Hi Simen, I don't know what's going wrong for you, but I followed those instructions two days ago and they worked.
The "writing to file" and "broken pipe" certainly looks like a problem, but I'm not familiar enough with the nix daemon to know how to fix it. FWIW, my nix-channel configuration is slightly different to yours, but I think it resolves to the same thing. $ nix-channel --list nixpkgs https://nixos.org/channels/nixpkgs-unstable I hope that helps, Carlo
