My openSUSE /boot/efi is likely get deleted by me or a fresh installed ubuntu 18.04 or just ge hidden, I couldn't find openSUSE in UEFI and Ubuntu boot menu again. I made a bootable USB with openSUSE-Leap-15.1-NET-x86_64.iso, from it's boot I choose enter "boot from harddisk", then it led me to the openSUSE in my harddisk. I want to know why and it's a secure boot?