BEFORE — WSL1 faked Linux

In 2020, Microsoft started shipping genuine Linux kernel inside Windows, delivered through Windows Update. WSL2 runs the real kernel.org kernel in a lightweight Hyper-V utility VM that boots in about a second, so essentially every Linux program runs unmodified. The story started in 2016 when Microsoft launched the first Windows subsystem for Linux, WSL. Developers had been asking for years for real Linux tools on Windows without dual booting or running a heavy virtual machine. And WSL was the answer. It worked by faking Linux rather than running it. And this was clever, but Linux and Windows don't line up so cleanly. So anything using a Linux file system behavior and unusual syscalls ran slowly or broke. WSL2 took the honest path. Microsoft takes the genuine upstream Linux kernel from kernel.org, compiles it in house, then ships it to you through Windows Update. And that real kernel runs inside an extremely lightweight Hyper-V utility VM that will boot in about a second. And it's wired so tightly into Windows that it will share the file system and networking and can even run Linux graphical apps because it is the actual kernel and not a translation of one. So essentially every Linux program can run unmodified with the same full system call compatibility and far faster file performance than WSL1 had. The lesson is that supporting a platform is often cheaper when you stop imitating it and just run the genuine thing. Docker desktop does this too, running real Linux containers on Windows on top of that same WSL2 kernel. And for 30 years, Windows and Linux were just straight up rivals. But Microsoft ended that fight by doing the last thing people expect, which is compiling Linux itself and mailing it to every Windows machine as a routine update. So they can now boot side by side on the same laptop. And the lesson is that supporting a platform is often cheaper when you stop imitating it and just run the genuine thing.