Microsoft's WSL: A Decade-Long Odyssey to Embrace Open Source
A surprising shift in the tech world! At the Ubuntu 25.10 Summit, Microsoft's Craig Loewen and Clint Rutkas revealed the untold story of how the Windows Subsystem for Linux (WSL) finally embraced open-source principles. But this journey was far from straightforward.
It all began with Project Astoria in 2010, an ambitious attempt to run Android apps on Windows Phone. However, this project never saw the light of day. The key innovation here was translating Linux system calls into Windows NT kernel calls, which laid the foundation for WSL's future.
The first step towards WSL: In 2016, Microsoft launched Bash and Ubuntu on Windows, thanks to the initial prototype's success. This version recompiled Cygwin's open-source utilities to run natively on Windows, as explained by Dustin Kirkland from Canonical's Ubuntu team.
WSL 1.0: A Compatibility Layer: The first iteration, WSL 1.0, was a compatibility layer that enabled Linux distributions to run on Windows. It translated Linux system calls into Windows NT calls using 'pico processes.' Despite its release in 2017, users reported performance issues.
WSL 2.0: A New Direction: Microsoft listened and took a different approach with WSL 2.0, developing their own Linux kernel. This version used a lightweight VM to run the Microsoft Linux kernel, updated via Windows Update. And this is where it gets controversial—WSL 2.0 became a hit among developers, especially after its stable release in 2020.
The Open Source Push: Internally, the WSL team advocated for open-sourcing WSL 2.0, emphasizing the importance of community involvement and business value. Loewen highlighted the natural fit, given Linux's open-source nature. But it wasn't easy; they had to decouple WSL from the Windows kernel, a lengthy process.
Challenges and Triumphs: Rutkas admitted that open-sourcing requires effort and stakeholder buy-in. However, the success was immediate. The project gained thousands of stars on GitHub within a day and topped Hacker News. This proved that open-source models can drive innovation and productivity, even within Microsoft.
A New Microsoft: The WSL team's success has set a precedent for other Microsoft projects, like Windows Terminal and PowerToys. By embracing open-source principles, Microsoft has not only empowered external developers but also challenged traditional notions of proprietary technology. And this is the part most people miss—the impact of this shift on the tech industry's future.
What do you think? Is Microsoft's open-source transformation a welcome change, or does it raise concerns? Share your thoughts and let's spark a conversation!
