Le 08/07/2017 à 20:10, Sebastian Luna Valero a écrit :
I have a dual-boot laptop with Ubuntu 12.04 LTS and Windows 7. I am planning to install the latest Debian 9 LTS on the partition where Ubuntu is currently installed.
Note that Debian 9 is not yet LTS and won't be before a long time.The current LTS is Debian 7 "Wheezy". A release eventually becomes LTS only after normal support has ended, one year after becoming oldstable.
Since grub is already available on the laptop, does anyone know what will happy when I install grub again with Debian?
It depends where Ubuntu installed GRUB, and where Debian will install it. Anyway, some parts of GRUB are in /boot, so GRUB must be reinstalled if you're going to wipe /boot.