Restore Grub 2 After Installing Other OS

This article is just a note to bring back the bootloader after installing other operating systems that resulted in the loss of the bootloader Grub 2, This is the way commonly used :

Boot with bootable CD or USB for repair your GRUB2
See location of the linux partition
root@bt ~# fdisk -l

nb :

* Note the type of your partition. Usually the linux partition type is ext4, ext3, etc.

Mount this partition
sudo mount /dev/sda7 /mnt
sudo mount --bind /dev/ /mnt/dev
sudo mount --bind /proc/ /mnt/proc/

nb :

* sda7 = your partition linux.. it fdisk -l was. Change sda7 became the location of your linux partition.

Chroot to this mounting
sudo chroot /mnt/

Update Grub for repair your Grub
update-grub2

Fit the new GRUB in the MBR :
grub-install /dev/sda

Finish and Reboot Your System