There are many ways for backing up data stored into your hard drive under Ubuntu. You may use software to protect your data from being lost or get corrupted, or you can simply use some terminal commands for making a copy of your computer data.
In this tutorial we will resort to the terminal to create a full ISO copy of your hard drive under Ubuntu with just a single command, no need to install and use third-party programs. The command will create an ISO image of your hard drive so that you can burn it into a DVD or move it to an external hard drive, for example.
Open the terminal (Ctrl+Alt+T) and run this command to create an ISO copy of your hard drive:
sudo dd if=/dev/sda of=file.iso
Your hard disk will be saved into an iso file having the name "file.iso" in the current folder. If your hard drive is not /dev/sda, then correct it with your own. Here is another command having the same effect:
sudo cat /dev/sda > ~/file.iso
[Note]: To interrupt the iso file creation, you can simply press Ctrl+C.