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I have a fresh Windows 10 install on an SSD (sda). Now I want to add a second SSD (sdb) and install Ubuntu on it in such a way that there will be a separate EFI partition on sdb with the Ubuntu bootloader (GRUB) installed there and NOT on the EFI partition on sda. How do I accomplish this? I know there is an option to select "Device for bootloader installation" during the Ubuntu installation but it has been reported that this selection is ignored due to a bug: https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1396379

Also there is this peculiar guide on how to install Windows and Ubuntu on spearate disks: https://askubuntu.com/a/1126970/1158552

It somehow ends with the Ubuntu bootloader being installed in both EFI partitions on the two separate disks... How is this even possible?

Kind regards

Eugene T.
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  • There's only supposed to be one EFI partition for all operating systems for one device. That's how EFI is designed. It's commonly misunderstood that this will somehow affect your Windows bootloader - it doesn't. However if you want to do your own thing, physically disconnect the disk with the other operating system(s) when performing an installation. The installation can't affect your other disk if it doesn't exist during installation. You may have to deal with the fallout of having multiple EFI as this can regularly confuse your BIOS (since it's not supposed to be that way) – Nmath Dec 14 '20 at 21:06
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    @Nmath UEFI does not impose a restriction on the number or location of System Partitions that can exist on a system. System Partitions are discovered when required by UEFI firmware by examining the partition GUID and verifying that the contents of the partition conform to the FAT file system as defined in... (from UEFI-specification) – mook765 Dec 14 '20 at 21:32
  • @mook I didn't say it was not possible or restricted in any way. But I have advised of the potential real world consequences of having multiple ESP as it pertains to dual boot config. For example, with more than one ESP, the motherboard firmware can switch boot order based on the last booted OS or when there are system updates (especially Windows updates) – Nmath Dec 14 '20 at 21:43
  • Don't use/make a separate ESP. Windows has already made one, and Ubuntu will be quite happy to add its folder to it and share it when you install. – Paul Benson Dec 14 '20 at 22:25
  • Unplug your Windows drive sda when installing Ubuntu to sdb. Boot your Ubuntu installer in UEFI mode. Perhaps create your USB using Rufus with GPT selected under partition scheme, this will ensure UEFI install. I have never had a problem booting multiple drives with their own EFI partitions. – C.S.Cameron Dec 15 '20 at 02:48

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