Waydroid in WSL2 with sound (Weston on top of Weston approach)

waydroidwsl2.md

Waydroid in WSL2 with sound

Requirements

Recommended to install Waydroid in a brand new Ubuntu 25.04 install. Waydroid needs a custom linux kernel. Actually just needs latest kernel for WSL2 with just these changes before compiling:

CONFIG_ANDROID_BINDER_IPC=y
CONFIG_ANDROID_BINDER_DEVICES="binder,hwbinder,vndbinder"

Make sure WSL2 uses the custom kernel and modules modifying .wslconfig (or using WSL Settings)

[wsl2]
kernel=D:\\mykernel\\bzImage-6.6.87.ANDROID
kernelModules=D:\\mykernel\\modules.vhdx

Compiling the 6.6.x kernel: Step-by-step guide

Instructions for building an x86_64 WSL2 6.6.x kernel with an Ubuntu distribution using bash are as follows:

• Install the build dependencies:
  sudo apt install build-essential flex bison dwarves libssl-dev libelf-dev cpio qemu-utils

• Download de kernel (always in a /home/user/ directory)
  git clone https://github.com/microsoft/WSL2-Linux-Kernel.git --depth=1

• Change directory to kernel's directory root
  cd WSL2-Linux-Kernel

• Modify WSL2 kernel configs:
  make menuconfig KCONFIG_CONFIG=Microsoft/config-wsl

Device Drivers --> Android --> Select "Android Binder IPC Driver" -> Save

• Build the kernel using the WSL2 kernel configuration and put the modules in a modules folder under the current working directory:
  make -j$(nproc) KCONFIG_CONFIG=Microsoft/config-wsl && make INSTALL_MOD_PATH="$PWD/modules" modules_install

• Strip symbols from modules (skip this step if you are insterested in debugging kernel's memory dumps)
  find ./modules/lib/modules/$(make -s kernelrelease) -name '*.ko' -exec strip --strip-unneeded {} \;

• Then, you can use a provided script to create a VHDX containing the modules:
  sudo ./Microsoft/scripts/gen_modules_vhdx.sh "$PWD/modules" $(make -s kernelrelease) modules.vhdx

• Copy de generated kernel and modules to the desired folder
  cp arch/x86/boot/bzImage /mnt/d/mykernel/bzImage-6.6.87.2.ANDROID
cp modules.vhdx /mnt/d/mykernel/modules.ANDROID.vhdx

• Open WSL Settings -> Developer -> Select Custom kernel, Custom modules

• Shutdown WSL2 VM
  wsl.exe --shutdown

Setup

Download ubuntu-25.04-wsl-amd64.wsl distro from https://releases.ubuntu.com/plucky/

Double click on the .wsl file to install.

Run Ubuntu 25.04 and make sure is updated

sudo apt update && sudo apt upgrade -y

Install weston

sudo apt install weston

Install Waydroid

curl -s https://repo.waydro.id | sudo bash
sudo apt install waydroid

Configure Waydroid to only use software rendering (SwiftShader)

sudo nano /var/lib/waydroid/waydroid_base.prop

    ro.hardware.gralloc=default
    ro.hardware.egl=swiftshader

Make weston detect gpu for some acceleration

export GALLIUM_DRIVER=d3d12

Run weston

weston --backend=wayland-backend.so 

Inside weston desktop shell open a terminal and run

waydroid session start

When it shows 'Android with user 0 is ready' then open another terminal inside the weston desktop and run

waydroid show-full-ui

Tips:

• If Waydroid shows some weird dbus errors make sure you shutdown the WSL2 VM (wsl.exe --shutdown) and try again.

• By default Waydroid only launches correctly if the WSL2 networking mode is not MIRRORED. This is because dnsmasq tries to reserve port 53 that is already used in Windows. If you want to keep using MIRRORED networking you will need to add this to your .wslconfig (or using WSL Settings)

  [experimental]
  ignoredPorts=53
  

• Every time the WSL2 kernel changes significantly (from ASHMEM support in 5.15.x to none in 6.6.x) you need to reconfigure Waydroid or it wont boot.

    sudo waydroid upgrade --offline
  

@onomatopellan

... I just know the official WSL2 release includes a 15Mb kernel file and a 190Mb modules.vhd file.

That's exactly why the new/custom size of "modules.vhd" (2.13GB) feels very excessive. It's over 10 times bigger.

In addition, the standard WSL2 contains "system.vhd" (388 MB) which is a separate distro where WSLg runs. Isn't that where all GPU drivers and such are expected to live ? At least, that would be a good explanation for the 388MB size.

@pilafov I asked Copilot and it recommended to strip the debug symbols of the modules. Now the modules.vhdx size is 192Mb. I updated the guide with the line find ./modules/lib/modules/$(make -s kernelrelease) -name '*.ko' -exec strip --strip-unneeded {} \;

The system.vhd is the system distro (Common Base Linux Mariner) that indeed contains WSLg. You can access to that system distro with wsl.exe -d Ubuntu-25.04 --system. There is no kernel or modules, just the files it needs for running Pulseaudio, wayland and mesa.

@onomatopellan
This is great news, thanks!
I can't wait to try it out myself but I'm out of luck as I already removed the whole kernel source tree.
I'll have to start from the beginning.
I'm sure this will greatly improve WSL2 startup time.

What about Waydroid startup ?
Did you notice any difference ?