Create Sqlite DB with mix releases and docker

Hello,

i am trying to deploy a phoenix 1.6 application and following the official recommendations and Dockerfile about deploying with releases in a docker container.

Because mix is not available in the final image after the release was build i cant figure out a way to create the database. I tried to create and modify the recommended Release module (inspired by the mix ecto.create task) but Exqlite fails with {:error, :database_open_failed}.

Here is my release module (i changed it back to MyApp)

defmodule MyApp.Release do
  @app :my_app

  def migrate do
    load_app()

    for repo <- repos() do
      {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :up, all: true))
    end
  end

  def create do
    load_app()

    for repo <- repos() do
      repo.__adapter__.storage_up(repo.config)
    end
  end

  def rollback(repo, version) do
    load_app()
    {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :down, to: version))
  end

  defp repos do
    Application.fetch_env!(@app, :ecto_repos)
  end

  defp load_app do
    Application.load(@app)
  end
end

I try to execute it with eval "MyApp.Release.create"

The command fails with

web_1  | ** (MatchError) no match of right hand side value: {:error, :database_open_failed}
web_1  |     lib/ecto/adapters/sqlite3.ex:422: Ecto.Adapters.SQLite3.storage_up_with_path/2

Is there a better way to create the database or has anybody a solution for my problem? Is it because the elixir user in the final container has not the necessary permissions to create the file? How to work around that?