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From my understanding, the Grub2 bootloader can be installed on any EFI System Partition (ESP), specifically under \EFI\ubuntu.

I have 2 SSDs - with 3 ESP on each of them (for testing purpose):

  • /dev/sda has sda1, sda3, sda5 as ESP
  • /dev/sdb has sdb1, sdb3, sdb5 as ESP

I wasted my time last night only to test the following scenarios for this bootloader installation option:

  • Mount /dev/sda2 as root / and select the same device, eg: /dev/sda for bootloader installation
  • Mount /dev/sda2 as root / and select the ESP on the same device, eg: /dev/sda1, /dev/sda3, /dev/sda5 for bootloader installation
  • Mount /dev/sda2 as root / and select a different device, eg: /dev/sdb for bootloader installation
  • Mount /dev/sda2 as root / and select the ESP on a different device, eg: /dev/sdb1, /dev/sdb3, /dev/sdb5 for bootloader installation

img (image for illustration purpose, not my real test case)

No matter what I select, the bootloader (\EFI\ubuntu) is always installed on the first ESP of /dev/sda drive - the sda1. Edit: even when I mount sdb2 as root / and choose sdb for bootloader installation, the bootloader is still installed on /dev/sda1, meaning if I remove the 1st SSD, the system won't be able to boot!

What is the point of this option if it always choose the first ESP partition found on the system anyway?

  • I think you need to mount the desired ESP at /boot/efi and then run sudo grub-install, that should install the bootloader on the chosen ESP. In EFI-mode the boot-loader will always be installed to the ESP mounted at /boot/efi, thus you normally don't need to specify a device. If no ESP is mounted, the system will search and use the first found ESP. – mook765 Jul 12 at 13:14
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    While you may have multiple FAT32 partitions to use as ESP - efi system partition, only one per drive can be an ESP at a time. Grub correctly installs to ESP you specify, but Ubiquity installer does not use any info you give it during install, so grub never knows Posted work around to manually unmount & mount correct ESP during install: bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1396379 Before work around and if I wanted grub on flash drive, I copied /EFI/ubuntu & /EFI/Boot to flash drive's ESP. Same with sdb's ESP, but also had to use efibootmgr to add UEFI entry. – oldfred Jul 12 at 15:32
  • Thanks you 2 for your answer. Looks like it is a bug of the Ubiquity installer. I decided to switch to Lubuntu for a change. The Calamares installer and LXQt look much more friendly. – Livy Jul 13 at 17:25

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