Rescue System

If your system fails to boot, the "Enable/disable rescue mode" option lets you access the hard drive. 

The rescue environment is powered by Rescatux. Once enabled, boot into it and locate your original hard disk by running:

lsblk

You will see disk devices listed; identify one like /dev/sda1 that matches your drive’s size (for example, 50GB)

After that, mount the device to a directory such as /mnt using the command below:

sudo mount /dev/sda1 /mnt

Make whatever changes are needed

When you are done, disable rescue mode.