This should probably be a comment on another answer, but I don't have the rep yet:
Running on Centos7 & Docker 1.8.2, I was unable to use Zgr3doo's solution to umount by devicemapper ( I think the response I got was that the volume wasn't mounted/found. )
I think I also had a similar thing happen with sk8terboi87 ツ 's answer: I believe the message was that the volumes couldn't be unmounted, and it listed the specific volumes that it tried to umount in order to delete the dead containers.
What did work for me was stopping docker first, and then deleting the directories manually. I was able to determine which ones they were by the error output of previous command to delete all the dead containers.
Apologies for the vague descriptions above. I found this SO question days after I handled the dead containers. .. However, I noticed a similar pattern today:
$ sudo docker stop fervent_fermi; sudo docker rm fervent_fermi fervent_fermi
Error response from daemon: Cannot destroy container fervent_fermi: Driver devicemapper failed to remove root filesystem a11bae452da3dd776354aae311da5be5ff70ac9ebf33d33b66a24c62c3ec7f35: Device is Busy
Error: failed to remove containers: [fervent_fermi]
$ sudo systemctl docker stop
$ sudo rm -rf /var/lib/docker/devicemapper/mnt/a11bae452da3dd776354aae311da5be5ff70ac9ebf33d33b66a24c62c3ec7f35
$
I did notice, when using this approach that docker re-created the images with different names:
a11bae452da3 trend_av_docker "bash" 2 weeks ago Dead compassionate_ardinghelli
This may have been due to the container being issued with restart=always, however, the container ID matches the ID of the container that previously used the volume that I force-deleted. There were no difficulties deleting this new container:
$ sudo docker rm -v compassionate_ardinghelli
compassionate_ardinghelli