Quick'n'Dirty how to make a LUKS encrypted disk partition.
I'm encrypting the first partition on the disk called hdc.
Make luks device:
cryptsetup -y --cipher aes --key-size 128 luksFormat /dev/hdc1
If you choose to use sha256 instead, you will get something like this:
Failed to setup dm-crypt key mapping. Check kernel for support for the aes-cbc-essiv:sha256 cipher spec and verify that /dev/hdc1 contains at least 133 sectors.
This is because you're using the geode_aes kernel module which only support sha128. You can get it to “eat” a sha256 but you will have to unload geode_aes (sudo rmmod geode_aes) and load the generic aes module (sudo modprobe aes). There is however a speed penalty when doing it like this. I don't know why though, maybe there is some hardware acceleration involved when using the geode_aes module. If you play with Truecrypt you will also see some errors related to this problem. You can probably get it working using a sha128 but I haven't spent time figuring it out.
Open the LUKS:
cryptsetup luksOpen /dev/hdc1 encdisk
Make filesystem:
mkfs.ext3 -j -m 1 -O dir_index,filetype,sparse_super /dev/mapper/encdisk
Mount device for use:
mount /dev/mapper/encdisk /share/encrypteddisk01
Unmount device:
umount /share/encrypteddisk01 cryptsetup luksClose encdisk