Cannot kill pid 1 inside docker container with SIGKILL

Question

For a reason, I want to kill the main python process ( PID 1 ) in docker container. But non of the terminating signals such as SIGTERM, SIGKILL work. I mean, running kill -SIGKILL 1 has no effect. How can I kill the pid 1 from the inside of container? I do not want to run docker stop or similar solutions.

Answer 1

According to the Docker issue tracker and how the general documentation of pid 1s state, you need to specifically add a handler to the signals and kill the process from them.

signal.signal(signal.SIGINT, exit_gracefully)
signal.signal(signal.SIGTERM, exit_gracefully)

exit_gracefully needs to be defined and eventually call sys.exit(0).

This behaviour is wanted and enforced by the kernel as it will not call the sigaction default, which is is termination, on the other pids.

We need to do something similar in Node.js.