# Configuring custom start commands with a Procfile on Elastic Beanstalk To specify custom commands to start a Go application, include a file called `Procfile` at the root of your source bundle. For details about writing and using a `Procfile`, see [Buildfile and Procfile](platforms-linux-extend.build-proc.md). **Example Procfile** ``` web: {{bin/server}} queue_process: {{bin/queue_processor}} foo: {{bin/fooapp}} ``` You must call the main application `web`, and list it as the first command in your `Procfile`. Elastic Beanstalk exposes the main `web` application on the root URL of the environment; for example, `http://my-go-env.elasticbeanstalk.com`. Elastic Beanstalk also runs any application whose name does not have the `web_` prefix, but these applications are not available from outside of your instance. Elastic Beanstalk expects processes run from the `Procfile` to run continuously. Elastic Beanstalk monitors these applications and restarts any process that terminates. For short-running processes, use a [Buildfile](go-buildfile.md) command. ## Using a Procfile on Amazon Linux AMI (preceding Amazon Linux 2) If your Elastic Beanstalk Go environment uses an Amazon Linux AMI platform version (preceding Amazon Linux 2), read the additional information in this section. **Notes** The information in this topic only applies to platform branches based on Amazon Linux AMI (AL1). AL2023/AL2 platform branches are incompatible with previous Amazon Linux AMI (AL1) platform versions and *require different configuration settings*. On [July 18, 2022](https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2022年07月18日-linux-al1-retire.html), Elastic Beanstalk set the status of all platform branches based on Amazon Linux AMI (AL1) to **retired**. For more information about migrating to a current and fully supported Amazon Linux 2023 platform branch, see [Migrating your Elastic Beanstalk Linux application to Amazon Linux 2023 or Amazon Linux 2](using-features.migration-al.md). ### Port passing — Amazon Linux AMI (AL1) **Note** The information in this topic only applies to platform branches based on Amazon Linux AMI (AL1). AL2023/AL2 platform branches are incompatible with previous Amazon Linux AMI (AL1) platform versions and *require different configuration settings*. Elastic Beanstalk configures the nginx proxy to forward requests to your application on the port number specified in the `PORT` [environment property](go-environment.md#go-options) for your application. Your application should always listen on that port. You can access this variable within your application by calling the `os.Getenv("PORT")` method. Elastic Beanstalk uses the port number specified in the `PORT` environment property for the port for the first application in the `Procfile`, and then increments the port number for each subsequent application in the `Procfile` by 100. If the `PORT` environment property is not set, Elastic Beanstalk uses 5000 for the initial port. In the preceding example, the `PORT` environment property for the `web` application is 5000, the `queue_process` application is 5100, and the `foo` application is 5200. You can specify the initial port by setting the `PORT` option with the [aws:elasticbeanstalk:application:environment](command-options-general.md#command-options-general-elasticbeanstalkapplicationenvironment) namespace, as shown in the following example. ``` option_settings: - namespace: aws:elasticbeanstalk:application:environment option_name: PORT value: {{}} ``` For more information about setting environment properties for your application, see [Option settings](ebextensions-optionsettings.md).