Run commands on host when Docker containers start and stop

Question

On a firewalled Docker host you must add rules to open and close ports when containers start or stop.

One way to do it is to create a Systemd unit file per container and open/close ports with ExecStartPre/ExecStopPost directives. This has the disadvantage that relies on an external service management system and cannot use restart policies from Docker itself.

Is there a way to solve this problem with only Docker provided facilities?

The most generic solution I can think of is a facility (a plugin maybe?) to execute execute arbitrary commands on specified container events. A hooks mechanism in other words. Does Docker has something like this?

Answer 1

You can use ENTRYPOINT on docker to execute script during start up, and on this shell script you put a hook on SIGTERM using trap command

ie. create shell script start.sh

#!/bin/bash

stop() {
   echo "container is being stopped"
}

trap 'stop' #

... other command ...

Next you can hook ENTRYPOINT of docker to start.sh above