Traditionally kernels were numbered starting from 0 but by default the "new style" of grub boot loading considers each subkernel item to be different so if you have 3 entries for 4.40-148 rather than counting for 1. To get the expected behavior let's show this example and how we can boot it We do a grep on menuentry in /boot/grub/grub.cfg to see all of the bootable kernels rather than scrolling through loads of extra entries we don't care about (thou........