WSL2-Linux-Kernel README

The project's README from github.com/microsoft/WSL2-Linux-Kernel. As one markdown file: README.md.

Introduction

The WSL2-Linux-Kernel repo contains the kernel source code and configuration files for the WSL2 kernel.

Reporting Bugs

If you discover an issue relating to WSL or the WSL2 kernel, please report it on the WSL GitHub project. It is not possible to report issues on the WSL2-Linux-Kernel project.

If you're able to determine that the bug is present in the upstream Linux kernel, you may want to work directly with the upstream developers. Please note that there are separate processes for reporting a normal bug and a security bug.

Feature Requests

Is there a missing feature that you'd like to see? Please request it on the WSL GitHub project.

If you're able and interested in contributing kernel code for your feature request, we encourage you to submit the change upstream.

Build Instructions

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

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

  2. Modify WSL2 kernel configs (optional):
    make menuconfig KCONFIG_CONFIG=Microsoft/config-wsl

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

    You may wish to include -j$(nproc) on the first make command to build in parallel.

  4. Install the kernel's UAPI headers into a headers folder:
    make headers_install INSTALL_HDR_PATH="$PWD/headers"

  5. Build the perf tooling into a perf folder:
    make -C tools/perf NO_JEVENTS=1 NO_JVMTI=1 NO_LIBTRACEEVENT=1 install DESTDIR="$PWD/perf" prefix=/

Then, you can use a provided script to create a VHDX containing the modules, headers, and perf tooling: ./Microsoft/scripts/gen_artifacts_vhdx.sh "$PWD/modules" "$PWD/headers" "$PWD/perf" $(make -s kernelrelease) modules.vhdx

To save space, you can now delete the compilation artifacts: make clean && rm -r "$PWD/modules" "$PWD/headers" "$PWD/perf"

If you prefer, you can also build the VHDX manually as follows. WSL expects the artifacts laid out under <kernelrelease>/{modules,linux-headers,perf}, so first assemble a staging directory:

  1. Stage the modules, headers, and perf tooling under the kernel release directory:

    release=$(make -s kernelrelease)
mkdir -p "$PWD/staging/$release/linux-headers"
cp -r "$PWD/modules/lib/modules/$release" "$PWD/staging/$release/modules"
rm -f "$PWD/staging/$release/modules/build" "$PWD/staging/$release/modules/source"
cp -r "$PWD/headers/." "$PWD/staging/$release/linux-headers"
cp -r "$PWD/perf" "$PWD/staging/$release/perf"

  2. Calculate the image size (plus 256MiB for slack): image_size=$(du -bs "$PWD/staging" | awk '{print $1;}'); image_size=$((image_size + (256 * (1<<20))));

  3. Build a populated ext4 image: mke2fs -L '' -d "$PWD/staging" -N $(( $(find "$PWD/staging" | wc -l) + 4096 )) -b 1024 -t ext4 "$PWD/modules.img" $((image_size / 1024))

  4. Convert the img to VHDX: qemu-img convert -O vhdx "$PWD/modules.img" "$PWD/modules.vhdx"

  5. Clean up: rm "$PWD/modules.img" # optionally the $PWD/staging, $PWD/modules, $PWD/headers, and $PWD/perf dirs too

Install Instructions

Please see the documentation on the .wslconfig configuration file for information on using a custom built kernel.

WSL2-Linux-Kernel (microsoft/WSL2-Linux-Kernel)

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10.6K ·GitHub
WSL2-Linux-Kernel
What is this?This is the official source repository for the Linux kernel that powers WSL2 (Windows Subsystem for Linux 2), including the kernel source code and configuration files used by Microsoft.
Is this a ready-to-use app or just kernel source code?It's raw kernel source code and build configuration, not an installable application. You compile it yourself if you need a custom WSL2 kernel instead of the one Microsoft ships by default.
How do I build a custom WSL2 kernel from this?Install build dependencies, run 'make menuconfig KCONFIGCONFIG=Microsoft/config-wsl' to tweak config, then 'make KCONFIGCONFIG=Microsoft/config-wsl' to build and install modules, followed by building headers and perf tooling, and packaging everything into a VHDX with the provided script.
What do I need installed before building it?You need a Linux build environment (e.g. Ubuntu) with build-essential, flex, bison, dwarves, libssl-dev, libelf-dev, cpio, qemu-utils, and rsync.
Who actually needs to build this themselves?Mainly advanced WSL users or kernel developers who want custom kernel modules, drivers, or config options not included in Microsoft's default shipped kernel.
Where does the resulting kernel get used?The built kernel/VHDX is loaded by WSL2 on Windows via the .wslconfig file, replacing the default kernel for your Linux distros running under WSL2.
How do I actually use a kernel I built myself?Point WSL to it using the custom kernel setting in the .wslconfig configuration file, as documented in the Install Instructions section.
Should I submit kernel feature changes to this repo?If your feature is relevant to upstream Linux, you're encouraged to submit the patch upstream directly rather than only changing this repo's fork.
What target architecture do the build instructions cover?The documented build steps are specifically for building an x86_64 WSL2 kernel on an Ubuntu-based bash environment.
What are similar projects?lowlevelprogramming-university, linux, openwrt, mu300-linux, linux, open-gpu-kernel-modules, lua, lytlnyblOS
Which topics is it in?build-system, linux-kernel, wsl, embedded-systems, kernel, virtualization, low-level, microsoft, compiler, hardware, sysadmin, c
Creator
microsoft
Size
2.9 GB
Stars
10.6K
Updated
CommitOct 06Releaselinux-msft-wsl-6.18.54.1Oct 06
Age
7y
Commits · 90 Days