I had to reinstall Windows 10 for one particular reason and Windows Boot Loader wasn’t working quite right, so I have tried to fix it under Linux. And accidently deleted the whole /boot folder …oops. As Linux /boot folder was placed also in ESP folder, originally created by and for the Windows first installation.
But before this oopsie deletion I have saved as a back-up at least something from /boot folder, or maybe even everything. There is a Microsoft folder, /grub folder with bootx64.efi and bootx64.efi.grb (though EMPTY!) and /Debian folder with shimx64.efi etc…
I have tried to fix the problem with “recommended options” of Boot-repair Live-CD, but it didn’t help. I can boot into GRUB but it doesn’t see anything and shows me just a command line (I mean GRUB line, not Debian OS).
I have also tried to install Refind with Gnome Live-CD, it can see grub file, but again, it boots me into blank GRUB without OS.
With Debian Live I have tried to follow advices at
https://askubuntu.com/questions/145241/how-do-i-run-update-grub-from-a-livecd https://wiki.debian.org/GrubEFIReinstall1) I have created a new ESP partition (on the other disc), so that to make it different from Windows boot drive. BTW, is it OK to have two partitions with ESP and boot flags..?
Forget to say my root folder and home folder of Debian are OK. At least as I can see from Live USB.
2) I have “chroot /mnt”-ed and edited /mnt/etc/fstab with a new /boot/efi drive (new UUID)
It was
# /boot/efi was on /dev/sda4 during installation
#UUID=44D6-6C36 /boot/efi vfat umask=0077 0 1
I made it
# /boot/efi was on /dev/sda4 during installation
UUID=55C0-916E /boot/efi vfat umask=0077 0 1
3) But when I tried to
grub-install /dev/sdb
it says Finished without errors
but update-grub
Shows
Syntax errors are detected in generated GRUB config file.
Ensure that there are no errors in /etc/default/grub
and /etc/grub.d/* files or please file a bug report with
/tmp/grub.cfg.new file attached.
When I try to load Refind or Debian boot sector in UEFI it again shows just blank GRUB