"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."