shell - Docker Copying file from host to container

Question

I am trying to copy a set of files from docker host to container. On a AUFS system directly going into /var/lib/docker/aufs/... works. However I am another system with Fedora that has devicemapper as the storage driver. On this system if I do this:

[root@myhost tmp]# docker inspect -f '{{.Id}}' 393ef4b9f485
393ef4b9f485dafc78037f59bdbeda16d63b8338487248ed25b68cf544f29e24
[root@myhost tmp]# cd /var/lib/docker/devicemapper/mnt/393ef4b9f485dafc78037f59bdbeda16d63b8338487248ed25b68cf544f29e24
[root@myhost 393ef4b9f485dafc78037f59bdbeda16d63b8338487248ed25b68cf544f29e24]# ls -l
total 0
[root@myhost 393ef4b9f485dafc78037f59bdbeda16d63b8338487248ed25b68cf544f29e24]#

I get nothing. I have tried all suggestions from Copying files from host to Docker container

Using tar seems to be great, instead of directly going to the underlying FS. But I cannot assume that tar would be present in all containers.

If it is relevant, I have even tried to create a file in the container, but it and then did a find . -name in /var/lib/docker/devicemapper/mnt to no avail.

Any hints?

EDIT 1: Based on one of the answers, adding these constraints. The intent is to copy files into a container without a. not modify the containers build (Dockerfile), b. To not install any ssh or ftp daemons. and c. not even change the way the container was started.

EDIT 2: Adding the docker info :

# docker info
Containers: 1
Images: 21
Storage Driver: devicemapper
 Pool Name: docker-253:0-397467-pool
 Pool Blocksize: 65.54 kB
 Backing Filesystem: extfs
 Data file:
 Metadata file:
 Data Space Used: 4.261 GB
 Data Space Total: 107.4 GB
 Data Space Available: 103.1 GB
 Metadata Space Used: 3.596 MB
 Metadata Space Total: 2.147 GB
 Metadata Space Available: 2.144 GB
 Udev Sync Supported: true
 Library Version: 1.02.90 (2014-09-01)
Execution Driver: native-0.2
Kernel Version: 3.17.4-301.fc21.x86_64
Operating System: Fedora 21 (Twenty One)
CPUs: 4
Total Memory: 3.86 GiB
Name: fedora-docker

Docker Version is 1.6.0 and container image is based on RHEL.

Answer 1

UPDATE: Now docker cp command line command works both ways. See the docker cp documentation

Usage

docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH|-

docker cp [OPTIONS] SRC_PATH|- CONTAINER:DEST_PATH

=======Original Answer ==============

Found the most easiest way that works across storage drivers:

cd /proc/`docker inspect --format "{{.State.Pid}}" <containerid>`/root

Have tested this on Fedora with Devicemapper as the storage driver and on Ubuntu with AUFS as the storage driver. Works for me in both the cases.