Shentrypoint

Shentrypoint is a script that provides an easy way to debug your Docker applications without getting in your way. Shentrypoint does run as PID 1, but it doesn't aim to be a full init process.

Guiding Principles

1. When your container starts, your application should start
2. When your application dies, your container should die
3. When you send control signals to your container, your application process should receive them
4. When you send SIGINT (CTRL+C) to your container, you should get a shell prompt (not a stopped container) as if you'd been running your application process in the foreground from a shell all along

Why?

We put together a lot of automation around running containers in terms of configuration for inputs, network, volumes, etc, not to mention connecting these containers to other systems in a deployment. Sometimes, the easiest way to get a debugging environment is to take over an existing container. Shentrypoint makes it possible to docker attach to an existing container and you can pretend you had launched the application as a foreground process all along. You can hit CTRL+C, modify your container's filesystem, run arbitrary commands, restart your application and debug it interactively.

How to Use It

1. Create a Procfile where the keys are the command words you want to run later
2. Add shentrypoint to your docker image
3. Add ENTRYPOINT /path/to/shentrypoint to your Dockerfile

Use the command words defined in your Procfile to run your containers