Microsoft called Linux a cancer, now ships its own free distro that’s nothing like Ubuntu or Fedora

Azure Linux 4.0 is Microsoft’s own Linux distribution, built for cloud servers and containers on Azure.

Twenty-five years ago, Microsoft’s CEO, Steve Ballmer, called “Linux a cancer that attaches itself in an intellectual property sense to everything it touches.” At Build 2026 in June, the same company shipped its own Linux distribution to the public. Well, at least the product is not a joke!

Azure Linux 4.0 is a real, open-source Linux distribution maintained entirely by Microsoft. It is derived from Fedora, runs on Azure virtual machines, and has already been powering Microsoft’s own infrastructure for years without most people knowing its existence.

What Build 2026 changed is that it is now a free product for anyone to download and use. However, it’s completely different from the other popular Linux Distros like Ubuntu or Mint.

What is a Linux distribution, and where Azure Linux 4.0 fits

Linux itself is just the kernel, the core layer that manages hardware, memory, and processes.

A distribution, or distro, takes that kernel and packages it with everything else an operating system needs, including a package manager to install software, system tools, default configurations, a support structure, and a graphical user interface that helps regular folk use the OS.

Ubuntu, Fedora, Debian, Red Hat Enterprise Linux, and Arch Linux are all distributions built on the same Linux kernel, each with different goals and audiences.

Azure Linux 4.0 is Microsoft’s entry into this list. It is built from Fedora 43 as its upstream base, meaning it uses the same RPM package format, package lineage, and ecosystem as Fedora and Red Hat. The difference is that Microsoft curates the package set, maintains the security patches, and tunes it specifically for running cloud workloads on Azure.