grub-editenv

Edit GRUB environment variables. More information: https://www.gnu.org/software/grub/manual/grub/grub.html.

grub-editenv /boot/grub/grubenv set default=Ubuntu

grub-editenv /boot/grub/grubenv list timeout

grub-editenv /boot/grub/grubenv unset saved_entry

grub-editenv /boot/grub/grubenv list kernel_cmdline