What signal is typically sent to stop a running Docker container?

The signal that is typically sent to stop a running Docker container is SIGTERM. When you issue a command to stop a container using docker stop, Docker sends the SIGTERM signal to the main process running in that container. This signal is part of a graceful shutdown approach; it allows the application running inside the container to clean up resources and exit safely within a specified timeout period.

Using SIGTERM is important because it gives the process the opportunity to finish ongoing tasks or save its state before it is terminated. If the process does not terminate within the timeout period, Docker will then send a SIGKILL signal to forcefully stop the container, ensuring it is ultimately shut down, even if the application is not responding to SIGTERM.

Understanding this helps in managing container lifecycles and ensuring that applications can handle shutdowns gracefully, which is critical in production environments to prevent data loss or corruption.