Move EFI partition when there is no space left

Over the years, after several moves to Linux and back, my home PC ended with the following awkward partitions on its two SSDs (all data is on NAS)

Disk1: [--- EFI partition 32MB ---][--- Empty ---]
Disk2: [--- Disk C: ---][--- OEM Partitition 450 MB ---]

Now I want to remove disk 1 from PC. The problem is EFI partition. Is it possible to reduce OEM Partition od disk 2 and put EFI partition in its place? How to restore bootloader in the new place?

I have Linux LiveUSBs at hand to move partitions externally, but I am curious if Windows can do it on its own. I don't want to move whole C: partition, it will take whole evening even on SSD.

Barafu Albino

Posted 2018-09-02T16:20:15.077

Reputation: 245

1OEM partition isn’t required for the system to boot the EFI partition is required. The OEM partition can easily be created again. As always proper backups are required before any changes to your partitions – Ramhound – 2018-09-02T17:53:42.460

1OEM usually contains backups of proprietary drivers and bloatware, such as trial games. If you've imaged the disk, as @Ramhound states, you can recreate it if you want to sell the PC is "as new" shape. – DrMoishe Pippik – 2018-09-02T19:12:50.187

It would be simpler to reduce partition C so as to make a little space and copy there the EFI. The only limit found in the specs is that the EFI must reside in the first 2.2 Terabytes. But keep a disk image backup, just in case. – harrymc – 2018-09-02T20:05:39.857

Those drivers are often extremely outdated. Which is the reason the partitions shouldn't be kept. They are simply a waste of space.. – Ramhound – 2018-09-03T01:59:49.633

Answers

If Disk2 is partitioned using MBR, then you can use mbr2gpt.exe on it provided you are running Windows v1703 or later and it will create the EFI partition for you on Disk2:

1) mbr2gpt.exe /validate /disk:2 /allowFullOS

If this fails for you with an error about no OS found it's because you are using UEFI in legacy mode to boot the Windows installation from MBR, and the mbr2gpt.exe expects you to be booting in BIOS (it needs you to have a /boot folder with the BCD store in it, but UEFI systems have an EFI folder instead), so run this to create the BCD file but before you run this make sure to give your OEM partition a letter as we need to place the boot files there so mbr2gpt can do it's conversion:

2) bcdboot c:\Windows /s LetterOfOEMPartition: /f bios

If 1) didn't fail for you then just run this:

3) mbr2gpt.exe /convert /disk:2 /allowFullOS

After that you can wipe the original EFI partition from Disk1 using diskpart delete with an override switch, and you can delete the OEM partition from disk 2 using the same method. The EFI partition on Disk2 will be all that's required to boot your C:\windows.

If Disk2 is partitioned using GPT, then you just have to delete the OEM partition and replace it with this using diskpart: 1) create partition efi size=100 2) format quick fs=fat32 3) assign letter=s

and then exit, and run this final command to create the boot files on the new EFI partition: 4) bcdboot C:\windows /s S:

ZEM

Posted 2018-09-02T16:20:15.077

Reputation: 11

Move EFI partition when there is no space left - may I remove OEM Partition?

Answers