Enable LUKS disk encryption with a key file

enable-luks-howto

# Create strong LUKS key
openssl genrsa -out /root/luks.key 4096
chmod 400 /root/luks.key

# Fill random data to the device
shred -v --iterations=1 /dev/xvdb 

# Format device
echo "YES" | cryptsetup luksFormat /dev/xvdb --key-file /root/luks.key 

# Open device
cryptsetup luksOpen /dev/xvdb data1 --key-file /root/luks.key 

# Format device
mkfs.ext4 /dev/mapper/data1

# Mount
mount /dev/mapper/data1 /data1

# Persist at boot
Add to /etc/crypttab: data1 /dev/xvdb /root/luks.key luks
Add to /etc/fstab: /dev/mapper/data1       /data1  ext4    defaults 1 2

# Restore default SELinux contexts:
/sbin/restorecon -v -R /data1

# Verify
cryptsetup -v isLuks /dev/xvdb
df -h /data1

Thanks for the script.

echo "YES" | cryptsetup luksFormat /dev/xvdb --key-file /root/luks.key

You can also do:
cryptsetup -q luksFormat /dev/xvdb --key-file /root/luks.key

Just to make it a bit more reliable.