At the North American Open Source Summit in Minneapolis, USA, Microsoft unexpectedly announced its first general-purpose Linux distribution for server scenarios-Azure Linux 4.0. This means that Microsoft, which has been deeply dependent on Linux for a long time, is further acknowledging that it is "in fact a Linux-based" company in the field of cloud and servers in the form of official releases.
The announcement was made by Brendan Burns, co-founder of Kubernetes and current corporate vice president of Microsoft Azure cloud native and management platform and open source business. In his speech, he recalled that when he joined Azure ten years ago, Linux was not the mainstream operating system on the cloud platform, but now Linux has become the main operating system on Azure. He then announced that Microsoft would provide all Azure users with an open source Linux distribution officially supported by Microsoft and freely available on Azure. This sudden news stunned many people in the industry. Even Jim Zemlin, CEO of the Linux Foundation, specifically called him back to the stage to confirm whether he had really "announced a Microsoft Linux distribution."
In fact, Microsoft has used self-developed Linux solutions in specific scenarios many times before, such as Azure Sphere for edge computing devices, and later CBL-Mariner for container platforms. This distribution was later renamed Azure Linux. However, these systems have been mainly serving internal or specific cloud scenarios and are not general-purpose distributions for the public. The launch of Azure Linux 4.0 marks the first time Microsoft has made its own Linux a universal cloud distribution for a wide range of cloud workloads.
According to Lachlan Everson, principal project manager of Microsoft's Azure open source team, the current Azure Linux is divided into two: one line is the new version Azure Linux 4.0, which is positioned as a common virtual machine image for all Azure customers; the other line is Azure Container Linux (ACL) based on Flatcar Container Linux, which is specifically designed to provide a reinforced, secure, and immutable container hosting environment. Previously, Azure Linux 3.0 was only available to third-party customers through Azure Kubernetes Service (AKS) and was mainly used as a container host. In the future, this role will be assumed by Azure Container Linux.
Everson said that Azure Linux 4.0 is an extension of Microsoft's long-term internal operation and iteration of Azure Linux, and it is also a concentrated expression of the evolution of the early Mariner distribution. In terms of technical architecture, Azure Linux 4.0 is based on the upstream Fedora Linux, uses the RPM package of the Fedora ecosystem, and provides source code on GitHub in open source form. On this basis, Microsoft has unified planning and tailoring of software packages and supply chains to make them more suitable for the infrastructure of the Azure cloud platform and achieve deep vertical integration with the underlying Azure environment, thereby providing users with a Linux experience optimized for Azure scenarios.
In terms of delivery form, Azure Linux 4.0 is first provided on Azure as a virtual machine image. Microsoft also plans to bring a desktop-side usage path to developers through Windows Subsystem for Linux (WSL), allowing developers to run Azure Linux locally on Windows 11 devices to obtain a consistent operating environment with the cloud. However, Everson made it clear that Azure Linux will not be built as a desktop Linux distribution in the traditional sense, and there are currently no plans to provide a graphical interface. Its core goal is still to provide a streamlined, reproducible development and operation platform for cloud and server scenarios that is highly consistent with the Azure environment.
Compared with Azure Linux 4.0, Azure Container Linux focuses on containerized workloads, especially the container hosting needs on AKS. Flatcar will still exist as an upstream community project, and Microsoft will strengthen and productize it on this basis to provide a secure, immutable, production-oriented container hosting system by default. Under this immutable architecture, the system does not provide a traditional package manager. System components and applications are "baked" into the system at one time during the image construction phase. It is not recommended to directly modify the system or application packages during operation. Business changes should be delivered and updated through container workloads.
For existing Azure Linux 3.x users, Microsoft promises a smooth upgrade path rather than a disruptive migration. Users can upgrade directly from their existing environment without redeployment, Everson said. In terms of life cycle, the support cycle for a single version of Azure Linux is two years. During this period, Microsoft will select and maintain a relatively stable kernel version and provide a predictable upgrade path and monthly security update rhythm. If a serious vulnerability (such as a major CVE) occurs, Microsoft will roll out the repaired system image as soon as possible instead of just waiting for the routine monthly patching rhythm.
Security is considered one of the core values of Azure Linux. Microsoft hopes to minimize the attack surface exposed by the system by building and self-controlling the entire distribution supply chain, and strengthening the security baseline through selected kernels and streamlined software packages. In terms of operation and maintenance, Azure Linux supports an on-demand "automatic upgrade" mode. Users can choose to automatically complete updates based on security levels. Especially for large-scale deployment scenarios, the system will be gradually upgraded in a rolling manner to reduce the impact on the business. At the same time, users with special loads or who are sensitive to changes can still choose to turn off automatic upgrades and control updates at their own pace.
In terms of broader positioning, Microsoft views Azure Linux as a response to the needs of basic platforms in the "AI native" era. Everson pointed out that currently almost all AI applications are built on the Linux stack. Microsoft has accumulated rich experience in building and operating large-scale Linux platforms for its own AI services (including Microsoft 365, GitHub, and OpenAI's ChatGPT, etc.), and Azure Linux is the product of these experiences, empowering customers to build their own cloud workloads in the AI-native era. According to Microsoft’s public data, more than two-thirds of customer computing cores on Azure now run on Linux. The infrastructure that supports ChatGPT’s processing of billions of requests every day is also based on Linux and Kubernetes.
It is worth noting that Microsoft emphasizes that Azure Linux is not intended to replace the existing Linux distributions in the Azure ecosystem, but as a new option for "full battery configuration". Microsoft said it has been in communication with partners such as Red Hat, who are aware of the launch of Azure Linux. Currently, there are still many officially endorsed Linux distributions on the Azure platform, including Red Hat, Ubuntu, etc. Users can continue to choose their preferred Linux system on Azure as before. Azure Linux assumes the role of an integrated platform that is uniformly provided, uniformly maintained, and security-enhanced by Microsoft, providing options for customers who want a "Microsoft native" cloud experience.
From the previous statement that "Linux is cancer" to today's official release of a Linux distribution for cloud server scenarios and placing it at the core of its strategy, Microsoft's role in the open source and Linux ecosystem has undergone a fundamental change. Beyond the desktop, Microsoft is de facto becoming a company that relies heavily on Linux, and the emergence of Azure Linux 4.0 is undoubtedly a key step in this long-term evolution.
learn more:
https://opensource.microsoft.com/blog/2026/05/18/from-open-source-to-agentic-systems-microsoft-at-open-source-summit-north-america-2026/