NixOS is aiming for the same goal, I believe. NixOS is built on top of different package manager, Nix.
With aptly you're still using your favorite Debian/Ubuntu distro, installing packages with apt-get and so on.
With aptly you're still using your favorite Debian/Ubuntu distro, installing packages with apt-get and so on.
At the moment, you'd have to use an external configuration management system for actually defining your systemd services, etc.
One thing missing from Nix is ability to store passwords and the like in the nix store, and from what I understand this applies to NixOS as well as using Nix outside NixOS. For example, every file in the nix store is world readable.