Yes, that's what I wrote in my last comment, apparently that fdisk won't work at this point, so you have to guess the name of your USB key (try /dev/sda1 or /dev/sdb1) .
Yes, that's what I wrote in my last comment, apparently that fdisk won't work at this point, so you have to guess the name of your USB key (try /dev/sda1 or /dev/sdb1) .