Docker - how i can back to docker container

List of existing instances

root ~ # docker attach 2179adde3d7f

2015/02/14 19:54:51 You cannot attach to a stopped container, start it first

root ~ # docker start 2179adde3d7f
2179adde3d7f

root ~ # docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED              STATUS              PORTS               NAMES
2179adde3d7f        ubuntu:latest       "/bin/bash"         About a minute ago   Up 2 seconds                            jolly_pare
        
root ~ # docker attach 2179adde3d7f

root@2179adde3d7f:/