hiding grub bootloader

open up your /etc/default/grub :

sudo nano /etc/default/grub

and change the GRUB_TIMEOUT to 0 and add the GRUB_HIDDEN_TIMEOUT_QUIET=true after it.

now update the boot-loader :

sudo update-grub

now after rebooting you won't see the grub menu , just a simple graphical verbose which indicates which kernel version is being loaded .