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I want to install Ubuntu beside Windows 8 following this post on Ask Ubuntu guide, but I don't know if my Windows installation is booting in UEFI mode or in legacy mode (and it's said to be important in the post under the "DUAL BOOT ISSUES" paragraph). How do I get to know it?

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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.
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  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.
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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.

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