I've set up a simple Kubernetes test environment based on Docker-Multinode. I've also set up a quite large Docker image based on Ubuntu, which contains several of my tools. Most of them are written in C++ and have quite a lot of dependencies to libraries installed on the system and otherwise.
My goal is to distribute legacy batch tasks between multiple nodes. I liked the easy setup of Docker-Multinode, but now I wonder if this is the right thing for me - since I have my actual legacy applications in the other Docker image.
How can I run a Bash command on Docker container B (the Ubuntu Docker container with my legacy tools) from Docker container A (the multinode worker Docker container)? Or is this not advisable at all?
To clarify, Docker container A (the worker multinode worker Docker container) and Docker container B (the legacy tools Ubuntu Docker container) run on the same host (each machine will have both of them each).
Your question is really not clear:
Kubernetes runs Docker containers; any Docker container.
Kubernetes itself runs in Docker, and in 'multi-node' the dependencies needed by Kubernetes run in Docker, but in what is called bootstrapped Docker.
Now, it's not clear in your question where Docker A runs, vs. Docker B. Furthermore, if you want to 'distribute' batch jobs, then each job should be an independent job that runs in its own container and container A should not depend on container A.
If you need the dependencies (libraries) in Docker container B to run your job, then you really only need to use the Docker container B as your base image for your job containers A. A Docker image is layered, so that even if it is big, if another container uses it as a base image, it is only loaded once overall, so it's not a problem to have five containers of type A with B as the base image, because the base image is only loaded once.
If you really need a container to communicate with another, then you should build an API to pass commands from one to the other (a RESTful API of some sort, that can communicate via HTTP calls to pass requests for a process to run on one container and return a result).