How to modify waiting time of the dual boot menu(修改双系统启动等待时间)

link: https://askubuntu.com/questions/711062/how-to-modify-waiting-time-of-the-dual-boot-menu

Open a terminal window, then back up the existing grub config file:

sudo cp /etc/default/grub /etc/default/grub-backup

Now (using sudo or gksudo depending on your editor of choice) edit /etc/default/grub and change the number in this line of the file

GRUB_TIMEOUT=10

to your desired waiting time in seconds.

Exit, saving the file, and then run

sudo update-grub

On your next boot you should have the wait time you specified.