A system administrator needs to ensure that a recently installed kernel appears in the boot menu. The GRUB2 bootloader is used, and the administrator has copied the new kernel image to /boot. Which of the following commands should be executed to regenerate the GRUB2 configuration so that the new kernel will be listed at boot time?
mkinitrd
grub2-mkconfig -o /boot/grub/grub.cfg
grub2-mkconfig --refresh
update-grub