usb bootable script

gistfile1.txt

MIRROR="distfiles.gentoo.org"
ISO=`wget -q -O - http://$MIRROR/releases/amd64/autobuilds/latest-iso.txt | grep -v \# | sed "s#/.*##"`
wget -N http://$MIRROR/releases/amd64/autobuilds/$ISO/install-amd64-minimal-$ISO.iso
7z e -y install-amd64-minimal-$ISO.iso image.squashfs isolinux/gentoo isolinux/gentoo.igz
read -p "Enter block device to format (blank to skip): " DEV
if ! test -z $DEV; then
[ `id -u` != 0 ] && echo "must be root" && exit 
dd if=/dev/zero of=/dev/$DEV bs=512 count=1 
parted /dev/$DEV mklabel msdos
parted /dev/$DEV mkpart primary 0% 100%
parted /dev/$DEV set 1 boot on
sfdisk -c /dev/$DEV 1 6
mkdosfs -F 16 /dev/"$DEV"1
dd if=/usr/share/syslinux/mbr.bin of=/dev/$DEV
mkdir -p usb
mount /dev/"$DEV"1 usb
cp image.squashfs gentoo gentoo.igz usb
echo '
default gentoo
label gentoo
kernel gentoo
append root=/dev/ram0 initrd=gentoo.igz loop=image.squashfs cdroot
' > usb/syslinux.cfg
touch usb/livecd
umount usb
syslinux /dev/"$DEV"1
fi