I haven't had an opportunity to test it myself yet, but I've heard very good things about NixOS. The basic premise is that all of your system state, every config file in /etc, every package you have installed, everything, is defined by a single configuration file called configuration.nix. If you back up just your home directory and that file, you can plonk it into a brand new copy of NixOS, run a single command, and have it redownload and re-set-up everything else exactly how you left it.