Re: 'error: invalid signature' when booting Windows 10

[Pascal Hambourg]

Le 11/12/2018 à 08:03, David Collier a écrit :
> grub_cpu         i386
> grub_platform  pc

This means, as I suspected, that the active GRUB flavour is GRUB BIOS 
booted in BIOS/legacy mode, not GRUB EFI. GRUB BIOS is unable to 
chainload an EFI executable such as the EFI Windows boot manager 
bootmgfw.efi. If you want to chainload it, you must boot in EFI mode 
with a GRUB EFI instance, as you did previously when the chainloading 
worked.

> prefix               (hd0,gpt3)/boot/grub

IIUC, (hd0) is the SSD containing the GNU/Linux system root filesystem ; 
the EFI partition (hd1,gpt3) containing Windows boot manager is on 
another drive (hd1).

You mentionned that you could reinstall Windows. Reinstalling Windows in 
BIOS/legacy mode would allow it to be chainloaded by GRUB BIOS ; but it 
would also require to repartition Windows' boot/system drive with a 
DOS/MBR partition table instead of a GPT partition table. Windows is not 
as flexible as GRUB and GNU/Linux with partition table vs. boot mode 
combinations.

Could you provide the previous and current drive/partition layout of 
this machine ?

> I wish I could read cmdptah - but it gets scrolled away from the screen and
> I did not find a way to read it,

With the following declaration, GRUB will pause after each page, a bit 
like 'more' does :

set pager=1