On Wed, 1 Jun 2016 13:56:41 +0200
Adam Borowski <kilobyte@???> wrote:

> A more user-friendly way is "grub-reboot" for one-shot, and
> "grub-set-default" for changing the default permanently.

Interesting, I wasn't aware of that command - nevertheless, you still
have to edit /etc/default/grub to contain "GRUB_DEFAULT=saved".
Apparently, the command then saves the default to the file
/boot/grub/grubenv.

In both cases, if the default boot entry has to to be persistent over
kernel upgrades, the "menu item title" has to be used instead of a
plain number to define the menu entry.

Florian