upgrade Windows 10

Question

in this moment I have windows 8.1 and Ubuntu 14.04 and boot works in this moment. How can I upgrade my Windows from 8.1 to 10 with out destroy my boot between linux and windows?

Answer 1

You can't.

If you want to upgrade to Windows 10, you'll have to reinstall your bootloader, since Windows will wipe it from existence.

To install the bootloader:

1. Boot the machine using a Live CD.

2. Open a terminal.

3. Find out the name of the internal disk by using fdisk to look up the device's size.
   For example:

   sudo fdisk -l
   

4. Install GRUB boot loader onto the proper disk (the example below assumes it is /dev/sda):

   grub-install --recheck --no-floppy --root-directory=/ /dev/sda
   

Source