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

[Pascal Hambourg]

Le 13/12/2018 à 07:49, David Collier a écrit :
> On Wed, Dec 12, 2018 at 10:22 PM Pascal Hambourg <address@hidden>
> wrote:
>
> > Isn't there a labelled boot entry for GRUB/Linux in the EFI boot menu ?
>
> no, there is not, GRUB/linux is booted when "P1: Samsung SSD 850 PRO 1TB"
> is picked.
>
> > Is there a line in /etc/fstab to mount the EFI partition on /boot/efi ?
>
> no, there is no line in /etc/fstab and there is no /boot/efi in the mount
> command output
>
> > Is there a GRUB instance in (/boot/efi/)EFI/* on the EFI partition ?
>
> i.e. /boot/efi is empty

/boot/efi is a mount point for an EFI partition. If the EFI partition is 
not mounted on it, it appears empty. Add a line in /etc/fstab to mount 
the EFI partition /dev/sdb3 by UUID (from blkid) as vfat on /boot/efi 
and mount it.

> Is there a directory /boot/grub/x86_64-efi ?
>
> no, but there is  /boot/grub/i386-pc full of GRUB modules

These are GRUB PC modules. So GRUB EFI was not installed on this system.

You must install GRUB EFI for the architecture matching your UEFI 
firmware (32 or 64 bits, most likely 64 bits - NOT the CPU 
architecture), but grub-install will be able to register an EFI boot 
entry for itself only if the system was booted in EFI mode. What is the 
installed distribution ? The installer of some distributions provide a 
rescue mode which allows to chroot the installed system. Also you can 
boot a live system in EFI mode and run grub-install from there using the 
proper --boot-directory and --efi-directory options. Or you can boot the 
installed system in EFI mode with something like GRUB Rescue.