Installing Multiple EFI Partitions Without Disconnecting Installed Drives

Please **do not move** this question to SuperUser. My question relates to EFI partition manipulation, which is not inherent to Windows. ## Background ## I ran into an issue with UEFI and OS Versions, and I would like some help. By no means is this an advertisement for my OEM, or a preference for OS'es, but I'm using them to give a thorough description of the issue. Recently, I found Xidax , an OEM builder for gaming systems. I also use the system they built for Linux and OS experimentation, besides the gaming. I used to build my own, but age and disability have severely hampered my hand strength and my patience, which is where this issue starts. ## Issue ## My System is built with a MSI motherboard supporting UEFI, SecureBoot, etc. (fairly recently built). I've replaced the stock MS Windows UEFI loader with rEFInd . This EFI boot manager allows me to boot the following OS'es, all on Different Drives: 1. Windows 11 M2 - 1TB (also where the EFI partition is) 2. Gentoo Linux 3. FreeBSD 12 or 13 (which I removed because I hadn't touched or updated it in ages) Having removed #3, I now have an empty drive (8TB in size), and decided to try something I'd never done. I have installed Windows 11 on the empty 8TB in hopes of "converting it" into the current AtlasOS . The Windows Installer correctly found the EFI Partition on my M2 Drive and added the Entry to the Windows Loader(WinLoad.efi). I now have a boot menu based on winloader(the white and blue screen) with 2 choices for Widows 11. ## Side By Side versions of Linux ## Forgetting for a moment that this is Windows and remembering I cannot disconnect the First Install to trick the second install into building an EFI partition (due to disability) on the second drive, and using the following scenario: 1. Replace the Word Windows above with a Linux Distribution - For the sake of this example I'll choose Ubuntu 2. Install Ubuntu grub version X copy 1 into the only EFI partition 3. Install Ubuntu grub version X copy 2 into the only EFI partition Now realizing that I've clobbered the First Installs grub with the second because there is only one ubuntu folder in the EFI partition, I'm stuck as I would like to access both copies independently of each other. For an example of the type of fix I need to implement in a different way, see In rEFInd, need 2 different OS icons for 2 instances of same OS (Ubuntu-MATE) . To do this for Windows/rEFInd, I started with: Booting Multiple Windows Installations from a Third-Party Boot Manager . If you look at the "7 Getting into Windows Went..." steps that is exactly what I have to do to get to either version until I get this fixed. I'm trying to do this with only 1 EFI Partition, before I use the second answer in Installing rEFInd on Dual Boot Windows 10 Machine (See why I don't want it moved now?). I'd rather not have EFI partitions all over my drives if I can help it. ## Attempted Fix ## 1. From a Windows Command Prompt, issued mountvol b: /s. - That worked, I did that the first time I installed rEFInd without access to my Gentoo Install 2. mkdir b:\EFI\Win10 and mkdir b:\EFI\AtlasOS. - Worked again, but darn their empty and I sure don't want to screw up my EFI partition. 3. First xcopy /s b:\EFI\Microsoft\Boot b:\EFI\win10 - Well *shoot*, that failed with Sharing Violation. What?!?! Wait, didn't I run the prompt as Administrator, and isn't my account in the Administrators Group... checking... yes Oh wait Microsoft thinks I'm stupid for wanting to alter the EFI manually on a machine that I OWN. But wait, I can edit it in my Gentoo install so: 4. Rebooted into Gentoo 5. Mounted boot 6. Opened gparted because I never can remember the /dev name for the EFI partition 7. Mounted the EFI partition to /boot/efi 8. Cded to /boot/efi/EFI/Microsoft/Boot 9. Issued cp -xa . /boot/EFI/Win10 and the same for AtlasOS 10. Reinstalled grub as I had to boot the kernel directly from rEFInd. Now I'm finally to the step to alter the BCD, whew back to Windows. By that time it was 12:30AM last night, and I need sleep, so I decided to come here and ask for advice/help. ## Questions ## As I said, I'd rather have 1 EFI partition so I'd like to modify that Fix a bit by asking the following: 1. What are the barebones essentials that need to be in /boot/efi/EFI/{Win10,AltlasOS} in order for the boot to occur cleanly? - cp -xa did in fact replicate xcopy but when I rebooted to start on the BCD I noticed all kinds of files etc. listed on rEFInd's menu. I don't want to have to hide them all when there are possibly hundreds. 2. Is there an easier way to split the entries up than the approach I've chosen? 3. How do I treat an update to the EFI partition in the Future, i.e., will the manual adds need to be readded if Windows Update decides to push an update to the EFI/BCD?