These three commands are used to change the state of a container from running to stopped or restart it.
Stop: When a user issues this command, the Docker engine sends SIGTERM (-15) to the main process, which is running inside the container.
The SIGTERM signal requests the process to terminate itself gracefully. Most of the processes would handle this signal and facilitate a graceful exit. However, if this process fails to do so, then the Docker engine will wait for a grace period. Even after the grace period, if the process has not been terminated, then the Docker engine will forcefully terminate the process. The forceful termination is achieved by sending SIGKILL (-9).
The SIGKILL signal cannot be caught or ignored, and so it will result in an abrupt termination of the process without a proper clean-up.
$ docker stop | start| restart [OPTIONS] CONTAINER [CONTAINER...]
[Options] -t, --time=10 Seconds to wait for stop before killing it [Container] Control the container either by Name or ID
$ sudo docker start Your_Ubuntu_Container