Is my Windows installation booting in UEFI mode or legacy mode?

Solution 1:

If you would prefer to check from Ubuntu:

1. In Ubuntu open the terminal and type "sudo parted -l".
2. Scroll to the part with information on the disk your Windows installation is using. Under "Partition Table:" it should say gpt or msdos. GPT is required for Windows to run in UEFI mode. msdos means you're using BIOS/Legacy Mode.

Solution 2:

1. In Windows 8 go to the start screen
2. Right click on "command prompt", and choose "run as administrator". [If you can't find it look under all programs.]
3. In command prompt type "diskpart.exe".
4. In diskpart type "list disk". It will show a * under the GPT column for disks using GPT. Windows requires GPT in order to run in UEFI mode.

Alternatively, another Windows 8 method is as follows:

1. In Windows 8 go to the start screen
2. Click on "command prompt" [If you can't find it look under all programs.]
3. In command prompt type "msinfo32". Under "BIOS MODE" it should say UEFI if you are running in UEFI mode.

Solution 3:

The post you mention (Installing Ubuntu Alongside a Pre-Installed Windows with UEFI) already reports the command to launch:

[ -d /sys/firmware/efi ] && echo "Installed in EFI mode" || echo "Installed in Legacy mode"

It's an elegant line that checks for you whether the directory /sys/firmware/efi exists. If so, then your system is in EFI mode, else it is in legacy mode. Look at ls /sys/firmware, more simply.

The answer already given with sudo parted -l is also valid, but it infers the answer from the way the partition table has been constructed.

Usage notes

I am aware that these commands are useless if you haven't installed Linux yet, but some viewers may come across this question in retrospect, for example near the point of re-installation and so forth.

However, from the live USB/CD you can launch sudo parted -l in a terminal and see the requested information. For this use do not trust the information from /sys/firmware/ though, because it refers to the system in the live medium, rather than that in your computer.