1. Go to the following URL: http://unetbootin.sourceforge.net/ and download the file
2. Make the file executable (chmod +x file_name)
3. This step is specific for Ubuntu: If you receive the message “7z not found ….”, open a terminal and run “sudo apt-get install p7zip-full“

BTW, if you need to write IMG files instead on Ubuntu, you can install the USB image writer by running “sudo apt-get install usb-imagewriter”

Enjoy 🙂