Skip to content

Dockerfile Deployment

New

Introduced in 0.3.15

While Dokku normally defaults to using heroku buildpacks for deployment, you can also use docker's native Dockerfile system to define a container.

To use a dockerfiles for deployment, commit a valid Dockerfile to the root of your repository and push the repository to your Dokku installation. If this file is detected, Dokku will default to using it to construct containers except in the following two cases:

  • The application has a BUILDPACK_URL environment variable set via the dokku config:set command or in a committed .env file. In this case, Dokku will use your specified buildpack.
  • The application has a .buildpacks file in the root of the repository. In this case, Dokku will use your specified buildpack(s).

Exposed ports

By default, Dokku will extract the first EXPOSE tcp port and use said port with nginx to proxy your app to that port. For applications that have multiple ports exposed, you may override this port via the following command:

# replace APP with the name of your application
dokku config:set APP DOKKU_DOCKERFILE_PORT=8000

Dokku will not expose other ports on your application without a custom docker-option.

If you do not have a port explicitly exposed, Dokku will automatically expose port 5000 for your application.

Customizing the run command

By default no arguments are passed to docker run when deploying the container and the CMD or ENTRYPOINT defined in the Dockerfile are executed. You can take advantage of docker ability of overriding the CMD or passing parameters to your ENTRYPOINT setting $DOKKU_DOCKERFILE_START_CMD. Let's say for example you are deploying a base nodejs image, with the following ENTRYPOINT:

ENTRYPOINT ["node"]

You can do:

dokku config:set APP DOKKU_DOCKERFILE_START_CMD="--harmony server.js"

To tell docker what to run.

Setting $DOKKU_DOCKERFILE_CACHE_BUILD to true or false will enable or disable docker's image layer cache. Lastly, for more granular build control, you may also pass any docker build option to docker, by setting $DOKKU_DOCKER_BUILD_OPTS.