when creating a tomb make sure the device mapper is loaded among kernel modules
or creation will fail and leave you in the dust.

modprobe dm_mod
modprobe dm_crypt

to create a tomb on a server (even VPS) is possible, but the problem becomes the little
available entropy. in order to fix this one can use EGD the Entropy Gathering Daemon.

on Debian, do:

sudo aptitude install libdigest-sha1-perl
sudo aptitude install ekeyd-egd-linux

/etc/default/ekeyd-egd-linux

wget http://egd.sourceforge.net/

perl ./egd.pl

/etc/init.d/ekeyd-egd-linux start