Set a Start Command

A start command is the process used to run a Deployment's code, for example python main.py or npm run start.

Railway automatically configures the start command based on the code being deployed, see Build and Start Commands for more details

Configure the Start Command

When necessary, start commands may be overridden, like for advanced use-cases such as deploying multiple projects from a single monorepo.

When specifying a start command, the behavior depends on the type of deployment:

Dockerfile / Image: the start command overrides the image's ENTRYPOINT in exec form.

If you need to use environment variables in the start command for services deployed from a Dockerfile or image you will need to wrap your command in a shell -
```
/bin/sh -c "exec python main.py --port $PORT"
```
This is because commands ran in exec form do not support variable expansion.
Nixpacks: the start command is ran in a shell process.

This supports the use of environment variables without needing to wrap your command in a shell.