Many time, you will need to load another operating system than the one you are currently using, just to modify some things on your operating system. The system will then live on your RAM and not on your hard drive.

To do this, you need to prepare a USB key (usually more than 8GB) dedicated for this. You will download the installer of some popular linux distributions that offer this possibility. Here, we will take the example of Ubuntu.

You should download the last version of this OS here.

Follow the instruction here to verify that you downloaded the right software