rename

 docker rename docker_ubuntu docker_ubuntu_new_name

[root@dotohi ~]# docker rename docker_ubuntu docker_ubuntu_new_name
[root@dotohi ~]# docker ps
CONTAINER ID   IMAGE     COMMAND   CREATED         STATUS         PORTS     NAMES
264c3039999c   ubuntu    "bash"    7 minutes ago   Up 7 minutes             docker_ubuntu_new_name