Elixir

Railpack builds and deploys Elixir and Phoenix applications with zero configuration.

Detection

Your project will be detected as a Elixir application if a mix.exs file exists in the root directory.

Versions

The Elixir version is determined in the following order:

• Any mise-supported version file (mise.toml, .tool-versions, etc)
• Set via the .elixir-version file
• Detected from the mix.exs file
• Set via the RAILPACK_ELIXIR_VERSION environment variable
• Defaults to 1.18

The OTP version is determined in the following order:

• Any mise-supported version file (mise.toml, .tool-versions, etc)
• Set via the .erlang-version file
• Detected automatically from the resolved Elixir version
• Set via the RAILPACK_ERLANG_VERSION environment variable
• Defaults to 27.3

Configuration

Railpack builds your Elixir application based on your project structure. The build process:

• Installs Elixir and Erlang
• Gets and compiles dependencies using mix deps.get --only prod and mix deps.compile
• If defined, prepares assets using mix assets.setup
• If defined, deploys assets and ecto using mix assets.deploy and mix ecto.deploy
• Compiles a release for the project using mix compile and mix release
• Sets up the start command from your release binary

The selected file will be run with /app/_build/prod/rel/{}/bin/{} start.

Config Variables

Variable	Description	Example
RAILPACK_ELIXIR_VERSION	Override the Elixir version	1.18
RAILPACK_ERLANG_VERSION	Override the Erlang version	27.3