grub - configuration file

How do I set the grub timeout and the grub default boot entry?

https://askubuntu.com/questions/148095/how-do-i-set-the-grub-timeout-and-the-grub-default-boot-entry

first change this file

sudo vi /etc/default/grub

parameter :

for showing log : 

GRUB_CMDLINE_LINUX_DEFAULT : remove the parameters quiet and splash.

and after update grub

update grub : will search all OS partition existing on disk, and add an entry for each one !

sudo update-grub

reboot

reboot