Working with Docker containers

This is a docker cookbook of sorts.

Launching a GUI application with docker

My final object is to run the gnuradio-companion GUI through a docker container.

Why bother?
Because GNURadio loves to muck up the entire system regardless of the OS used. It also doesn’t like to live in non-standard directories (most tools then fail to run) which leaves out the option os a parallel install. So containerization is probably the right option :-/

Running GUI apps with Docker - Somatorio (Nov 2018)

Docker Containers on the Desktop - Jess Frazelle (Nov 2018)

Here was my timeline

1. Check if there is a gnuradio docker image available.
   I checked available images with docker search gnuradio and found marcelmaatkamp/gnuradio to be a promising option 1.

What finally worked

docker run -e DISPLAY=host.docker.internal:0 --entrypoint gnuradio-companion -it marcelmaatkamp/gnuradio

Notes:

• The -t flag is not necessarily required but gives GNURadio debugging outputs

Check which docker images are installed

docker images

Find the ID or names of currently running containers

docker ps

docker -s -qa will provide the names of containers without additional info. Useful to combine with other docker commands like docker stop and docker rm

Stop containers

docker stop <container name or ID>

Convenient way to stop all running containers docker stop $(docker ps -qa)

Remove containers

Note: only stopped containers can be removed.

docker rm <container name or ID>

Convenient way to remove all stopped container docker rm $(docker ps -qa)

Remove the downloaded docker image

Note: Images can only be removed if there are no running or stopped containers using this image

docker rmi <image name>

Trying to launch a simple GUI image called gns3/xeyes

Before we can run a docker GUI, we need to add localhost to allowable connection list for the X window server.

xhost + 127.0.0.1 Or
xhost + localhost

Then run the docker container (using the default script) docker run -e DISPLAY=host.docker.internal:0 gns3/xeyes

What is happening here? host.docker.internal:0 is the IP address of the computer (and port) where the X server is running

How to explore the contents of a docker container? docker run –rm -it –entrypoint=/bin/bash name-of-image

The rm flag automatically removes the container after it exits

Taking a snapshot of a container

# find ID of your running container:
docker ps -a

# create image (snapshot) from container filesystem
    docker commit 12345678904b5 mysnapshot

# explore this filesystem using bash (for example)
    docker run -t -i mysnapshot /bin/bash

# remove snapshot after we’re done
    docker rmi mysnapshot

docker exec

Note: exec is used to run another command in an already running container.

docker exec -it <running container name or ID> bash

Docker exec - CLI Reference (Nov 2018)