WombatWiki

sudo apt-get inastall cryptsetup

sudo cryptsetup -v --cipher aes-xts-plain64 --key-size 512 --hash sha512 --iter-time 5000 --use-random luksFormat /dev/sdaX
sudo cryptsetup luksOpen /dev/sdaX container

sudo fdisk -l

Disk /dev/mapper/container: 2054 MB, 2054190592 bytes
. . .
Disk /dev/mapper/container doesn't contain a valid partition table

sudo dd if=/dev/zero of=/dev/mapper/container

sudo mkfs.ext4 /dev/mapper/container
sudo cryptsetup close container

sudo cryptsetup luksOpen /dev/sdaX container
sudo mount /dev/mapper/container /mnt/tmp/

sudo umount /mnt/tmp
sudo cryptsetup luksClose container

https://wiki.archlinux.org/index.php/Dm-crypt/Encrypting_a_non-root_file_system