I'm trying to install Ubuntu 16.04 from a USB onto my brand new SSD, but I get the following message (see below). I've seen a bunch of posts about this, but none involving installing onto a new hard drive that doesn't currently have any operating systems installed. At an earlier stage in the process the computer told me that no OS's were detected.

I get no response whether I click "Continue", "Go Back", or even try to close the window. Help?

The message:

"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."

  • do you have Windows installed in Legacy mode?
    – ravery
    Nov 19, 2017 at 13:40
  • it's a brand new drive. nothing is installed on it.
    – Y T
    Nov 19, 2017 at 13:42
  • ok two things to check. 1) is the ATA controler set to AHCI and 2) is the drive partitioned with GPT?
    – ravery
    Nov 19, 2017 at 13:44
  • sorry, how do I check these things?
    – Y T
    Nov 19, 2017 at 13:46
  • could this have something to do with it?: when I run ubuntu live directly from the USB LiveDisk, and then run sudo fdisk -l, the USB LiveDisk itself is listed as Type: EFI (FAT-12/16/32). it's also listed as "Disklabel type: dos"
    – Y T
    Nov 19, 2017 at 13:55

1 Answer 1


Well, since the SSD is new, I decided to go with the default option of "Erase disk and install Ubuntu" instead of specifying my own partition table as I usually do. And this led to a successful install.

My guess as to the problem is that I was specifying the root partition as "ext4 filesystem" instead of ESP. Can someone comment as to whether this diagnosis is correct?

EDIT: It is correct. I confirmed by re-installing with my own partition table as follows: EFI System Partition (ESP) at the beginning of the drive with around 570MB of space, and then partitions for root, home, and swap. Thanks for the help!

  • you are not correct, the issue is that the disk is partitioned MBR instead of GPT. So without the ESP, the installer thought that the drive had a Legacy System installed on it. As I stated in the above comments, EFI prefers a GPT partitioning. It can run on an MBR disk, so leave it if already installed. But if you reinstall, consider switching to GPT partitioning.
    – ravery
    Nov 20, 2017 at 6:19
  • @ravery how can I partition GPT? Can I do that using Ubuntu bootable usb or do I need gparted bootable usb for that? Jul 13, 2020 at 15:42

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