Microsoft today announced Windows Subsystem for Linux version 2---that's WSL 2. It will feature "dramatic file system performance increases" and support for Docker. To make all this possible, Windows 10 will have a Linux kernel.
No, Microsoft isn't making Windows 10 into a Linux distribution. It will still be based on the Windows kernel. But Microsoft "will be shipping a real Linux kernel with Windows that will make full system call compatibility possible." The kernel will be compiled by Microsoft based on the latest stable branch of the kernel.org source code. It will initially be based on version 4.19 of the Linux kernel.
Microsoft's Linux kernel will be tuned for WSL 2 and "optimized for size and performance to give an amazing Linux experience on Windows." The Linux kernel will be updated through Windows Update. Yes, you'll be getting Linux kernel security updates through Windows Update. The kernel's full source code will be available online on Github.
This Linux kernel is optimized for small size, improved launch times, and low memory usage. It will replace "the emulation architecture featured in the design of WSL1."
This drastic change means WSL now offers improved file system performance. It features full system call compatibility. That means you can run Docker and other Linux apps on Windows using WSL 2. However, this isn't slow like a VM---it's as fast as WSL 1 or even faster. Here's what Microsoft says about that:
File intensive operations like
git clone,
npm install,
apt update,
apt upgrade, and more will all be noticeably faster. The actual speed increase will depend on which app you're running and how it is interacting with the file system. Initial tests that we've run have WSL 2 running up to 20x faster compared to WSL 1 when unpacking a zipped tarball, and around 2-5x faster when using git clone, npm install and cmake on various projects. We're looking forwards to seeing speed comparisons from the community when we release!
The initial release of WSL 2 will arrive by the end of June 2019 in Insider builds of Windows 10. Read Microsoft's blog for more details about its Linux kernel plans.
Microsoft is launching a new Windows Terminal app that will make this next version of WSL work even better, too.