README.md

Working with ephemeral (dynamically created) USB devices in Docker

In case you need to run some Android flashing utils like heimdall in Docker you need to run your container with following options of your choice.

There are two of implementation ways of this:

1. Create cgroup rule and sync devices in container by udev trigger (as described below and what I've made)
2. Run docker container with --priviliged -v /dev/bus/usb (not safe)

This repository contains an implementation of moby/moby#22563 PR:

Dealing with dynamically created devices (--device-cgroup-rule) Devices available to a container are assigned at creation time. The assigned devices will both be added to the cgroup.allow file and created into the container once it is run. This poses a problem when a new device needs to be added to a running container. One of the solution is to add a more permissive rule to a container allowing it access to a wider range of devices. For example, supposing our container needs access to a character device with major 42 and any number of minor number (added as new devices appear), the following rule would be added: docker create --device-cgroup-rule='c 42:* rmw' -name my-container my-image Then, a user could ask udev to execute a script that would docker exec my-container mknod newDevX c 42 the required device when it is added. NOTE: initially present devices still need to be explicitely added to the create/run command

1. Add sync script:

cp docker-usb-sync.py /usr/bin/docker_device_sync.py

Don't forget to change container name in script.

2. Create new udev rule:

ACTION=="add", SUBSYSTEM=="usb", RUN+="/usr/bin/docker_device_sync.py"
sudo service udev restart

3. Run container:

docker run --rm -d --device=/dev/bus/usb --device-cgroup-rule='c 189:* rmw' <image_name>

4. Device reboot:

adb reboot download
heimdall close-pc-screen

Now at every host device reconnect, a device also will be mapped into a container by our script triggered by udev.