I am using as a base the php docker container with the tag:
php:5.6-apache
When I try to restart the apache2 inside the container, the containe
sudo docker kill --signal="USR1" your_appache_container
Other signals that you can use to achieve the following :
Stop Now Signal: TERM
Graceful Restart Signal: USR1
Restart Now Signal: HUP
Graceful Stop Signal: WINCH
From: this website