root@testhost:~# uname -a
Linux testhost 3.18.5-031805-generic #201501292218 SMP Fri Jan 30 03:19:17 UTC 2015 x86_64 GNU/Linux

root@testhost:~# docker info
Containers: 1
 Running: 0
 Paused: 0
 Stopped: 1
Images: 9
Server Version: 1.10.0-dev
Storage Driver: overlay
 Backing Filesystem: extfs
Execution Driver: native-0.2
Logging Driver: json-file
Plugins:
 Volume: local
 Network: host bridge null
Kernel Version: 3.18.5-031805-generic
Operating System: Debian GNU/Linux 8 (jessie)
OSType: linux
Architecture: x86_64
CPUs: 8
Total Memory: 1.899 GiB
Name: loxflix
ID: RNAT:QYNF:66KE:DSN5:NRPC:ITAA:6G3M:WMR2:JABB:CPGO:ZN7O:FAVU
Debug mode (server): true
 File Descriptors: 13
 Goroutines: 31
 System Time: 2016-01-24T08:45:00.139001319Z
 EventsListeners: 0
 Init SHA1: b84242d186971c8111d1f9de77b7c476bc049614
 Init Path: /usr/lib/docker/dockerinit
 Docker Root Dir: /var/lib/docker
Labels:
 provider=generic
Experimental: true

root@testhost:~# findmnt -o TARGET,PROPAGATION /mnt/testhost
TARGET       PROPAGATION
/mnt/shared shared

root@testhost:~# docker run --rm -it --volume /mnt/shared:/data:shared ubuntu:14.04
docker: Error response from daemon: Cannot start container 6859ea4fc2f23130da7e72f301c9a82528c6e78e406b6f68261d000410ad6960: Path /mnt/shared is mounted on /mnt/shared but it is not a shared mount..