title: How to solve /dev/mapper/docker full?
body: <p>I'm working on some docker container. 
  While trying to install some python packages /dev/mapper/docker gets filled.
  I read <a href="https://stackoverflow.com/questions/37672018/clean-docker-environment-devicemapper/37681340">Clean docker environment: devicemapper</a>, but this would stop ruining containers and impact the current workflow. How can I reduce it's size without effecting running containers ?</p>