Grub2 - Community Ubuntu Documentation says the following:
Saving an OS can be achieved by running sudo grub-set-default if DEFAULT=saved is set in /etc/default/grub. It may also be saved if GRUB_SAVEDEFAULT=true is also set in /etc/default/grub. In this case, the default OS remains until a new OS is manually selected from the GRUB 2 menu or the grub-set-default command is executed.
I put the lines
/etc/default/grub, and ran
sudo grub-set-default. Here is the output:
$ sudo grub-set-default entry not specified. Usage: grub-set-default [OPTION] entry Set the default boot entry for GRUB. -h, --help print this message and exit -v, --version print the version information and exit --boot-directory=DIR expect GRUB images under the directory DIR/grub instead of the /boot/grub directory ENTRY is a number or a menu item title. Report bugs to <firstname.lastname@example.org>.
Am I not following the documentation correctly? What's the correct way to do this?