Translations:Install Gentoo on a bootable USB stick/54/de
From Gentoo Wiki
LABEL=GENTOO_USB_BOOT /boot ext2 noauto,noatime 1 2
LABEL=GENTOO_USB_ROOT / ext2 noatime 0 1
/dev/SWAP none swap sw 0 0
/dev/cdrom /mnt/cdrom auto noauto,ro 0 0
/dev/fd0 /mnt/floppy auto noauto 0 0