Environment Variables

Some parts of the build can be configured with environment variables. These are often prefixed with RAILPACK_.

Build Configuration

Variables that impact build configuration are not read from the process environment and must be specified explicitly with --env when using the Railpack CLI.

Name	Description
RAILPACK_BUILD_CMD	Set the command to run for the build step. This overwrites any commands that come from providers
RAILPACK_INSTALL_CMD	Set the command to run for the install step. This overwrites any commands that come from providers. All files are copied to the root of the project before running the command.
RAILPACK_START_CMD	Set the command to run when the container starts
RAILPACK_PACKAGES	Install additional Mise packages. In the format pkg[@version]. The version is optional; if not provided, the latest version is used. Allows list.
RAILPACK_BUILD_APT_PACKAGES	Install additional Apt packages during build. Allows list.
RAILPACK_DEPLOY_APT_PACKAGES	Install additional Apt packages in the final image. Allows list.
RAILPACK_DISABLE_CACHES	Disable cache mounts defined in the top-level caches map, or * for all. Allows list. Layer caching is unaffected.

Variables which allow a list use space-separated values. For example:

railpack build --env 'RAILPACK_PACKAGES=pipx:httpie jq@latest' .
railpack build --env 'RAILPACK_DISABLE_CACHES=gradle maven' .

To configure more parts of the build, it is recommended to use a config file.

Global Options

These environment variables affect the behavior of Railpack:

They are read directly from Railpack’s process environment; do not pass them with --env.

Name	Description
FORCE_COLOR	Force colored output even when not in a TTY
RAILPACK_VERBOSE	Enable verbose logging (equivalent to the --verbose flag)