title: Can't resolve set hostname from another docker container in same network
body: <p>I've had db and server container, both running in the same network. Can ping db host by its container id with no problem.
  When I set a hostname for db container manually (<code>-h myname</code>), it had an effect (<code>$ hostname</code> returns set host), but I can't ping that hostname from another container in the same network. Container id still pingable.
  Although it works with no problem in docker compose.
  What am I missing?</p>