Grub menu did not appear at all.
I got only this message:
error: symbol grub_disk_native_sectors not found

And grub prompt:
grub>

I failed to set root partition to any of the 3 partitions.
set root=(hd3,ext2)

Funny thing is that grub identified ext4 partition as ext2
it is where my /boot folder is located.

I think "apt upgrade" kernel spoils grub configuration.