[Nix-dev] Setting binary-cache doesn't work (was: Merging x-updates?)

[Peter Simons]

Hi Eelco,

 > Use "--option binary-caches http://hydra.nixos.org" to get prebuilt
 > binaries from Hydra.

this doesn't work for me:

  $ nix-env --option binary-caches http://hydra.nixos.org -u \* --always
  [...]
  error: substituter
  `/nix/store/96rgql0340rc6vyrwrb0p5jd7j9q017h-nix-1.2pre2910_b674665/libexec/nix/substituters/download-from-binary-cache.pl'
  failed: binary cache ‘http://hydra.nixos.org’ is not trusted (please add
  it to ‘trusted-binary-caches’ [http://nixos.org/binary-cache
  http://nixos.org/binary-cache] in /etc/nix/nix.conf)

The appropriate options are set in /etc/nix/nix.conf, though:

  $ cat /etc/nix/nix.conf
  # WARNING: this file is generated.
  build-users-group = nixbld
  build-max-jobs = 4
  build-use-chroot = true
  build-chroot-dirs = /dev /dev/pts /proc /bin /nix/store/043zrsanirjh8nbc5vqpjn93hhrf107f-bash-4.2-p24 /nix/store/27116bbxhi8dd7l2fjjfbwj6p35ql7n7-readline-6.2 /nix/store/4gv9gby4bn1y0rlw3k0d5lyqy0yfkrc6-gcc-4.6.3 /nix/store/ahg5mlj2mlp7yfl3x875pq95ar763vgj-ncurses-5.9 /nix/store/cj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13 /nix/store/i3mqzy76lf51v5zqxjxyvf11j25iwycd-zlib-1.2.7 /nix/store/jfcs9xnfbmiwqs224sb0qqsybbfl3sab-linux-headers-2.6.35.14 /nix/store/qvs2rj2ia5vci3wsdb7qvydrmacig4pg-bash-4.2-p24
  gc-keep-outputs = true
  build-cores = 6
  binary-caches = http://nixos.org/binary-cache http://hydra.nixos.org
  trusted-binary-caches = http://nixos.org/binary-cache http://hydra.nixos.org

Just out of curiosity: how does the binary cache at
http://nixos.org/binary-cache differ from http://hydra.nixos.org?

Take care,
Peter