After re-installing Kubuntu on my (EFI, GPT) laptop (which also has Windows 10), I've ended up with a broken grub. It used to work fine.

The problem is that now it boots into grub, with no configuration, just the grub> prompt.

I can continue by typing:

grub> configfile (hd0,gpt6)/boot/grub/grub.cfg

which then brings up the usual menu.

But I'd like to know how to configure grub so that it finds it automatically!

Needless to say, I have already tried running grub-install /dev/sda after booting.

(Which succeeds without error)

Any suggestions?

PS. I don't want to totally blank the drive, as it shares with a Windows 10 install that I'd like to keep.

Thanks

Toby