Re: problems dual booting Ubuntu 16.04 and Windows 10

[Pascal Hambourg]

Le 10/05/2018 à 21:27, David Collier a écrit :
> Not sure if this message will me attached to the original thread or not,

Not unless you added a References: header field attaching it to the thread.

> > Did you install Ubuntu and Windows in the same boot mode (EFI or BIOS) ?
>
> Yes, both installed using UEFI, on a computer which already had Ubnuntu I
> added a hard drive and installed Windows 10 on it.

The end of your reply indicates that Ubuntu does not boot in EFI mode.

> > > 'disks' utility to change format of the Windows boot partition from FAT to
> > > NTFS, converting it to NTFS makes the BIOS stop recognizing it, but still
> > > does not help grub to recognize it.
> >
> > Do you mean the EFI partition ? The BIOS does not care about Windows boot
> partition.
>
> I guess this is a terminology discrepancy,

No it's not. The UEFI firmware does not care about Windows boot 
partition. All it cares about is the EFI partition.

> > fdisk -l
>
> $ sudo fdisk -l /dev/sdc

This is not what I asked for. Please provide the complete output.

> > blkid
>
> $ for d in /dev/sdc*; do blkid $d; done

This is not what I asked for. Please provide the complete output.

> /dev/sdc1     2048   1023999   1021952   499M Windows recovery environment
> /dev/sdc2  1024000   1226751    202752    99M Microsoft basic data
> /dev/sdc3  1226752   1259519     32768    16M Microsoft reserved
> /dev/sdc4  1259520 976773119 975513600 465.2G Microsoft basic data

This does not look like blkid's output.

> $ sudo os-prober
> /dev/sde1:unknown Linux distribution:Linux:linux

Ok, os-prober is installed.

> $ efibootmgr -v
> efibootmgr: EFI variables are not supported on this system.

This means that the system did not boot in EFI mode. It explains why 
os-prober cannot detect Windows EFI boot loader.
Check what's in /boot and /boot/grub : I guess there is no /boot/efi 
directory nor /boot/grub/x86_64-efi, but there is a /boot/grub/i386-pc 
directory.