Recommended directory to save other files

Hello there, I tried to find an answer for this question but couldn’t find it anywhere, so here it goes!

We have a project composed by some docker images, one of them containing an Elixir application inside. During development, Mix and all the test tooling is made available for the developer. In production, a minimal image is deployed containing just the release (BTW, releases are a killer feature of Elixir/Erlang, I love it!)

Now we have dependency on a file (which happens to be a certificate) that has to be mounted during development (the certificate gets always rotated, for testing purposes) and has to made available to the release in production, either shipped with the container image or mounted by another mechanism at a known and predefined (or configurable) location.

So, the question: is there any recommended way to make this kind of static file-based asset available to the Elixir (or Erlang) runtime? Where should static assets be placed? I’m aware that I can put it pretty much anywhere I want, but is there any good practice to be followed, among the other directories like lib, deps, etc?

Thanks in advance!

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I typically use priv/assets. Erlang comes with :application.priv_dir/1 I think? (I’m on my phone so can’t check) which will accurately track it through releases.


Yep use priv, it’s built into the release by default. Then you can use :code.priv_dir(:your_app) or Application.app_dir(:your_app, "priv") to get its path, which will work in both development and release. Of course, it won’t help if you want your file to be placed after you build the release (in which case you could place it in the directory manually but you could put it anywhere else in the filesystem too and it’s up to you).


There are also Overlays for mix release. Maybe it can also help.

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thanks for the correction! I knew my memory was fishy.

Thanks for all the suggestions. This was waaaay more useful than I was expecting! Both solutions (priv directory and release Overlays) sound really solid. I’ll try them both and follow up this thread with what worked the best.