1.usb模块
usbcore
ehci_hcd
uhci_hcd
scsi_mod
usb_storage
sd_mod
libusual
2.usb驱动initrd
mkinitrd --preload=scsi_mod
=sd_mod
=ehci-hcd
=ohci-hcd
=uhci-hcd
=usb-storage
/boot/usb.img
kernel-version //制做一个加载usb盘的initrd
