Boot loaders and boot managers.

Grub, rEFInd.

Grub Boot

Boot can be in MBR or UEFI mode.

If grub is not installed, install it with grub2-install /dev/sda. When changing grub2 options in /etc/default/grub, recreate grub config by running

grub2-mkconfig -o /boot/grub2/grub.cfg


UEFI boot requires a /boot/efi partition, knows as EFI System Partition (ESP). ESP is vfat, 500MB, mounted at /boot/efi as recommended by openSuse installer.


Once the partition is created, install grub on it.


To mount a drive from rescue USB, see here.

Also see this for boot troubleshooting.