I want to install Ubuntu on a USB drive and found these instructions here.
I want to do this, because I want to use my laptop when I am in a car or when I walk. So, I want to turn off my hard drive when booting from USB to prevent it to cause bad sectors, etc.
Now my question is: how to manually turn off the hard drive when booting from USB? Or, does it turn off when isn't in use or being mounted?