```
❯ nix-channel --list
home-manager https://github.com/nix-community/home-manager/archive/release-20.09.tar.gz
unstable https://nixos.org/channels/nixos-unstable
❯ nix-env -f "<unstable>" -iA hellp
error: file 'unstable' was not found in the Nix search path (add it using $NIX_PATH or -I)

```