I'm trying to make a USB Windows 8.1 bootable from a Windows 8.1 ISO file. My problem is that I don't have any OS on my PC, I just have a live-usb Ubuntu. And it is the problem, every tutorial, everything I tried requires to install a program (such as grub, unetbootin, mkusb, WinUSB, WieUSB etc...) : 1) Here, it is not the same problem, because he's not in a Live-USB Ubuntu How can I create a Windows bootable USB stick using Ubuntu?
2) I tried the dd method, but it doesn't work. This guy tried it and has the same problem How can I create a Windows 10 boot usb from ubuntu?
3) That tutorial is well detailed, but there is a problem, I don't know whether I have to use GTP or DOS partition table, it is unclear and everyone seems not to be sure about what is right https://onetransistor.blogspot.ch/2014/09/make-bootable-windows-usb-from-ubuntu.html
4) I want a EFI boot because I'm sure that the BIOS could not work with my computer. My ISO take in account the EFI because there is a directory called EFI.
5) I don't have any Windows machine to use Rufus or WIN32.
6) I CAN'T install program, because I'm in a live USB mode, anyway, I've tried to install (for using the programs that must be installed) Ubuntu on my SSD but at the end, it tells me that there is a problem with GRUB (my Ubuntu boot is in EFI mode), and I think that I can't install grub because I'm in a liveUSB...
I think that my only hope is mkusb-nox, which is a command-line tool, but I need to install it too if I have understood?? How can I use it without installing. Is there any solutions to my problem?
I'm sure that I have read everything possible but the problem is really that I can't install in /root a program, because I'm in a LiveUSB mode. I'm really lost and out of solutions.
PS : I've tried the solution consisting in formatting the USB in NTFS, put the "boot" flag and copy (using cp -r /mountpoint/* USBKEY) but it doesn't work, I really don't understand why. Do I need to install Grub on the USBkey? If yes,how can I do it knowing that grub can't be installed because of the live mode.
Sorry for the long message but I try to give everything to you. As you have understood, it is my non-persistent live USB that is really the problem
thanks a lot for your help!
J. PS : My goal is to install Windows on that computer, not making a dual boot. PS2 : I use Ubuntu 16.04 live USB