# wipe the disk
wipefs –a /dev/sda
parted /dev/sda mklabel gpt
parted /dev/sda mkpart logical ext4 0% 100%
mkdir /mnt/usb
cryptsetup luksFormat /dev/sda1                   # type YES and then enter a password
dd if=/dev/urandom of=/root/keyfile bs=1024 count=4
chmod 0400 /root/keyfile
cryptsetup luksAddKey /dev/sda1 /root/keyfile     #Enter passphrase
cryptsetup open /dev/sda1 encrypted
# create new ext4 filesystem
mkfs.ext4 /dev/mapper/encrypted
echo encrypted /dev/sda1 /root/keyfile luks >> /etc/crypttab
echo /dev/mapper/encrypted /mnt/usb ext4 defaults 0 2 >> /etc/fstab
mount /mnt/usb
# depending on your system, you may need to update your initramfs at this point
reboot