The first thing we are going to do is dd the Gentoo OS onto a USB. Download the Gentoo minimal ISO HERE. Alternatively, you can boot off of a Live CD but the focus surrounding this write up will focus on a Live USB medium.
I prefer Gentoo as a live OS but that doesn't mean you have to use Gentoo too. The OS(operating System) does however need to be in ISO format! Which ever OS you chose, you need to DD the ISO to the newly formatted USB drive.
NOTE Each mentioned command should be clickable and will take you to it's manpages. Any word highlighted in blue should be clickable unless its background is grey.
Let's plug in our 2GB USB drive and find it with fdisk