Is it possible to switch to running Linux from RAM or RAM disk after starting starting initially from disk?

eg. You need to make an image of your hard disk, FTP it to a remote location, some time later you want the image back, so you start the system from disk as usual, restore the image you FTP'd from the remote location back into place.

More like a CloneZilla backup and restore, without booting the server from CD or USB disk, but starting from the normal hard disk?

**Notes on environment**
I should have mentioned it earlier. It is a remotely hosted VM where I cannot boot into a recovery console mode or do a netinstall. It will always boot onto the same disk. Which means that if there is some serious corruption I can't repair it offline, which is why being able to ftp a previously saved backup into place is so important