You're reading the documentation for a version of ROS 2 that has reached its EOL (end-of-life), and is no longer officially supported. If you want up-to-date information, please have a look at Foxy.

Running 2 nodes in a single docker container [community-contributed]

Pull the ROS docker image with tag “dashing-desktop”.

docker pull osrf/ros:dashing-desktop

Run the image in a container in interactive mode.

$ docker run -it osrf/ros:dashing-desktop
root@<container-id>:/#

Your best friend is the ros2 command line help now.

root@<container-id>:/# ros2 --help

E.g. list all installed packages.

root@<container-id>:/# ros2 pkg list
(you will see a list of packages)

E.g. list all executables:

root@<container-id>:/# ros2 pkg executables
(you will see a list of <package> <executable>)

Run a minimal example of 2 C++ nodes (1 topic subscriber listener, 1 topic publisher talker) from the package demo_nodes_cpp in this container:

ros2 run demo_nodes_cpp listener &
ros2 run demo_nodes_cpp talker