How to change a disk GUID


johnpd

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I went through the process of expanding the EFI partition on my system. However it appears that the new EFI partition got its own GUID. Is there way to assign it back to what everything else on the drive is assigned?

JohnD
 

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I went through the process of expanding the EFI partition

Exactly how and what program did you use to do that.
Please post a screenshot of disk management.
 

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I used Disk Management to shrink the C: drive, then diskpart to format that shrunk area as new EFI and deleted the old EFI.
 

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Run diskpart:
Code:
select disk 0
select part [N]
set id=c12a7328-f81f-11d2-ba4b-00a0c93ec93b

Should I be afraid of asking how you copied the old EFI's contents over?
 

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You can not move the efi partition to another location on the disk nor can you resize it in disk management. You have to use 3d party tool like Minitool Partition Wizard, Aoemi Partition Assistant, or Disk Genius to resize each partition to the right until there is unallocated space directly adjacent to the EFI patition. You then extend the EFI partition into the unallocated space. Am I right on that @garlin?
 

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bcdboot C:\Windows /s T: where T was the letter I assigned to it.

The problem I am running into is that Macrium Reflect is failing when it hits the EFI partition saying it does not exist. The backup copies the entire disk. The Windows partition, EFI partition, and recovery partition all had the same GUID. Now the EFI has a different GUID, but on other systems I have, that is not a problem. The script is using the new GUID. Let me check with Macrium to see what might be messed up.
 

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You can not move the efi partition to another location on the disk nor can you resize it in disk management. You have to use 3d party tool like Minitool Partition Wizard, Aoemi Partition Assistant, or Disk Genius to resize each partition to the right until there is unallocated space directly adjacent to the EFI patition. You then extend the EFI partition into the unallocated space. Am I right on that @garlin?
I am not resizing it in Disk Management. I took a small piece of the Windows partition using Disk Management and then used diskpart to reassign the EFI to that new partition and deleted the old EFI.
 

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I took a small piece of the Windows partition using Disk Management and then used diskpart to reassign the EFI to that new partition and deleted the old EFI.
But as Garlin asked , how did you get the data from the original EFI partition into the new partition you created? If I am not mistaken I believe the EFI partition is supposed to be the first partition on the drive.

Sure would like to see a screenshot of disk management with the columns expanded so we can see everything
 

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Here are Disk Mgmt and Partition Wizard displays. I have an older drive with the original Windows installation on it (256GB). The one I am currently using is 2TB.
 

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See if the computer is or is not able to boot with each bootable drive after detaching other drives with EFI partitions.


Run: diskparinfo > post a share link



 

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Never mind. I got it to run, but now I have a worse problem. When I get to the Desktop, it displays for a few seconds then disappears. I will start another thread.

JohnD
 

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@johnpd

Run a stand alone bootable version of Gparted. In the GUI there's an option to change the GUUID or assign one manually). If you want to re-set the GUUID back to what it was you will need to know it though. You could get that if you have an old image -- restore that, note the partition GUUID's, then restore the failing imge, boot Gparted and re-assign the Guuid's.

Note though in Gparted the partitions in the GUI will appear as /dev/xxx but the file type etc are shown clearly so the Windows partitions are easily seen.

E.g : On a dual boot disk (Linux and Windows) :

Screenshot_20251027_121757.webp

Cheers
jimbo
 

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bcdboot C:\Windows /s T: where T was the letter I assigned to it.

The problem I am running into is that Macrium Reflect is failing when it hits the EFI partition saying it does not exist. The backup copies the entire disk. The Windows partition, EFI partition, and recovery partition all had the same GUID. Now the EFI has a different GUID, but on other systems I have, that is not a problem. The script is using the new GUID. Let me check with Macrium to see what might be messed up.
bcdboot /s will copy the required boot files.

The reason for asking the question, in case there was other files tucked inside EFI that were installed by your OEM (firmware) or another tool.

It's not always the case. When any partition is designated EFI, the GUID is c12a7328-f81f-11d2-ba4b-00a0c93ec93b. Obviously you can only have one of that GUID per disk.
 

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I have resolved all my issues. The blank Desktop was caused by a bum program which apparently crashed Windows Explorer. I updated it and now the system is operating normally. Thanks to all who helped.
 

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You can not move the efi partition to another location on the disk nor can you resize it in disk management. You have to use 3d party tool like Minitool Partition Wizard, Aoemi Partition Assistant, or Disk Genius to resize each partition to the right until there is unallocated space directly adjacent to the EFI patition. You then extend the EFI partition into the unallocated space. Am I right on that @garlin?
I just make a backup of EFI with Macrium Reflect and restore to new location having freed up some space as required.
 

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The EFI partition is just a "normal" partition and can be anywhere on the disk. UEFI booting just reads the efi partition which is just a file.

Here I have 2 efi partitions - ome for grub for linux boot and the other (about 50% of the way through the disk) for Windows native boot. It's customary (but not mandatory) to have the efi partitions at the front of the rest of the data for the OS.

Here /dev/sda1 and /dev/sda4 are efi partitions -- /dev/sda1 for Linux Grub and /dev/sda4 for a Windows system.

Screenshot_20251027_222011.webp

Cheers
jimbo
 

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