<< Solved >> GUID scheme disks: can I get rid of unwanted EFI partition?

[Tazling]

Little hints here and there online suggest that some of the hair-tearing confusion I'm experiencing with UEFI boot disks and Win10 dual-booting may be because ASUS BIOS doesn't like too many EFI partitions and Win10 installer really doesn't like multiple EFI partitions.

Unfortunately, I always formatted my disks GUID because I figured every disk is a potential EFI backup (rescue) device. So I have an EFI partition on my boot disk, and one on the target disk that I'm trying to make also bootable as a backup, and one on each of my data disks... But maybe this is not so smart. It's actually a royal PITA trying to keep them all in synch.

Anyway, can I get rid of unused EFI partitions by... renaming them to something other than EFI, if diskutil will allow me to do that? by changing their format to something other than FAT? can I delete the EFI partition and just waste that 200MB of disk space?

One reason I'd like to reduce the EFI body count is that the pop-up menus on my ASUS mobo BIOS are not exactly intelligent if there are more than about four items in the boot device list, then when my cursor is on the top (first priority) boot slot, the top of the list becomes invisible behind the master toolbar (so you can't select the top one or more devices). There's a workaround: I can Disable all 6 slots, then set the lowest priority one only (the whole menu is visible if my mouse is that far down the page) -- which will immediately become the first priority. But I'm not sure how well this really works, because often when I do this, on the next boot all the slots are Disabled again. If anyone knows how to work around this peculiar inflexibility of the ASUS BIOS GUI, I'm all ears.

If you want to dual or triple or whatever-boot a Hackintosh, do you need N disks with N EFI partitions, one for each OS you install? If I ever do succeed in getting Win10 to install on this system (which is looking less and less likely as I exhaust my own and other people's ideas), will my Win10 boot disk have its own distinct EFI partition?

 

[Going Bald]

You can use diskpart to delete a partition and leave free space behind:
diskpart
list disk
select disk x //disk x being disk that contains the partition you want to delete
list part //displays a list of the partitions on the selected disk
select part 1 //assuming partition 1 is the partition you want to delete
delete part override // override flag is needed because EFi partition is a protected partition.
exit
exit

 

[Tazling]

@GB thanks! at present you are my guide through the labyrinth. I've googled a couple of fragmentary hints here and there about Things that can Go Wrong with Win10 Install (seems like quite an inventory!) so am steadily adding to my list of variations to try. One fallback position might be to install a regular SATA SSD (laptop style) and try installing on that rather than the M.2 or PCIe SSDs. If I disabled all SATA units except the SSD, perhaps Win10 would correctly target it?

 

[Tazling]

Answer: Yes you can get rid of the EFI partition on GPT disks and reclaim the space BUT, apparently under MacOS if you do this, Disk Utility won't like it and you may have issues erasing or reformatting later.

"I noticed a funny thing about having a EFI partition. If you delete this partition after the Disk Utility has created it, then the Disk Utility will not format the other partitions, on the same disk, with any type of file system. This means the Erase and Add partition operations will fail."

Why does Disk Utility create EFI partitions on external disks?

A technical told me about the EFI partition that... ...it's only there in case your computer will do an EFI update so the update files can be loaded onto the EFI partition. This is consistant wit...

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