Linux Mint installer asking me if i want to "Force UEFI Installation"

[cxf]

I am in the process of installing Linux Mint and after I created the partition table a pop-up appeared with text saying:

This machine's firmware has started the installer in UEFI mode but it looks like there may be existing operating systems already installed using "BIOS compatibility mode". If you continue to install Debian in UEFI mode, it might be difficult to reboot the machine into any BIOS-mode operating systems later.

If you wish to install in UEFI mode and don't care about keeping the ability to boot one of the existing systems, you have the option to force that here. If you wish to keep the option to boot an existing operating system, you should choose NOT to force UEFI installation here.

-The partition table that I just made had an EFI partition.
-When I set the ISO up with Rufus I used GPT/UEFI only.

-My BIOS is in UEFI only mode, and I remember checking and seeing an EFI partition in Windows 10. Is that an unreliable way to check that?
-I'm dual booting these by installing LM on the other hard drive while the Win10 hard drive is disconnected.

Do I need to start everything over by making the USB stick with the comparability mode enabled or can I just remake the partition table without the EFI partition.

Edit: The UEFI/BIOS settings don't even allow you to turn off UEFI only. It's black and unchangeable. (I remembered that when I saw the screenshots I took earlier. I'm still in the installation screen.)
Edit 2: The "Go back" button does nothing.
Edit 3: "ls /sys/firmware" lists efi, so the installer is in UEFI mode. Not a surprise really since the popup said that but thought I'd say that anyway.

[gm10]

Ok, 90% of your post says you want to install in EFI mode but then at the end you ask how to install in legacy mode?

Going with the 90% here (= you wanting an EFI install) and your description that there is no other operating system on a connected drive (i.e. your Windows drive is disconnected and the drive for Linux is blank and you only just partitioned it) then you can simply ignore the warning and proceed with the installation.

[cxf]

Ok, 90% of your post says you want to install in EFI mode but then at the end you ask how to install in legacy mode?

Going with the 90% here (= you wanting an EFI install) and your description that there is no other operating system on a connected drive (i.e. your Windows drive is disconnected and the drive for Linux is blank and you only just partitioned it) then you can simply ignore the warning and proceed with the installation.

Okay thanks.
The reason I asked if I need to do it in legacy mode is that I wasn't fully sure that Windows is in EFI mode. (I am not experienced with this)

So once I have ignored the warning and installed it, will it work normally when I reconnect the Windows drive (and update grub)? I'm trying to achieve a dual boot with separate drives.

[gm10]

If your UEFI wasn't in legacy mode then neither was your Windows, so everything should be fine.

[cxf]

If your UEFI wasn't in legacy mode then neither was your Windows, so everything should be fine.

Alright. Thanks a lot.
I'll continue with UEFI forced and hope for the best

[cxf]

The "continue" and "go back" buttons on the popup do nothing. I can't close the popup either.
Since the popup is active I can't press continue or back on the main installation window either.

[gm10]

Can't help with that, maybe something you did in the meantime is tripping it up. Reboot, try again? /shrug

[cxf]

I found that some other people had the same problem a while ago. https://askubuntu.com/questions/693732/ ... ion-window and https://bugs.launchpad.net/ubuntu/+sour ... ug/1547286
I'll try rebooting and disabling WiFi.

Edit: Keeping WiFi turned off worked! Now I'll cross my fingers and hope that dual booting works too.

[gm10]

I found that some other people had the same problem a while ago. https://askubuntu.com/questions/693732/ ... ion-window and https://bugs.launchpad.net/ubuntu/+sour ... ug/1547286
I'll try rebooting and disabling WiFi.

Edit: Keeping WiFi turned off worked! Now I'll cross my fingers and hope that dual booting works too.

Interesting. I'll make a mention to Clem. Without a reproducible test case (and I'm not sure I understand what's actually triggering this for you - it cannot be a common thing or I'd have seen this come up before) this may be hard to fix but it could be mentioned in the release notes.

[cxf]

Okay. I managed to get it working. I had a few issues though.
The installation went really quickly, it told me that I needed to reboot and I did that.
Well. When it was booting up I pressed F12 to ensure that it boots into Linux Mint and not into the USB. The only thing listed was the USB stick. Without it my PC told me that I didn't have an OS installed.
I googled the issue and found a post that instructed me to run the Ubuntu boot repair from the Live USB.
It worked!
I was now able to boot into Linux Mint normally.
I can share the Ubuntu repair log if necessary.

I haven't tested whether Windows 10 works alongside with it yet. I'll likely test it out tomorrow.

Thanks for helping me out!

[gm10]

Hmm, sounds like either the installer is quite incompatible with whatever your setup was, or you didn't set it up correctly (something wrong about your EFI partition or you didn't select it in the installer). I don't think the log is necessary for that part, thanks, it's pretty clear it didn't install GRUB correctly or at all.

[gm10]

To keep you in the loop: The issue has been identified and has been fixed for future releases. Release notes for 18.x and 19-19.1 have been updated to include the workaround. Thanks for your help with this.