are logged to the default location, %windir%.

Conversion example

In the following example:

1. Using DiskPart, the current disk partition layout is displayed prior to conversion - three partitions are present on the MBR disk (disk 0): a system reserved partition, a Windows partition, and a recovery partition. A DVD-ROM is also present as volume 0.
2. The OS volume is selected, partitions are listed, and partition details are displayed for the OS partition. The MBR partition type is 07 corresponding to the installable file system (IFS) type.
3. The MBR2GPT tool is used to convert disk 0.
4. The DiskPart tool displays that disk 0 is now using the GPT format.
5. The new disk layout is displayed - four partitions are present on the GPT disk: three are identical to the previous partitions and one is the new EFI system partition (volume 3).
6. The OS volume is selected again, and detail displays that it has been converted to the GPT partition type of ebd0a0a2-b9e5-4433-87c0-68b6b72699c7 corresponding to the PARTITION_BASIC_DATA_GUID type.

As noted in the output from the MBR2GPT tool, you must make changes to the computer firmware so that the new EFI system partition will boot properly.

Specifications

Disk conversion workflow

The following steps illustrate high-level phases of the MBR-to-GPT conversion process:

1. Disk validation is performed.
2. The disk is repartitioned to create an EFI system partition (ESP) if one does not already exist.
3. UEFI boot files are installed to the ESP.
4. GPT metadata and layout information is applied.
5. The boot configuration data (BCD) store is updated.
6. Drive letter assignments are restored.

Creating an EFI system partition

For Windows to remain bootable after the conversion, an EFI system partition (ESP) must be in place. MBR2GPT creates the ESP using the following rules:

1. The existing MBR system partition is reused if it meets these requirements:

   1. It is not also the OS or Windows Recovery Environment partition.
   2. It is at least 100MB (or 260MB for 4K sector size disks) in size.
   3. It is less than or equal to 1GB in size. This is a safety precaution to ensure it is not a data partition.
   4. The conversion is not being performed from the full OS. In this case, the existing MBR system partition is in use and cannot be repurposed.

2. If the existing MBR system partition cannot be reused, a new ESP is created by shrinking the OS partition. This new partition has a size of 100MB (or 260MB for 4K sector size disks) and is formatted FAT32.

If the existing MBR system partition is not reused for the ESP, it is no longer used by the boot process after the conversion. Other partitions are not modified.

Important

If the existing MBR system partition is not reused for the ESP, it might be assigned a drive letter. If you do not wish to use this small partition, you must manually hide the drive letter.

Partition type mapping and partition attributes

Since GPT partitions use a different set of type IDs than MBR partitions, each partition on the converted disk must be assigned a new type ID. The partition type mapping follows these rules:

1. The ESP is always set to partition type PARTITION_SYSTEM_GUID (c12a7328-f81f-11d2-ba4b-00a0c93ec93b).
2. If an MBR partition is of a type that matches one of the entries specified in the /map switch, the specified GPT partition type ID is used.
3. If the MBR partition is of type 0x27, the partition is converted to a GPT partition of type PARTITION_MSFT_RECOVERY_GUID (de94bba4-06d1-4d40-a16a-bfd50179d6ac).
4. All other MBR partitions recognized by Windows are converted to GPT partitions of type PARTITION_BASIC_DATA_GUID (ebd0a0a2-b9e5-4433-87c0-68b6b72699c7).

In addition to applying the correct partition types, partitions of type PARTITION_MSFT_RECOVERY_GUID also have the following GPT attributes set:

• GPT_ATTRIBUTE_PLATFORM_REQUIRED (0x0000000000000001)
• GPT_BASIC_DATA_ATTRIBUTE_NO_DRIVE_LETTER (0x8000000000000000)

For more information about partition types, see:

• GPT partition types
• MBR partition types

Persisting drive letter assignments

The conversion tool will attempt to remap all drive letter assignment information contained in the registry that correspond to the volumes of the converted disk. If a drive letter assignment cannot be restored, an error will be displayed at the console and in the log, so that you can manually perform the correct assignment of the drive letter.

Important

This code runs after the layout conversion has taken place, so the operation cannot be undone at this stage.

