Dual Booting Windows 10 and Ubuntu 20.04: Grub bootloader

[Dave3000]

I was installing Ubuntu 20.04 on my 500GB SSD. Windows 10 was installed on my 250GB NVMe SSD. I chose the EFI partition to install the grub bootloader on my 500GB SSD that was created during the Ubuntu installation when I set up the partitions for Ubuntu. However, after I finished installing Ubuntu on 500GB SSD, it actually did not install the grub bootloader to the EFI partition on the 500GB SSD that I specified during the installation. Instead it installed the grub bootloader to the 100MB EFI partition on my 250GB NVME SSD, which is the SSD that Windows 10 is installed on. The BIOS on my motherboard does not have an option to disable the NVMe ports. Is it necessary to disconnect my 250GB NVMe drive, the physical drive that Windows 10 is installed on, before I install Ubuntu on the 500GB SSD if I want to have the grub bootloader to install on the physical drive that Ubuntu is installed on? I really don't want to open up my PC and disconnect my NVMe drive as it's too much work removing the heatsink, especially with the sticky thermal pad that is literally glued to the NVMe drive, and then reinstalling the NVme drive, and carefully installing the heatsink with precision as it has to line up with the screw holes on my motherboard for the NVMe heatsink, especially with the sticky thermal pad sticking when the heatsink is not lined up with the motherboard's scew holes for the NVME heatsink. I once did that and I had a very difficult time removing the heatsink for the NVMe and an even more difficult time installing the heatsink for the NVMe because of the sticky thermal pad and small screw holes on the heatsink, as I can barely see through the screw holes of the heatsink, which makes it difficult for me to line up the heatsink.

 

[crashtech]

It's certainly possible to install grub on the drive of your choice, but you have to watch the directions during setup very carefully. Typically I disconnect drives that contain other OSes during other OS setups, then use the PCs built in boot menu to select between them, but in your situation where it is found to be difficult, there's a need to exhibit better discipline in knowing which drive is which upon installation. Install grub on the same drive that you wish to install Mint on. It should "see" the Windows installation and include an option to boot to it.

 

[Dave3000]

As I mentioned I did choose the drive that Ubuntu was to be installed on which is the 500GB SSD during the Ubuntu setup after creating the partitions for Ubuntu. Where it says "the device which the bootloader will be install on" I chose the EFI partition that I created during the partition setup for Ubuntu. Partition 1 was the EFI partition sized to 200MB. Partition 2 was the \ partition sized to 30GB. Partition 3 was the swap partition sized to 8GB, and finally Partition 4 was the Home partition, taking up the rest of the SSD space. I chose Partition 1 (EFI partition) on the SSD that Ubuntu was installed on as the device to install the grub bootloader. It seems that the installation ignored my choice of device for the bootloader, as there was nothing that partition and it did not mount either after loading Ubuntu. I checked this with the Disks application in Ubuntu. Also when I ran diskpart in Windows 10 afterwards, it showed an ubuntu directory on the 100MB partition of the SSD that Windows 10 was installed on, and nothing in the EFI partition of the SSD that Ubuntu was installed on.

 

[crashtech]

All the drive info in setup should have something like sda1, sda2, etc. These designations are absent in your posts.

 

[Dave3000]

I chose sda1 as the device to install the bootloader which was the first partition I created as the EFI partition on the Samsung 860 EVO 500GB SSD.

 

[Fallen Kell]

The issue you are running into is due to UEFI. I believe the spec does not allow for multiple UEFI boot partitions, and as such, it is using the one already configured on your system based on your UEFI boot BIOS settings.

You can disable UEFI boot on some motherboards/BIOSes (usually called legacy boot/mode), or you can possibly enable a hybrid mode (sometimes listed as "both"). You also need to ensure that the instalation method you are using booted in legacy mode (assuming you particular Linux distribution still supports it) and then you can install Grub on your second disk under a "/boot" partition and as a MBR section of the disk you want to use.

That being said, as long as you format the second disk with a UEFI boot partition, even if it is not using it, you should be safe in the event that your windows 10 disk fails as you can boot from a DVD/USB, and use recovery mode to reinstall Grub to the other disk and you should be all good to go.

 

[postmortemIA]

You can have multiple EFI partitions, just not more than one on one disk. Ubuntu's install likes to hijack the Window EFI partition and add its own entry. No big deal, you can resort them in BIOS/UEFI settings. You can also remove them using efibootmgr utility.

 

[rasczak]

If you don't mind me asking, why aren't you virtualizing one of the OS installs? Install either OS natively, then virtualize the other using a number of free virtualization tools, hyper-v, virtualbox, ovirt, etc.