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

[Pascal Hambourg]

Le 14/12/2018 à 07:51, David Collier a écrit :
> On Thu, Dec 13, 2018 at 10:35 PM Pascal Hambourg <address@hidden>
> wrote:
>
> > Le 14/12/2018 à 06:13, David Collier a écrit :
> > > when I try booting from the usb stick it indeed shows two boot options,
> > > 'Patriot Memory PMAP' and 'UEFI: Patriot  Memory PMAP' but when I try
> > > picking the UEFI option it fails with message
> > >
> > > error: file '/boot' not found
> >
> > Is this a GRUB error ? Does it fallback to a grub rescue prompt ? If
> > yes, what do the 'set' and 'ls' commands display ?
>
> ah, it turns out it is. set shows a screenful of variables, in particular
>
> cmdpath=(hd4,msdos2)/EFI/BOOT
> config_directory=(hd4)/boot/grub/x86_64-efi
> config_file=(hd4)/boot/grub/x86_64-efi/grub.cfg
> ...
> grub_cpu=x86_64
> grub_platform=efi

At least it's booted in EFI mode (64 bits).
Partition #2 on the USB stick is the EFI partition.

> prefix=(hd4)/boot/grub
> ...
> root=hd4

Is it a normal "grub>" prompt will full features or a "grub rescue>" 
prompt with limited capabilities ?

If this is the normal "grub>" prompt, you should be able to manually 
load the config file from your installed system and boot the system in 
EFI mode.

insmod part_gpt
insmod ext2
set root=hdX,gpt3
configfile /boot/grub/grub.cfg

You'll have to find out which (hdX) is the /dev/sda drive which contains 
the system root partition.

> ls shows a bunch of drives, some with partitions, some without.

'ls' shows the partitions on a disk only when the module handling the 
partition table type (part_msdos, part_gpt...) is loaded. By default 
only required modules are loaded.