Docker image seems to be missing commands: `nixos-rebuild`, `systemctl`

[nhooey]

Why does the nixpkgs/nix-unstable Docker image not have nixos-rebuild or systemctl?

$ docker run --tty --interactive nixpkgs/nix-unstable
bash-5.2# nixos-rebuild
bash: nixos-rebuild: command not found
bash-5.2# systemctl
bash: systemctl: command not found
bash-5.2#

Even if that's expected for nixpks/nix-unstable, would you know why it's also the case for nixos/nix, which might be intended as a full NixOS install?

(I'm not sure what the difference between these images are, or what their intended for.)

I asked similarly on Stack Overflow:

• Why do some official Nix Docker containers not have the nixos-rebuild command?

[zimbatm]

It's a bit confusing but the container image are shipping the Nix binary. This is only the language and package manager of the full NixOS distribution.