Let me share with you about this exciting subject.  Having Linux (I use Slackware Linux) on a USB drive has changed the way that I use computers.  Now the drives that I use are more often outside of the computer's box than inside of it.  This allows great flexibility.  I am no longer tied to one set of hardware.

So how does it work?  Well, "Linux on a USB Drive" is just Linux installed to a hard drive or solid state drive (SSD).  (10-02-21: I have learned that you can even install Linux to a USB 3.0 flash drive--it works!)

The Linux O.S. on the hard drive or SSD needs boot instructions to boot and run.  There are many variations on how to provide these boot instructions, but there are just two ways (booting from a CD and from the boot record of a hard drive) that I use currently in my Rosevear Software products.  The CD, by the way, that is used to boot from one of my hard drives is called "Joe's Boot Disk" or "JBD".  Click here to read about JBD on the Rosevear Software website.

I have just recently (today is 8-17-10) learned how to make USB drives boot the other way (from the boot record), so it is new to me.  My first impressions are that this is a great way to boot Linux, because you don't need anything else like JBD, but that's the end of the advantages.  The down side to booting this way is that it only works on computers that have a BIOS that is capable of being configured to do this.  Also I found that the configuration of the BIOS to do this is not always clear.