grub ist:
1. bootmanager
2. boot init für Partition

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long version see:    debian_uefi_bootfaehig_machen-reinstall.txt

1. UEFI Modus? Check that the computer booted in computer in EFI mode:

 [ -d /sys/firmware/efi ] && echo "EFI boot on HDD" || echo "Legacy boot on HDD"
     should return "EFI boot on HDD".

2. check that your EFI system partition (most probably /dev/s
da1) is mounted on /boot/efi

 mount /dev/sda1 /boot/efi

3. possibly reinstall the grub-efi package

   apt-get install --reinstall grub-efi

4. Put the debian bootloader in /boot/efi and create an appropriate entry in the computer NVRAM

 grub-install /dev/sda

5. Re create a grub config file based on your disk partitioning schema

 update-grub


You should check afterwards that: 
1. the bootloader is existing in /boot/efi/EFI/debian/grubx64.efi and
   file /boot/efi/EFI/debian/grubx64.efi

2. the nvram entry was properly created.

 efibootmgr --verbose | grep debian

You can now reboot, and Grub should greet you.


You should check always:

1. EFI entries by running "efibootmgr"
   probably delete some entries by running "efibootmgr -b <####> -B"

2. nvram Boot Order Priorities

3. UEFI Hard Disk Drive BBS Prioritis