Grub2 Boot Windows directly

[masfur]

Good morning.
I have installed Ubuntu 16.04 on my pc. There is a tri-boot with Win8.1 and Win10.
In the grub menu, I have two options: Ubuntu and Windows Boot Manager.
When I click on WIndows Boot Manager, after I could choose Win8.1 or Win10.
There is a way to set grub menu for boot Windows directly from single partition?
Thanks.

[grahammechanical]

In the grub menu, I have two options: Ubuntu and Windows Boot Manager.

Are you sure that is the Grub boot menu and not the UEFI utility? Load Ubuntu and run this command and watch the printout,


sudo update-grub

The printout will list all the operating systems detected and that will be listed in the Grub boot menu. It should include 2 boot loaders for Windows. One each for Windows 8 & Windows 10.

Did you install Ubuntu in EFI mode or BIOS/Legacy/CSM mode?

Regards.

[oldfred]

Many UEFI systems will not work with two ESP - efi system partitions:

Dual boot two Windows UEFI from grub, two efi partitions.
http://askubuntu.com/questions/653101/boot-repair-windows-not-listed

[masfur]

Are you sure that is the Grub boot menu and not the UEFI utility?
Yes I'm sure. Ubuntu is the last OS that I installed, and I know the grub menu.
Now I try with a new file in grub.d directory with "chainloader+1" option.
Thanks to all for your replies.