Hi, I've decided to delve in to the world of linux as I've never touched it before and thought it would be good to try out Ubuntu. Unfortunately, I've never used it before and I currently don't have access to DVDs to burn an image, so I was hoping to boot it from a USB. I've followed these instructions


And I've install rEFit, but when I've attempt to selected the usb drive after I've rebooted, it will take me to a command screen that says

'Uknown filesystem '
grub rescue

Did I miss something? Is there anyone who could help me out?