title: Docker on the mac separates internal and external file ownerships; not so on linux
body: <p>Running docker on the Mac, with a centos image, I see mounted volumes taking on the ownership of the centos (internal) user, while on the filesystem the ownership is mine (mdf:mdf).</p>
  
  <p>Using the same centos image on RHEL 7, I see the volumes mounted, but inside, in centos, the home dir and the files all show my uid (1055).</p>
  
  <p>I can do a recursive chown to, e.g., insideguy:insideguy, and all looks right. But back in the host filesystem, the ownerships have changed to some other person in the registry that has the same uid as was selected for insideguy(1001) when useradd was executed.</p>
  
  <p>Is there some fundamental limitation in docker for Linux that makes this happen?</p>
  
  <p>As another side effect, in our cluster one cannot chown on a mounted filesystem, even with sudo privileges; only on a local filesystem. So the desire to keep the docker home directories in, e.g., ~/dockerhome, fails because docker seems to be trying (and failing) to perform some chowns (not described in the Dockerfile or the start script, so assumed to be part of the --volume treatment). Placed in /var or /opt with appropriate ownerships, all goes well.</p>
  
  <p>Any idea what's different between the two docker hosts?</p>
  
  <p>Specifics: OSX 10.11.6; docker v1.12.1 on mac, v1.12.2 on RHEL 7; centos 7</p>