I have a machine with 10 GB of RAM, and I would like to run Ubuntu on it (Debian also OK if its easier), fully in RAM in such a way: I boot from a compressed image on an USB flash disk, that is uncompressed into RAM, and then I can remove the disk from the USB slot, and use the system only with RAM, without any permanent disk.
Whenever I make any changes that I want permanent, I would put the flash disk back into the USB slot (possibly not the same one as I used initially to boot, as I would like to keep many versions of the boot flash disk), and run some command that would save the current state into a compressed image on the disk.
How can I set this up?