Question: my system doesn't have a hard disk, so I am using a USB stick of 16gb. I am running live ubuntu without installation, it's taking about 3 GB of space. is it possible that can I create a partition for USB so that I can save files in USB when using live ubuntu at the same time?

Answer: 
In at least 18.04 live boot, it permits plugging in a second USB, which shows up promptly. I was then able to drag and drop files from the failing hard drive to the second USB.
Make Sure You *Activated* it Because it Came 0 Gb By default And 0 Means thats the **persistence** is *desactivated*.
There is it.

**strong text**[![enter image description here](https://i.stack.imgur.com/ol85k.png)](https://i.stack.imgur.com/ol85k.png)