Advice on camera and microphone in WSL2 Ubuntu

At the time of writing these lines, almost everything we connect to our devices is through the so-called Universal Serial Bus (USB): cameras, microphones, external storage… It’s the fastest and safest way to synchronize and backup information between our mobile phone and computer! But what does all this have to do with the Windows Subsystem for Linux (WSL2 Ubuntu)? Let’s have a look.

Study in WSL2 with Ubuntu: proprietary and free software

To begin with, I will leave you a link to an article published in this blog, in order to facilitate knowledge of the technology I will be discussing. I will add more of them throughout the text. We have quite a bit to go through, so I recommend a nice, steaming cup of black coffee in your hands before we start.

*The Last tests I have carried out have been on virtual machines (VirtualBox®: they may be created, erased, modified, etc. on Solid State Drive).

Brief retrospective

I always say that “in order to know where we are going, we need to know where we come from.” Since 1989, I have worked with the products sold by the Microsoft Corporation: first the MS-DOS operating system and its only form of command-line interaction, and then Microsoft Windows, which also uses the graphical environment. Yes, I am well aware, MS-DOS® as such was eliminated, but its commands remain. It was replaced with Powershell®, which we have already talked about, and it is important for today’s topic.

At the end of 2016, Microsoft surprised us with the news that its SQL Server® could be run on GNU/Linux. For me, who for many years worked installing and maintaining data servers for my clients, this was shocking news. But wait, there’s more, on my journey, I discovered that   BASHware can affect a Windows system via WSL. Which brings us to today’s article, where we’ll go into handling USB devices, with particular attention to microphones and webcams, under WSL2 with Ubuntu 20.04.

WSL and WSL2

I recommend, again, the excellent article on WSL2. Although time has passed and there are some significant changes. At that time, WSL2 was installed by means of commands. Now, and I want to emphasize it, I notice that by MS Windows Control Panel, “Programs and Features”, we can add the two key components that are Virtual Machine Platform and obviously Windows Subsystem for Linux in the section of “Turn Windows features on or off”:

After this, the operating system must be restarted, this is already an idiosyncrasy of the house of Redmond! (There will be many more resets later that I will leave out. They will be implied.)

Another aspect that was added in July 2021 is the possibility of adding the Linux distributions that one wishes, directly, through the command line in Powershell (depending on the version and type of MS Windows that you have installed).

To see the available distributions:

wsl --list --online

To install Ubuntu 20.04:

wsl --install -d Ubuntu-20.04

After some time, depending on your Internet download speed, it will ask for username and password. It will immediately display the status of updates for Ubuntu.

To set WSL2 as default:

wsl --set-default-version 2

The option to download and use from the Microsoft Store is still valid and available, for Ubuntu 20.04 it takes almost half a gigabyte of space.

The fundamental difference between WSL and WSL2 is that the latest download is a complete Linux kernel, but not just any kernel, it is one specially designed to be coupled with the Windows kernel. This means that applications running on WSL2 will always have to be “passed through” -but not interpreted, as it was in WSL- before interacting with any hardware, USB included.

The only thing WSL does better than WSL2 is file sharing between the two operating systems. Apart from that, WSL2 offers many more advantages and improvements in WSL2.

Podman in WSL2

To give you an idea of how useful it is to include a full Linux kernel in MS Windows, the Podman software (Docker’s successor) can be run on WSL2. If you still don’t know what Podman is, make more coffee and read another of our articles.

Developer mode

A feature that Powershell offers that you may use to your advantage, once you have installed and configured WSL2, is the developer mode. It is accessed by pressing the Windows start key, typing “Powershell” and choosing the developer settings. The first thing is to activate the developer mode and wait for the necessary software to finish installing.

This consists of two main components: 

• Device Portal.
• Device Discovery.

The Device Portal will open port 50080 (remember to properly configure the Windows Defender Firewall), and from any web browser you may enter the configured credentials and access a variety of aspects that you can see in the following image.

*There is a tutorial for establishing safe connections with HTTPS but it is irrelevant for this article:

Differences aside, this is similar to what eHorus offers for both basic and advanced monitoring, if used together with Pandora FMS. I have included this feature because the configured credentials are required for the next point.

