"Tin Hat is a Linux distribution derived from hardened Gentoo
which aims to provide a very secure, stable and fast Desktop
environment that lives purely in RAM.
"Tin Hat boots from CD, or optionally a pen drive, but it is not
a LiveCD. It does not mount any file system from CD via unionfs or
otherwise. Rather, Tin Hat is a massive image (approx. 2.3GB) which
loads into tmpfs upon booting."