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Fix: Rebuild Windows EFI

Rebuilding the Windows EFI partition, dual-boot with systemd-boot on a seperate drive

If I had a dollar for every time that I somehow overwrote or deleted the Windows EFI boot partiton while toying with something on Linux I’d have $3 (which isn’t a lot but having it happen 3 times already is pretty annoying). If you ask some enthusiasts, this is secretly a blessing in disguise since you’re technically one step closer to escaping the grasp of Microsoft. However like many others who choose to dual-boot, I prefer to keep my Windows installation around in case I need it for some specific use case.

I’m not the most well-versed when it comes to the whole Windows IT stuff, in fact I think most of my knowledge about how to even use the Windows shell has completely gone out the Window. This post serves as a quick guide for how to rebuild the EFI partition that contains the bootloader, as well as how to re-add the Windows to the systemd-boot menu.

Diagnosis

Depending on the order in which you installed Windows and Linux, the location of where your EFI partition actually is may differ. On my setup, I have Windows on my first drive and Linux on my second. My EFI partition with my current bootloader lives on my second drive which persumably also included my Windows 11 bootloader.

So when I went and installed a different distro, this removed all my files associated about my previous install (since I basically reformatted everything), and among that of course was the Windows bootloader meaning I effectively had no way to boot back into Windows

Chances are that if you find that the Windows boot option is missing, you’re in the same boat.

Rebuild the EFI Partition

  1. Flash the Live Media ISO to a USB Use Balena Etcher or something similar to flash the Disk Image ISO to a USB drive.

  2. Reboot into the Live USB For some reason you have to press something (literately any key) on your keyboard after selecting to boot into the media, or else it’ll just kick you back into the UEFI menu.

  3. Select Repair Your Computer and Advanced Options. Launch the Command Prompt

Launch the diskpart utility

diskpart

Select the disk with Windows on it:

select disk X

It helps to list the disks and examine the partitions to differentiate between them. Usually if there’s 20gb or so Recovery/Reserved partition that’ll be a pretty good indicator of the drive Windows was installed on

list disk
select disk X
list part

Make sure you’ve selected the disk with Windows on it!

  1. Shrink a partition for the new EFI I’d suggest shrinking the partition that holds your current Windows files. Usually it’ll have the type Primary.

It’ll look something like that’s below

Partition ### Type     Size    Offset
------------- -------- ------- ------
Partition 1   Primary  200 GB   18 KB
Partition 2   Reserved 20 GB    17 KB

Select the partition you want to shrink from. (or don’t if you have 500MB of freespace somehow)

select part X

Then shrink it

shrink desired=500
  1. Create the EFI partition The drive letter can be whatever you want, as long as its not already in use (Y is a good one)
create partition efi
format fs=fat32 quick
assign letter=Y

Exit diskpart with

exit
  1. Install the bootloader The drive letter below Y will be replaced with whatever letter you chose in the last step
bcdboot c:\Windows /s Y: /f ALL

Now reboot and see if you can get into Windows

Re-add Windows to systemd-boot

Ok assuming you can get into Windows, we want to re-add the option for Windows into systemd-boot.

Go ahead and boot into Linux and locate the newly created EFI partition

lsblk -f

Look for something that’s vfat FAT32

There should be 1 on each drive, go ahead and note the names of these 2 down, as well as which one is for which OS

Example: (the name is the first column of the output)
nvme0n1p1
nvme1n1p1
  1. Mount the EFI partitions First create the mount points for both partitions
sudo mkdir /mnt/arch_efi
sudo mkdir /mnt/efi

You can name them whatever, but I’ll use the name arch_efi for the Linux EFI partition and efi for the Windows partition

Mount both partitions

sudo mount /dev/your_drive_name_linux /mnt/arch_efi
sudo mount /dev/your_drive_name_windows /mnt/efi
  1. Find the Microsoft folder in Windows EFI You can also open Dolphin or whatever file manager as root if it helps
cd /mnt/efi
ls

There should be a folder named EFI, and inside it there should be a Microsoft folder

Once you have confirmed this, go ahead and copy this folder over to the EFI folder in /mnt/arch_efi

sudo cp -r /mnt/efi/EFI/Microsoft /mnt/arch_efi/EFI/

Unmount everything

sudo umount /mnt/efi
sudo umount /mnt/arch_efi
  1. Update systemd-boot configuration
sudo bootctl update

This is usually done automatically though

Now go ahead and reboot and you should see the Windows option in systemd-boot again.