[Nix-dev] How to upgrade when Nix is too old to evaluate nixpkgs

[Bjørn Forsman]

Hi all,

I picked up an old NixOS installation from 2013, with nix 1.5.3. I
tried to upgrade to NixOS 16.03:

  $ nixos-rebuild build
  ...
  error: evaluation aborted with the following error message: `This
version of Nixpkgs requires Nix >= 1.10, please upgrade! See
https://nixos.org/wiki/How_to_update_when_Nix_is_too_old_to_evaluate_Nixpkgs'

The wiki page suggests to download something from hydra that now
yields a 404 error. I know the wiki is in read-only mode and NixOS
documentation generally needs work, so I check hydra myself to find
the correct URL:

  http://hydra.nixos.org/build/37216316

The problem is that none of the build artifacts can be downloaded!
Every URL return a 404 error saying:

  Path /nix/store/hmd2dzzsfan51snxgfy3ngmid5rvf08s-nix-1.11.2-debug is
no longer available.

(Going to builds a few weeks/months back gives the same error, just a
different hash.)

Suggestions?

Best regards,
Bjørn Forsman