"dead" probably appearing with overlay2

[robnagler]

I'm seeing moby/moby#34463 with overlay2 on CentOS 7:

dockerd[4684]: time="2017-12-10T17:26:37.589403566Z" level=error msg="Error removing mounted layer cef739c6607bdd3f739a355e1fbaf91cf199a5bd52333243a121c27ab68ab86d: remove /var/lib/docker/overlay2/2e5887ca38faa4ec3ecb3e380cac27c9520f67cbb920c43df3682e7e31c864fe/merged: device or resource busy"

[robnagler]

Another workaround is in moby/moby#34886, which isn't available yet so the fix is:

sysctl -w fs.may_detach_mounts = 1

The deeper issue seems to be a race condition in Docker. I haven't seen anybody working on a fix to this. Hopefully this is the "last" workaround.

Also passing docker run --init, which calls /bin/init, which hopefully works around any zombie issues that might be causing device busy.