The Dockerfile and its entrypoint script work together to set up this container. The key distinction between the two lies in the type of data they store; the entrypoint script typically manages sensitive and frequently changing variables, which are not suitable for Docker's build cache.
The ./drivers directory houses a number of the so-called driver scripts. These scripts are typically accessible from the outside world via Guacamole's SSH connections, and operators can also directly invoke them from within the running instance of this container.