GRUB 2

Config
/etc/boot/grub2/grub.cfg

Save Default
/etc/default/grub GRUB_DEFAULT=saved GRUB_SAVEDEFAULT=true

Quick update: echo "GRUB_SAVEDEFAULT=true" >> /etc/default/grub grub2-mkconfig -o /boot/grub2/grub.cfg

References:
 * dual boot - How to get grub2 to remember last choice? - Ask Ubuntu - http://askubuntu.com/questions/148662/how-to-get-grub2-to-remember-last-choice

Chain Loader
menuentry "Fedora (chainload)" { savedefault insmod ext2 insmod chain set root=(hd0,msdos1) chainloader +1 }

Disable OS Prober
echo "GRUB_DISABLE_OS_PROBER=true" >> /etc/default/grub grub2-mkconfig -o /boot/grub2/grub.cfg