I recently installed Arch Linux in dual boot alongside an existing Windows 10 (Windows 10 was pre-installed on my Dell XPS 7590) in UEFI.

When it came to partitioning, I've created a 300MB partition for ESP (EFI System Partition). I installed the whole system, and I'm successfully able to boot (with Grub) to Arch or Windows 10.

However, there was already an ESP (probably created by the Windows 10 install) that I could have re-used instead of creating a new one. My NVME disk is now formatted like (I only kept the interesting details) :

/dev/nvme0n1p1 # Windows ESP
  └ EFI
    ├ Boot
    │ └ bootx64.efi
    └ Microsoft
      └ Boot
        └ bootmgfw.efi

/dev/nvme0n1p8 # Arch ESP
  └ EFI
    └ arch
      └ grubx64.efi

I've read that, even if it works, having 2 ESP on the same disk is not a good idea :

• From https://superuser.com/a/688758 :

Windows officially supports just one ESP per disk [...]. I don't know about Windows 8, but the Windows 7 installer will flake out if it sees more than one ESP on a disk; the installation will proceed part of the way and then fail.

• From https://news.ycombinator.com/item?id=16261695 :

There can only be one ESP and that's in the spec. You can have multiple partitions each assigned as /boot for a different OS, but there can only be one ESP which is used by the firmware to store its settings, etc.

The EFI spec is officially silent about the presence of multiple EFI system partitions on non-removable hard drives, but explicitly forbids multiple ESPs on removable disks, per §11.2.1.3:

For removable media devices there must be only one EFI system partition, and that partition must contain an EFI defined directory in the root directory

But in practice, Bad Things (TM) happen if you have more than one ESP on the boot disk.

I don't know if the first point still applies (Windows 10), but I've also read (I can't remember where) that sometimes Windows updates could mess up if 2 ESP are present on the same disk.

As a result of these "fears", and since my system is not already fully setup, I've decided to reinstall Arch Linux (keeping the dual boot), and using the same ESP (/dev/nvme0n1p1) created by the Windows install this time.

But before starting the reinstall process, I'm wondering : is it safe to remove the /dev/nvme0n1p8 partition (second ESP used for Arch)? In the BIOS, I've noticed that, in Boot sequence, there are currently two options :

• Windows Boot Manager
• arch

I can see the same result when running efibootmgr -v :

Boot0000* Windows Boot Manager HD(1,GPT, ...)/File(\EFI\Microsoft\Boot\bootmgfw.efi)
Boot0003* arch HD(8,GPT,...)/File(\EFI\arch\grubx64.efi)

So, if I understand correctly (tell me if I'm wrong), it looks like removing the 8th partition will only remove the "arch" option, and keep only the "Windows Boot Manager" on the 1st partition intact. Am I right?

I've removed the esp flag on this partition with parted (set 8 esp off). I'm able to boot into Windows (via Grub, or by defining "Windows Boot Manager" as the first option in the BIOS Boot Sequence screen). Now, I can remove the 8th partition from Windows disk management utility in Windows (not grayed anymore since I've set the esp flag off), but is it really safe? Will I still be able to boot into Windows after?

I'm also confused about Grub, what will happen after the removal of the 2nd ESP?