UNetbootin is the easiest way to put an bootable Ubuntu ISO onto a USB flash drive.
Using UNetbootin
You must add UNetbootin to Ubuntu before you use it. Install this package: unetbootin
- Insert your USB flash drive
- Run Unetbootin and enter your administrative password.
- Click "..." and find the image you downloaded, start in "Computer", /home/karl/Downloads/ubuntu.iso
- Click "Ok", and wait three minutes.
You're done!