Se você desabilitar muitos dos módulos relacionados a SCSI, é muito provável que você não possa mais inicializar a partir de dispositivos USB.
especialmente:
CONFIG_SCSI:
If you want to use a SCSI hard disk, SCSI tape drive, SCSI CD-ROM or
any other SCSI device under Linux, say Y and make sure that you know
the name of your SCSI host adapter (the card inside your computer
that "speaks" the SCSI protocol, also called SCSI controller),
because you will be asked for it.
You also need to say Y here if you have a device which speaks
the SCSI protocol. Examples of this include the parallel port
version of the IOMEGA ZIP drive, USB storage devices, ...
read <file:Documentation/scsi/scsi.txt>.
The module will be called scsi_mod.
However, do not compile this as a module if your root file system
(the one containing the directory /) is located on a SCSI device.
e
CONFIG_BLK_DEV_SD:
If you want to use SCSI hard disks, Fibre Channel disks,
Serial ATA (SATA) or Parallel ATA (PATA) hard disks,
USB storage or
Você deve verificar sua configuração lá.