output of `nix-info` (same for normal user and with `sudo`):
```
system: "x86_64-linux", multi-user?: yes, version: nix-env (Nix) 1.11.15, channels(root): "nixos-17.09.2130.252083ac2c", channels(das-g): "", nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs
```

And there _is_ indeed `/root/.nix-channels`. (My question is whether the non-root user should also have one.)