point $NIX_PATH to ~/.nix-defexpr/channels I would like to point `$NIX_PATH` to `~/.nix-defexpr/channels` instead of `~/.nix-defexpr/channels_root` as currently. I don't want to have to type that every time I run `nix-env`. What's the right way of doing that?

I would simply define the variable the way you want it in your `~/.profile`.