Using USB with Docker for Mac

If you’ve been struggling with this issue and just want an answer, skip to the bottom for the TL;DR. I won’t fault you for it.

---

Docker is a great tool for deploying web services, but one of my favorite uses for it is standardizing toolchains. Instead of everyone on the team needing to setup their development environments identically, and them keeping them in sync, you define the build tools in a single place, a docker image. Then everyone, including your build server, uses that single pre-packaged image.

Not only is this great for teams, but it’s also fantastic when you have side projects that you only periodically revisit. Without fail, when I come back to some old project, I’ve seen updated my tools for something newer, and I can’t build that old project without either upgrading the project or degrading my tools. Leaving a build tools image behind means I can just pick it up and work on it without spending a day getting back up and running.

It’s not all sunshine and roses though. I went on quite an adventure today. Last year I put on a TDD for Arduino workshop. I had started to create a Docker image for AVR development,  but ran into problems when it came time to flash the program to the board. Exposing a USB port to a docker container on Mac isn’t exactly a trivial task (until you know how at least!). For that session we mobbed, so I only had to setup one machine. I just stopped fighting with it and went with a regular install of the tools on my machine.

Recently though, I’ve taken a renewed interest in getting this to work properly. First, I’ve been playing with ARM development, but there’s a bug in AVR and ARM’s compiler packaging that means you can’t have both toolchains installed at the same time. Having these toolchains containerized means I can easily keep both readily available. Secondly, I’m now beginning to build on that workshop to turn it into an “Intro to Bare Metal Programming” course. For that, I really need to be able to hand folks an environment I know works, so we’re not spending more time working kinks out of dev setups than learning. Also, in order to standardize embedded toolchains for a team or client at work, I really need to know how to get USB working on Mac.