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I'm trying to fix a problem on someone's laptop. The problem is that after installing Ubuntu 16.04.3 LTS, the GRUB doesn't boot into previously-installed Windows 10. The Windows 10 is among the GRUB menu items, but when selecting the Windows 10 menu item, the system doesn't boot into Windows and restarts instead.

I was also receiving signature errors while playing around with GRUB command line options.

I tried boot-repair but it couldn't resolve the problem. The boot-repair report is available at the following link:

http://paste.ubuntu.com/25763771/

The Boot-Repair Boot Info Script shows this at the end of the Boot Info Script:

update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.10.0-28-generic
Found initrd image: /boot/initrd.img-4.10.0-28-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
Found Windows 10 (loader) on /dev/sda1
Found Windows 10 (loader) on /dev/sda2
NTFS signature is missing.
Failed to mount '/dev/sda7': Invalid argument
The device '/dev/sda7' doesn't seem to have a valid NTFS.
Maybe the wrong device is used? Or the whole disk instead of a
partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around?
mount /dev/sda7 : Error code 12
mount -r /dev/sda7 /mnt/boot-sav/sda7
NTFS signature is missing.
Failed to mount '/dev/sda7': Invalid argument
The device '/dev/sda7' doesn't seem to have a valid NTFS.
Maybe the wrong device is used? Or the whole disk instead of a
partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around?
mount -r /dev/sda7 : Error code 12

I ran:

$ sudo mkfs.ntfs -Q /dev/sda7

And the signature messages at the end of boot-repair report got resolved:

http://paste.ubuntu.com/25764357/


On GRUB command line, accessible by pressing e when GRUB menu is display, when I enter the following commands:

    insmod part_gpt
    insmod ntfs
    set root='hd0,gpt2'
    chainloader /bootmgr

I receive the following error message:

>  Booting a command list
> Error: invalid signature
>  Press any key to continue ...

And when I press any key, the machine reboots


I think the problem is mentioned in this post. The CSM option is enabled on my firmware setup. Therefore, I think Ubuntu is installed with GRUB in BIOS mode instead of UEFI mode. And my disk uses GPT, therefore Windows 10 can only be loaded by a UEFI boot loader not a BIOS boot loader.

What I'm going to do now, is to disable CSM on my firmware setup and then boot with Ubuntu live DVD and then try to install Ubuntu in UEFI mode.

The problem is further explained here

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    @karel It solved the signature messages at the end of boot-repair report, yet, I cannot boot into Windows 10, and it still restarts the computer – user3405291 Oct 18 '17 at 8:06
  • Please take a look at this question: askubuntu.com/questions/217904/… I don't believe that it's an exact duplicate of your question because you also solved the signature error, but it may help from here on. – karel Oct 18 '17 at 8:10
  • @karel Great, I'm going to work on it – user3405291 Oct 18 '17 at 8:22
  • Reinstalling Ubuntu in UEFI-mode will help you a lot! – mook765 Oct 18 '17 at 9:12
  • @mook765 Right, I'm installing Ubuntu in UEFI-mode – user3405291 Oct 18 '17 at 9:38

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