Gfilui

I would like to have two OSs without dual boot.
Two drives, two OSs (Ubuntu + Windows 10), full separation of concerns.

The choice what to boot will be handled by Boot menu from the motherboard.

How to install them without any interference between them?

Helper questions:

• Do I need to manipulate the boot flags or booting priority in UEFI/BIOS?


• Do I need to remove a drive to be safe in this process? To remove second m.2 drive I need to take out the motherboard.


• Should I do it in some order? Like 1. Windows 2. Ubuntu

I know a few ways of installing Ubuntu but I want to know which is easiest and safest. For now I did it the hard way by removing the drives.

Aravid and Bajiru gave excellent answers but both seem to have missed your second bullet.

You do not need to remove the drives in order to seperate the OS's; However you must be careful where you install the boot loaders.

If you are using Legacy boot, then the the boot loader needs to be installed to the MBR of the respective drive, ie Windows in the windows drive's MBR and Grub in the Ubuntu drive's MBR.

If you are using EFI, then each drive needs to have an EFI partition. with the appropriate EFI boot file in it. Note: when installing ubuntu in EFI mode, Chose something else, then select the partitions that Ubuntu should use for the install.

PS: since Windows doesn't allow the versatility in installation that Ubuntu does, I would install Windows first to the first HDD, then Ubuntu on the second drive.

Backup your ubuntu files before you start this activity. This should work!

Try gnome-disks in ubuntu:

connect both drives and type:

sudo gnome-disks

This is ubuntu file system. You suppose to have only 1 partition.

Select the windows drive > then the partition > Additional options > Edit mount Options.

Unselect automount option and mount at startup. And save and exit.

This will force ubuntu not to mount during bootup.

For windows:

You have to unassign the letter and unmount the hard-disk.

1) It will show you hard disk error. Just ignore it.

2) Press [Windows Logo] + R to open run prompt and type "diskmgmt.msc" in Open text box.

3) It will show 2 harddisk. Select your ubuntu hard-disk. If any letter is assigned remove the letter and select option not to assign letter as in this below article.

https://www.digitalcitizen.life/how-hide-or-dismount-partition-windows

https://superuser.com/questions/295913/how-to-mount-and-unmount-hard-drives-under-windows-the-unix-way

During this process, if windows mark dirty bit to your ubuntu hard-disk. Follow the below article:

How to correctly fix a "dirty" NTFS partition without using chkdsk

During bootup: keep the most used OS's hard disk on top. And to switch the os, press F10 and change the hard disk.

You don't have to follow a specific order. Just install Windows first on whichever drive you want in order to have something to boot after installation. Then, install Ubuntu on the other drive as usual.

After installation of both operating systems, you should modify the BIOS in order to make the boot menu (which drive to select) visible at every boot so that you do not have to press a specific button (such as F12) every time.

If you want to access your Windows (NTFS) drive from Ubuntu, you have to install ntfsprogs & ntfs-3g by typing the following command in the Terminal: sudo apt install ntfsprogs ntfs-3g. Vice versa (accessing Ubuntu drive from Windows) is not supported. Also, if you want to edit any partition, it's best to do it via Ubuntu using GParted. Install it via Ubuntu Software Center or by typing sudo apt install gparted in the Terminal.