Думаю эта информация будет полезна. Пытался сделать установочную флеш память как пишут в тут, выдавало что-то типа
Attempting to mount media :/dev/sr0
Attempting to mount media :/dev/sda
Attempting to mount media :/dev/sda1
Attempting to mount media :/dev/sda2
Attempting to mount media :/dev/sda5
Attempting to mount media :/dev/sdb1
No Bootable media found. Waiting for new device.
Attempting to mount media :/dev/sr0
Attempting to mount media :/dev/sda
Attempting to mount media :/dev/sda1
Attempting to mount media :/dev/sda2
Attempting to mount media :/dev/sda5
Attempting to mount media :/dev/sdb1
Couldn't find CD to boot, something else is needed
Determining root device...
root block device is unspecified or not detected.
Please specify a device to boot or "Shell" for a shell :>
label gentoo-nofb
kernel gentoo_inst/gentoo
append root=/dev/ram0 init=/linuxrc dokeymap looptype=squashfs loop=/gentoo_inst/gentoo.squashfs cdroot cdroot_marker=ldlinux.sys initrd=gentoo_inst/gentoo.igz