The conversion tool will obtain volume unique ID data before and after the layout conversion, organizing this information into a lookup table. It will then iterate through all the entries in HKLM\SYSTEM\MountedDevices, and for each entry do the following:

1. Check if the unique ID corresponds to any of the unique IDs for any of the volumes that are part of the converted disk.
2. If found, set the value to be the new unique ID, obtained after the layout conversion.
3. If the new unique ID cannot be set and the value name starts with \DosDevices, issue a console and log warning about the need for manual intervention in properly restoring the drive letter assignment.

Troubleshooting

The tool will display status information in its output. Both validation and conversion are clear if any errors are encountered. For example, if one or more partitions do not translate properly, this is displayed and the conversion not performed. To view more detail about any errors that are encountered, see the associated log files.

Logs

Four log files are created by the MBR2GPT tool:

• diagerr.xml
• diagwrn.xml
• setupact.log
• setuperr.log

These files contain errors and warnings encountered during disk validation and conversion. Information in these files can be helpful in diagnosing problems with the tool. The setupact.log and setuperr.log files will have the most detailed information about disk layouts, processes, and other information pertaining to disk validation and conversion.

Note

The setupact*.log files are different than the Windows Setup files that are found in the %Windir%\Panther directory.

The default location for all these log files in Windows PE is %windir%.

Interactive help

To view a list of options available when using the tool, type mbr2gpt /?

The following text is displayed:

Return codes

MBR2GPT has the following associated return codes:

Determining the partition type

You can type the following command at a Windows PowerShell prompt to display the disk number and partition type. Example output is also shown:

You can also view the partition type of a disk by opening the Disk Management tool, right-clicking the disk number, clicking Properties, and then clicking the Volumes tab. See the following example:

If Windows PowerShell and Disk Management are not available, such as when you are using Windows PE, you can determine the partition type at a command prompt with the DiskPart tool. To determine the partition style from a command line, type diskpart and then type list disk. See the following example:

In this example, Disk 0 is formatted with the MBR partition style, and Disk 1 is formatted using GPT.

Known issue

MBR2GPT.exe cannot run in Windows PE

When you start a Windows 10, version 1903-based computer in the Windows Preinstallation Environment (Windows PE), you encounter the following issues:

Issue 1 When you run the MBR2GPT.exe command, the process exits without converting the drive.

Issue 2 When you manually run the MBR2GPT.exe command in a Command Prompt window, there is no output from the tool.

Issue 3 When MBR2GPT.exe runs inside an imaging process such as a Microsoft Endpoint Manager task sequence, an MDT task sequence, or by using a script, you receive the following exit code: 0xC0000135/3221225781.

Cause

This issue occurs because in Windows 10, version 1903 and later versions, MBR2GPT.exe requires access to the ReAgent.dll file. However, this dll file and its associated libraries are currently not included in the Windows PE boot image for Windows 10, version 1903 and later.

Workaround

To fix this issue, mount the Windows PE image (WIM), copy the missing file from the Windows 10, version 1903 Assessment and Development Kit (ADK) source, and then commit the changes to the WIM. To do this, follow these steps:

1. Mount the Windows PE WIM to a path (for example, C:\WinPE_Mount). For more information about how to mount WIM files, see Mount an image.

2. Copy the ReAgent files and the ReAgent localization files from the Windows 10, version 1903 ADK source folder to the mounted WIM.

   For example, if the ADK is installed to the default location of C:\Program Files (x86)\Windows Kits\10 and the Windows PE image is mounted to C:\WinPE_Mount, run the following commands from an elevated Command Prompt window:

   Note

   You can access the ReAgent files if you have installed the User State Migration Tool (USMT) as a feature while installing Windows Assessment and Deployment Kit.

   Command 1:

   copy "C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Windows Setup\amd64\Sources\ReAgent*.*" "C:\WinPE_Mount\Windows\System32"

   This command copies three files:

   • ReAgent.admx
   • ReAgent.dll
   • ReAgent.xml

   Command 2:

   copy "C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Windows Setup\amd64\Sources\En-Us\ReAgent*.*" "C:\WinPE_Mount\Windows\System32\En-Us"

   This command copies two files:

   • ReAgent.adml
   • ReAgent.dll.mui

   Note

   If you aren't using an English version of Windows, replace "En-Us" in the path with the appropriate string that represents the system language.

3. After you copy all the files, commit the changes and unmount the Windows PE WIM. MBR2GPT.exe now functions as expected in Windows PE. For information about how to unmount WIM files while committing changes, see Unmounting an image.

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