title: Increase /dev/shm in docker container in swarm environment (docker stack deploy)
body: <p>I know is possible to increase default 64MB /dev/shm in docker container from docker run or docker compose. As example this works in our local development machines.</p>
  
  <pre><code>version: '3.5'
  services:
    postgres:
      image: postgres
      shm_size: '1gb'
  </code></pre>
  
  <p>However when I try to do it in our swarm docker stack deploy stack_name -c docker-compose.yml I get a "Ignoring unsupported options: shm_size" and shm mount remains as default 64MB. </p>
  
  <p>What can I do? I tried to create an image with this parameter but it seems is not something that I can add to image built, more like a runtime option. It's possible to modify it after container creation?</p>
  
  <p>Environment is an Ubuntu 16.04 with docker 17.12 in a single node swarm.</p>