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== Should I use http://hydra.nixos.org/ as a binary cache? ==
== Should I use http://hydra.nixos.org/ as a binary cache? ==


Short answer: no.
No. As of 2017, all build artifacts are directly pushed to http://cache.nixos.org/ and are available there, therefore setting http://hydra.nixos.org/ as a binary cache no longer serves any function.
 
http://cache.nixos.org is hosted on AWS S3, so it is fast and efficient, but it only contains binaries for nix channels (''nixos-unstable'', ''nixpkgs-unstable'', and some stable channels too).
 
So, if the channel is way behind, you may see recommendations to add http://hydra.nixos.org/ as a binary cache, as it contains all recent builds, including ones not pushed to channels.
 
Unfortunately, due to poor caching, http://hydra.nixos.org/ needs to calculate what is available ''every time'' you ask about substitutes, so using it regularly as a cache will slow down the build machines.
 
Thus, the recommended configuration is to '''not''' put http://hydra.nixos.org/ in any config file or automated script. But if you are working on nixpkgs master, then the binary cache provided by Hydra can be very helpful. In such a case, you can add the Hydra cache to the trusted binary caches in nix.conf or configuration.nix, restart the Nix daemon, and use <code>--option extra-binary-caches http://hydra.nixos.org/</code> in whatever commands are convenient.


== I'm trying to install NixOS but my Wifi isn't working and I don't have an ethernet port ==
== I'm trying to install NixOS but my Wifi isn't working and I don't have an ethernet port ==