GRUB is the common boot-loader when using Linux. By default it will select the first entry (primary Linux OS) to boot from. This is sometimes not wanted, for example if a different OS is being used and then want to reboot it remotely. This would cause it to boot it again from the first entry.
The steps below show how to enable the "Save default", remember this needs to be done as the 'root' user.
- Edit /etc/default/grub file, changing GRUB_DEFAULT value to "saved":
GRUB_DEFAULT=saved
- Add (or uncomment) the line:
GRUB_SAVEDEFAULT="true"
- Compile the new GRUB menu:
update-grub2
This is all. On the next boot-up the selection chosen will be save and remembered for the reboot/boot-up that would follow after that.