WSL2: Ubuntu 18.04 Serial devices are no longer mounted properly

[david-dumke]

• Your Windows build number: Microsoft Windows [Version 10.0.18932.1000]

• What you're doing and what's happening:

1. run WSL2 Ubuntu 18.04
2. plugin USB to serial device
3. watch it mount under COM devices in device manager
4. attempt to open the device in WSL2
5. cat /dev/ttyS[X]

• What's wrong / what should be happening instead:
  This works under WSL1 flawlessy, it no longer works in WSL2
  in WSL2 we can clearly see it is not connected or configured
  /dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
  

[rubberduck203]

It’s clearly called out in the FAQ that there is currently no support for USB in WSL2.

I’d like to toss my voice in here that this should be a priority feature for WSL2.

One of the big benefits of WSL2 is the opportunity to run Docker natively instead of on Docker for Windows. It is notoriously hard to get access to USB devices in Docker on non-Linux systems.

I commonly use Docker for creating tool-chain images, but this falls apart when you’re working with embedded devices, where you need to connect to a USB device or serial port in order to flash/debug on device. If I can run a docker container natively and access USB ports with WSL2, I can make an extremely strong argument for switching from Mac to Windows.

[linweifu]

up

[zawawimanja]

so that why I cannot see my usb device in ubuntu.hurmmm

[rubberduck203]

It would be really nice if someone could chime in letting us know if this is even technically feasible.

[sebbean]

would love to know

[chenhu66]

what a pity! i gotta roll back to wsl 1. Hopefully, usb support comes up soom for wsl2

[tleroy-dev]

what a pity! i gotta roll back to wsl 1. Hopefully, usb support comes up soom for wsl2

Can I have the detailed step to roll back from WSL2 to WSL1 ?
I found under https://docs.microsoft.com/en-us/windows/wsl/release-notes#build-18917 that WSL2 was introduced at build version 18917. Now, how can I re-install WSL from a specific build number ? Thank you.

EDIT my current build number is below 18917 and should be WSL1, right ? But the USB COM PORT is not recognized in WSL env.

My current os version:

PS C:\Users\nxf43719> [System.Environment]::OSVersion.Version

Major  Minor  Build  Revision
-----  -----  -----  --------
10     0      17134  0

[rubberduck203]

I thought you could have WSL1 and WSL2 installed side by side?

[tleroy-dev]

@rubberduck203 it's not clear to me how to check which WSL version we are running. It is not described in the app store. From online information I have found:

We need to run Windows Build 16215 or later to install WSL 1.

WSL 2 is only available in Windows Builds 18917 or higher.

You can install both version if your build is higher than 18917.
So in my case I am running a 17134 build, I should only have WSL1 available, correct ?
In my case I still have troubles accessing serial USB device from my linux terminal under /dev/. They don't show up but are dettected in Windows Device Manager.

[bburky]

@tleroy-dev If your system supports WSL2, you can choose WSL1 or WSL2 per distro.

VERSION from wsl --list --verbose shows if you're using WSL1 or WSL 2:

> wsl --list --verbose
  NAME                   STATE           VERSION
* docker-desktop-data    Stopped         2
  docker-desktop         Stopped         2
  Ubuntu-18.04           Stopped         2
  Fedora-32              Stopped         2
  Ubuntu                 Stopped         1

The normal recommendation is to use WSL2 for installation of all new WSL distros. Note, this doesn't affect your current installed WSL distros, if you have any already they will stay on WSL1.

wsl --set-default-version 2

If you want to manually upgrade a distro to WSL2 or "downgrade" it to WSL1, you can use --set-version. I keep a WSL1 distro around to have functioning /dev/ttyS* devices.

wsl --set-version Ubuntu 1

[tleroy-dev]

@bburky Thanks for your response.

PS C:\Users\user> wsl --list --verbose
/bin/bash: --: invalid option

From that documentation, it looks like the wsl.exe command works only on build higher than 1903, older version use wslconfig.exe. Result of equivalent :

PS C:\Users\user> wslconfig.exe /list /all
Distributions du sous-système Windows pour Linux :
Ubuntu (par défaut)

It's in french in my case (system default), it does not output the version specifically, I guess from what I have described earlier, being on a pre-WSL2 build (17134) , only WSL 1 is enabled in my case.