> But not the "Nix system config manager", which is grouped under the same set of CLI tools, is that right? The `nixos-rebuild` command is what you'd use to ap

> But not the "Nix system config manager", which is grouped under the same set of CLI tools, is that right? The `nixos-rebuild` command is what you'd use to apply a NixOS configuration (that's NixOS only). (I believe it's possible to run the command to build a configuration on non-NixOS). Whereas, the other nix CLI programs are mainly `nix-build`, `nix-shell`, etc. which are now grouped under a single `nix` command. > Packages or system configuration or both? I'd say packages. That people like NixOS for its declarative system configuration is incidental. Nix's key idea is symlinking everything. You put a package in some directory under /nix/store, where the address is computed from that package's inputs. (e.g. what compiler to use, what compiler flags to use). If you build the same package with different inputs (e.g. different compiler versions), these packages can exist alongside each other in /nix/store. Nix can then build a PATH using whichever package you want to use. It's able to come up with ~/.nix-profile/bin and ~/.nix-profile/include (and share, etc.), symlinking to the stuff in /nix/store. NixOS essentially 'just' applies that idea, but symlinks stuff under /etc to whatever /nix/store package has the system configuration. (Plus uses systemd services, and a few other things). e.g. when I `readlink /etc/hosts`, it resolves to `/nix/store/n5ijm9zzkcm7qglsqrfvnixih0q7dskb-host`, or /etc/fstab to /nix/store/xb7jmzd0wy0wy4vihh0q17m81kmqgc7y-etc-fstab.