Exposing a tty serial device requires privileged and doesn't work

[reconbot]

Expected behavior

That I can expose a tty dev device from my mac to a linux container by running.

$ docker run --rm -it -v `pwd`:/app --device /dev/tty.usbmodem1421 node bash

Actual behavior

$ docker run --rm -it -v `pwd`:/app --device /dev/tty.usbmodem1421 node bash
docker: Error response from daemon: linux runtime spec devices: error gathering device information while adding custom device "/dev/tty.usbmodem1421": lstat /dev/tty.usbmodem1421: no such file or directory.

I can work past this with --privileged but I don't see it in /dev/

$ docker run --rm -it -v `pwd`:/app --device /dev/tty.usbmodem1421 --privileged node bash
root@5a6a7f6b8e58:/# ls /dev/tty.*
ls: cannot access /dev/tty.*: No such file or directory

According to the docs on docker run I shouldn't need --privileged.

Information

• Full output of the diagnostics from "Diagnose & Feedback" in the menu

Docker for Mac: version: 1.12.3-beta29.3 (619507e)
OS X: version 10.12.1 (build: 16B2555)
logs: /tmp/E9C6B44E-7492-484A-A6EF-EE5BE163959F/20161105-153323.tar.gz
[OK]     vmnetd
[OK]     dns
[OK]     driver.amd64-linux
[OK]     virtualization VT-X
[OK]     app
[OK]     moby
[OK]     system
[OK]     moby-syslog
[OK]     db
[OK]     env
[OK]     virtualization kern.hv_support
[OK]     slirp
[OK]     osxfs
[OK]     moby-console
[OK]     logs
[OK]     docker-cli
[OK]     menubar
[OK]     disk

• Page URL if this is a docs issue or the name of a man page
  https://docs.docker.com/engine/reference/run/#/runtime-privilege-and-linux-capabilities

Steps to reproduce the behavior

1. hook up a tty serial device such as an Arduino, usb serial dongle, modem, cash drawer, etc to your mac
2. Run the commands above to expose it's /dev/tty.usbXXXX device to the docker image
3. Look for the device

[justincormack]

Unfortunately the Mac and Linux are running in different operating systems and cannot see the same devices. I think there are some existing issues, the way to implement it will differ for different device types, but it is not trivial.

[larsks]

Take a look at boot2docker/boot2docker#707 for some discussion on this topic.

[reconbot]

That all makes sense. Should we have some sort of error instead of a silent failure?

[ijc]

As @justincormack says this is (probably) possible but is likely to be non-trivial and is not currently a priority for us. I will file a wishlist ticket for this internally. Please 👍 the top comment if you are interested in this feature.

[SiKing]

@ijc25 Just curious: if I could convince my client to throw some money at this specifically, would that bump the priority?

[ijc]

@SiKing,

If someone (or someone's client's hired contractor) was to raise a PR against https://github.com/docker/hyperkit which added the necessary underlying support for USB device passthrough (i.e. causing the USB device to appear within the VM so the Linux usb tty class driver can be run on top) or adding some sort of serial/tty passthrough functionality (I'm not sure how that would look, but it might be a plausible approach) and work with the team to get that PR into an acceptable state to be merged into hyperkit then it ought then to be possible for d4m users to fudge things themselves to enable the passthrough locally, although it clearly wouldn't be a Supported d4m feature. Maybe d4m could supply a (most likely also unsupported) way to add hyperkit command line options to enable people to do this sort of thing more easily (at their own risk, get to keep both pieces if it breaks etc).

Another plausible alternative (and likely much simpler to achieve than passthrough if it works) might be to investigate libusb and/or usb over ip between your container and a daemon on the host, it's possible that might even be possible to setup without changes to either hyperkit or d4m (AIUI the wire protocol is intended to be portable, i.e. Mac talking to Linux is supposed to work, I don't know if that is really true though).

[gw0]

One direction to achieve a workaround is with USB over IP for which a few commercial solutions exist. Nevertheless, the Docker VM that is based on Alpine Linux does not include all necessary kernel modules (vhci-hcd). I prepared a privileged Docker container to build Alpine Linux kernel modules and insert them in the kernel of the Docker VM. Does anyone know of a free and possibly open-source USB over IP solution that works on Mac and could be used with that?