Microsoft Build 2019: Introducing WSL 2, the newest architecture for the Windows Subsystem for Linux

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Yesterday, on the first day of Microsoft Build 2019, the team at Microsoft introduced WSL 2, the newest architecture for the Windows Subsystem for Linux. With WSL 2, file system performance will increase and users will be able to run more Linux apps. The initial builds of WSL 2 will be available by the end of June, this year.

What’s new in WSL 2?

Run Linux libraries

WSL 2 powers Windows Subsystem for Linux to run ELF64 Linux binaries on Windows. This new architecture brings changes to how these Linux binaries interact with Windows and computer’s hardware, but it will still manage to provide the same user experience as in WSL

Linux distros

With this release, the individual Linux distros can be run either as a WSL 1 distro, or as a WSL 2 distro, and can be upgraded or downgraded at any time. Also, users can run WSL 1 and WSL 2 distros side by side. This new architecture uses an entirely new architecture that uses a real Linux kernel.

Increases speed

With this release, file-intensive operations like git clone, npm install, apt update, apt upgrade, and more will get faster. The initial tests that the team has run have WSL 2 running up to 20x faster as compared to WSL 1, when unpacking a zipped tarball. And it is around 2-5x faster while using git clone, npm install and cmake on various projects.

Linux kernel with Windows

The team will be shipping an open source real Linux kernel with Windows which will make full system call compatibility possible. This will also be the first time a Linux kernel is shipped with Windows. The team is building the kernel in house and in the initial builds they will ship version 4.19 of the kernel.

This kernel is been designed in tune with WSL 2 and it has been optimized for size and performance. The team will service this Linux kernel through Windows updates, users will get the latest security fixes and kernel improvements without needing to manage it themselves. The configuration for this kernel will be available on GitHub once WSL 2 will release. The WSL kernel source will consist of links to a set of patches in addition to the long-term stable source.

Full system call compatibility

The Linux binaries use system calls for performing functions such as accessing files, requesting memory, creating processes, and more. In WSL 1 the team has created a translation layer that interprets most of these system calls and allow them to work on the Windows NT kernel. It is challenging to implement all of these system calls, where some of the apps don’t run properly in WSL 1. WSL 2 includes its own Linux kernel which has full system call compatibility.

To know more about this news, check out Microsoft’s blog post.

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