As mentioned before, Axle containers are for hosting regular or bind-mounted volumes. This can be host-specific persistent data, or any other type of volume container.
By default, Radial uses such a container to store the Supervisor log output of each spoke container. Rather then make a decision on which log management one should use, they are instead simply collated into a single location. It's the job of some other spoke container to harvest/serve/analyze these logs later if one so chooses.
Let's create our above example and make a "logs" Axle container. If we choose to make a permanent image that we can reuse, the Dockerfile would possibly contain:
FROM radial/axle-base
VOLUME ["/log"]
CMD ["IDLE"]
Note that the program "IDLE" is the equivalent of tail -f /dev/null meant
solely to keep the container from exiting. This makes container management a bit
more intuitive regarding volume containers.
It could be built via:
docker build -t logs .
and run via:
docker run --name logs logs
Building this container however doesn't have any benefits, so usually it can just be run directly from command line with:
docker run --name logs --volume /log radial/axle-base IDLE