A few years ago I used to backup the MBR of a (now old) laptop with:
dd if=/dev/sda of=mbr_63.backup bs=512 count=63
Well, this was the first 63 sectors, a bit better than the MBR only, I think.
Will that still be valid for a more recent laptop with UEFI boot (did I spell it correctly) and Ubuntu 16.04? I am not sure if the technology has changed so that this would be useless.
PS. This backup is meant to be restored this way:
dd if=mbr_63.backup of=/dev/sda bs=512 count=63
man efibootmgr