Reinstalling the GRUB Boot loader on Linux.

We can recover a corrupted or mistakenly deleted Grub Boot loader using the rescue mode :

1. Boot the system from any boot installation media like a CD-Rom or a Flash Drive, etc.

2. Use the linux rescue command as shown below at the installation prompt to enter the rescue environment:

# Linux rescue

3. Type the below command to mount the root partition:

     # chroot /mnt/sysimage

4. Type the below command to re install the Grub Boot loader, Where /dev/sda is the boot partition:

     # /sbin/grub-install /dev/sda

5. Go through the /boot/grub/grub.conf file once again, as additional entries may be needed for GRUB so as to make any custom changes there (like controlling another installed operating system)

Step 6. Finally, reboot the system

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