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Rails with Nix

I like having all the Nix stuff in a ./nix folder, so shell.nix is just symlinked to the one in there.

There's no need to directly run bundle install or bundle exec with this setup, but since a gemset.nix file is needed, use the nix/bundle wrapper script if you need to add/upgrade gems.

You probably want to install these:

  • lorri - it makes nix-shell much faster due to caching
  • direnv - required by lorri for autoloading
  • niv - simplify nix sources


Eventually you'll want to switch to a different nix channel, or add another. Niv makes it easy:

niv update nixpkgs -b nixos-20.03 # point the nixpkgs source to the current stable release
niv add NixOS/nixpkgs-channels -n unstable -b nixos-unstable # add the development channel


Bundix is not yet able to handle every Gemfile -- gems on local paths and architecture-specific gems might still have some problems.

If you make changes and they don't seem to update in the current shell, try running nix-shell or lorri shell to rebuild the environment manually.

I haven't really explored generating Docker images for deployment via Nix, but Christine Dodrill has a pretty good intro to doing this with Rust.


Example Rails 6 app using nix for dependencies






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