Hello Friends,
In this article we’ll see 3 way of installing Ubuntu on a USB drive.
We’ll see how to create a live USB Ubuntu disk, just like your live CD.
Only difference is that we’ll be booting and installing Ubuntu using
this live USB diskette, and as last option how to do a full installation
of ubuntu on your USB drive.
Option 1: Boot Ubuntu as a Live CD from a USB Flash Drive
Use this option to install Ubuntu as a Live Install, which allows you
to boot from the USB flash drive in Ubuntu, experience the Linux
environment but will not retain any changes or settings after you shut
down. This is a great way to get a feel for the OS, test some of it’s
capabilities as well as typical hardware compatibility.
Read more :-
http://blog.ask4itsolutions.com/2010/10/11/3-ways-to-boot-ubuntu-linux-from-a-usb-flash-drive/