This requires adding the following to hydra.conf: binary_cache_key_name = <key-name> binary_cache_private_key_file = <path-to-private-key> e.g. binary_cache_key_name = hydra.nixos.org-1 binary_cache_private_key_file = /home/hydra/cache-key.sec
This reverts commit 190bffd846f044a13c239513f8ef1ea45ee8a1f2.
Fixes <https://github.com/NixOS/hydra/issues/102>.