Easier FS USB Persistent Instructions

Installing mkusb

Open a terminal (Ctrl+Alt+T) and run the following commands one by one:

sudo add-apt-repository universe
sudo add-apt-repository ppa:mkusb/ppa
sudo apt-get update

sudo apt-get install mkusb

The last command might fail (though unlikely) as mkusb (GUI version) has some dependencies that are not preinstalled/active in the live version of Ubuntu.

No need to panic though, the developer has also created a text only version. Run:

sudo apt-get install mkusb-nox

Creating the persistent drive

I will focus on the main GUI version as that is the one I have used. So if you installed the default mkusb (GUI version) run:

sudo -H mkusb /path/to/iso/filename.iso p

For example I have copied my Ubuntu iso to the the home folder, so I type:

sudo -H mkusb ubuntu-16.04-desktop-i386.iso p

The last p parameter tells mkusb that I want a persistent live install. If you omit that you will get a simple live USB.

After you run the command the GUI will open. Follow these steps next:

    Screen 1: Click Select target device
    Screen 2: Double-Click the device you want to install to.
    Screen 3: Double check you have selected the right device. Tick the check-box and click Go.

    Screens 4, 5: Just click quit and let mkusb decide what's best.

    After this mkusb will load some files. Wait patiently till the next input screen.

    Screen 6: Enter the percentage of USB drive space you want to allot for persistence file-system. The remaining will show up as portable storage device.

    Note: Do not enter a value like 100% as some memory will be required for the Ubuntu OS files. Apparently entering 100% now works. As mentioned in @LMB comment, using 100% means the entire USB is used for the OS and the persistent storage

Done!