grep menuentry /boot/grub2/grub.cfg This will display all your grub entries Highlight the entry you want to default to - for example Windows 7 (loader) (on /dev/sda1) Right click and choose copy Type gedit /etc/default/grub Change the entry GRUB_DEFAULT=0 to GRUB_DEFAULT="Windows 7 (loader) (on /dev/sda1)" i.e. paste the entry you want (including the quotes) Save, then type grub2-mkconfig -o /boot/grub2/grub.cfg
原文：https://www.cnblogs.com/zjhangia/p/10351816.html