Since `grub2-mkconfig` (and *os-prober*) cannot estimate which operating system, of those it finds, is to be marked as default, we usually are unable to predict the order of the entries in `/boot/grub2/grub.cfg`. To change the default layout, we need to set the default based on the `name` or `title`.
. Regenerate the *GRUB2* configuration file and reinstall the bootloader into the MBR, as described in link:#adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].
If you understand the risks involved, you can manually modify the `/boot/grub2/grub.cfg` file. In that case, set the number of the default operating system using the `set default` variable.