So... Nix is just a package manager, but it's a package manager that tries to be as generic as possible and only have the attitude that a "package" is just "a b

So... Nix is just a package manager, but it's a package manager that tries to be as generic as possible and only have the attitude that a "package" is just "a bunch of (immutable) files that depend on the presence of another bunch of files" and so should be able to take over the job of all package mangers on your system (no matter how much of a special snowflake language x or application y thinks it is and deserves its own, inevitably crappy, package manager). One of the many advantages this brings is that your system's software installation makes sense "as a whole" and isn't the result of 7 different package managers or "auto updating" applications fighting each other. But because of this, Nix can only have things depend on packages it has provided itself. It doesn't assume anything about the host system apart from the kernel. So yes, installing Nix on an existing Linux system can feel like installing another distribution. But you only ever have to use as much of it as you want to. Everything lives in /nix, and to get rid of everything you just have to `rm -rf /nix`. NixOS is a full distribution that just uses Nix for everything, including configuration management.