The second component is Device discovery which, among other aspects, will open an SSH server to make a connection. 

This allows us to open a terminal with the Windows command line and, once there, you may directly use WSL2 for any task that you need to develop remotely from another computer. In this case, as an example I used the PuTTY software to connect from the real machine to the Windows 10 virtual machine with WSL2 installed and configured: 

As you can see, once the default configuration has been established, just by typing the command wsl you will be ready in a Linux environment, not GNU/Linux but MSW/Linux.

USB in WSL2

We come to the purpose of this blog post: USB handling in WSL2. At the time of writing these lines, there are two pieces of news, one bad and one good.

• The bad news is that no, WSL2 is currently unable to support USB, so for example your USB connected cameras and microphones will not be available to be used from WSL2.
• The good news is that you may compile your own Linux kernel for WSL2 and have access to the occasional microphone or webcam from your chosen Linux distribution. But what applications could you use for it?

Compiling Linux kernel for WSL2

Before doing anything, first update Ubuntu WSL2 with the usual commands:

$ sudo apt update

$ sudo apt upgrade

And if you thought that this was enough software download… well not, now what I call the programming environment (dependencies) must be installed:

$ sudo apt install build-essential flex bison libssl-dev libelf-dev

And now you may download the base kernel source code for Ubuntu on WSL2:

$ sudo git clone https://github.com/microsoft/WSL2-Linux-Kernel.git

There are three gigabytes to download. The source code. Awesome.  Although you may always use the parameter git clone -depth=1<repository>, I did not use that option. I recommend at least 100 gigabytes free in storage before going into the downloaded folder (cloned repository) and running:

$ make -d KCONFIG_CONFIG=Microsoft/config-wsl

At this point I must clarify that I found many configuration options to compile. For example, to install the software for handling Snap packages on Debian. However, all this is excluded from Microsoft support, nothing you will be able to complain to this company if something goes wrong in the compilation process.

To finish off, turn off WSL2 with the command wsl –shutdown and copy the newly compiled kernel in the following way, not without first backing up the original kernel:

C:\Windows\System32\lxss\tools\kernel

At this point you should be able to connect any microphone or webcam and have access from WSL2… But it’s going to be no. It turns out that you must first get the hardware drivers for MS Windows, obviously, and then the Linux ones, enter in the source code the latter and recompile again. In addition to that, install in Ubuntu WSL2:

sudo apt install linux-tools-5.4.0-77-generic hwdata

sudo update-alternatives --install /usr/local/bin/usbip usbip /usr/lib/linux-tools/5.4.0-77-generic/usbip 20

And by the way, it must also be installed on Windows, with an MSI installer package, the USBIPD-WIN project…

As we can see, since we have gotten used to the graphical simplicity of Windows, if you disable the USB through the Device Manager, no hardware will be able to connect with or without your consent, since it will be blocked at operating system level.

Installing graphical applications in WSL2

Finally, although in the case of the snap package installer it is explicitly unsupported in Ubuntu over WSL2, other applications that interact with hardware (such as sound, for example) will be able to be installed, but when they try to access files of hardware (remember that in Linux everything is a file) because they simply will not find such resources. This is the case of the espeak software:

In theory, the Ubuntu blog indicates that by means of X Window System Architecture it is possible to “pass” the graphical interface of the applications installed in WLS2. Microsoft officially announced just before the end of 2021 that the following graphics applications can be run:

• Gedit (my favorite graphical GNU text editor).
• GIMP (powerful for graphic design).
• Nautilus (file explorer).
• VLC (audio and video player).
• Applications based on X11 (calculator, clock, etc.).
• Google Chrome (at your own risk due to its high RAM and resource consumption).
• Microsoft Teams (by the way, Pandora FMS has a special connector).
• Even Microsoft Edge web browser for Linux!

But this has some drawbacks. First, you must have Windows 11 Build 22000. Second, have the video hardware drivers for WSL2 installed. Third, be enrolled in the Windows Insider Program. I hope you liked the information!