How do I repair Windows 10 UEFI/GPT disk which is left unbootable after deleting partitions?

Question

I recently upgraded from Win8 to Win10. The Win8 machine was in a dual boot with Ubuntu on an 80GB SSD. After the update and a few other issues I created while messing around with GRUB, I'm now left with only one partition on the drive: the Win10 OS partition. That's it! And... it doesn't boot... and I think that's because it's all alone without an EFI boot partition and MSR...??? At least that's what this and this have to say.

I've attempted a few times following several different guides to reinstate the other partitions I've read (http://technet.microsoft.com/en-us/library/hh824839.aspx) are necessary to boot Windows. But it still refuses to boot. I'm confident this can be done but I'm struggling with the how.

I have full access to Xubuntu via LiveDisk. I can access the Win10 partition from the LiveDisk. And while I apparently don't have enough rep to post it, I can provide a pretty screen grab from gparted showing the current state of my disk.

Solution

You create a EFI System Partition (at least 100MB) with any tool (also from Linux) and a MSR partition (exactly 128MB). These two partitions preferably at beginning of disk (if there is free space).

Then boot from Windows 10 installation USB/DVD (you can download Windows 10 ISO from Microsoft if you don't have it and use some Linux tool to make Windows 10 installation DVD/USB).

Then Repair, Automatic Repair (eventually 2-3 runs with rebooting after each run).

Comments

[deathangel908]

What if automatic repair "can't fix" ?

[Yorkziea]

UEFI Boot can be fixed with a single command - "bcdboot.exe n:\windows" where n: drive is drive of not booting Windows. Offline sfc can fix damaged system files.

[HarlemSquirrel]

The one line command did it for me after creating the EFI partition

[Kevin]

Some more info