Original reporting by ZDNet (zdnet.com). This article is based on public statements from Microsoft executives and developers cited in that reporting.
Linux Overtakes Windows Server on Azure
In a request for Microsoft to be added to a Linux kernel security mailing list, Sasha Levin, a Microsoft Linux kernel developer, made a significant admission: Linux usage on Microsoft’s Azure cloud has surpassed that of Windows Server. While the statement was made in a relatively low-profile technical context, its implications are substantial for the DevOps and cloud engineering communities.
The milestone was not sudden. A clear trendline had been visible for years through statements from Microsoft’s own leadership.
The Trendline: Linux on Azure Over the Years
The shift toward Linux on Azure played out gradually and publicly:
- ~2015–2016: Mark Russinovich, Azure CTO, stated that roughly one in four Azure instances were running Linux.
- 2017: Microsoft reported that approximately 40% of Azure virtual machines were Linux-based.
- Fall 2018: Scott Guthrie, Microsoft’s Executive VP of Cloud and Enterprise, said in an interview that “about half” of Azure VMs were running Linux, and added: “Every month, Linux goes up.”
- 2019: Sasha Levin’s disclosure confirmed that Linux had crossed the 50% threshold and now represented the majority of Azure workloads.
Why This Matters for DevOps Engineers
Linux’s dominance on Azure is not simply a customer preference story—it reflects deeper architectural choices Microsoft itself has made. According to Guthrie, native Azure services frequently run on Linux. As a concrete example, Azure’s Software Defined Network (SDN) infrastructure is Linux-based. Microsoft is not just accommodating Linux workloads; it is building its own cloud infrastructure on top of Linux.
This has real consequences for how DevOps teams should approach Azure:
- Container workloads on Azure Kubernetes Service (AKS) default to Linux nodes.
- Azure Functions and App Service both offer Linux hosting plans alongside Windows.
- Azure DevOps and GitHub Actions pipelines commonly target Linux build agents for cross-platform compatibility.
- Infrastructure-as-Code tooling (Terraform, Ansible, Bicep) is typically developed and tested primarily against Linux targets.
Linux’s Broader Enterprise Dominance
The Azure numbers reflect a wider industry reality. Linux has been the dominant server operating system in enterprise environments for years, both on-premises and in the cloud. Windows Server’s market share in server and cloud deployments has declined steadily over the same period.
The momentum behind Linux in enterprise computing is structural rather than incidental. Linux benefits from:
- Lower licensing costs and flexible open-source licensing
- Strong ecosystem support for containers (Docker, containerd, runc are all Linux-native)
- First-class support from cloud providers at the infrastructure level
- Broad toolchain availability for DevOps, observability, and security
- Alignment with open-source software development practices that most engineering teams now rely on
Microsoft’s Open-Source Transformation
The shift at Microsoft has been cultural as well as technical. Guthrie traced Microsoft’s open-source pivot back more than a decade, pointing to the open-sourcing of ASP.NET as an early inflection point. “We recognized open source is something that every developer can benefit from,” he said. “It’s not nice, it’s essential. It’s not just code, it’s community.”
The company subsequently acquired GitHub, contributed heavily to the Linux kernel, and released core developer tooling—including Visual Studio Code and the .NET runtime—as open source. Microsoft has maintained a Platinum-level membership in the Linux Foundation and is one of the top corporate contributors to the Linux kernel by commit volume.
Even former CEO Steve Ballmer, who famously called Linux “a cancer” in 2001, has publicly reversed his position and stated that he now loves Linux.
Linux Distros on Azure and Azure Sphere
At the time of writing (mid-2019), at least eight Linux distributions were available as first-class options on Azure, including Ubuntu, Red Hat Enterprise Linux, CentOS, Debian, SUSE, and others. Microsoft also supports bring-your-own-image scenarios for additional distributions.
Additionally, Microsoft’s Azure Sphere—a hardware and software security platform for IoT and edge devices—runs a custom Linux kernel, as confirmed by Microsoft President Brad Smith. This illustrates that Microsoft’s Linux adoption extends beyond traditional server workloads into embedded and edge computing.
Key Takeaways
- Linux officially surpassed Windows Server as the most-used OS on Microsoft Azure as of 2019, confirmed by a Microsoft Linux kernel developer.
- The shift had been clearly trending in this direction for at least four years prior.
- Microsoft’s own internal services and infrastructure—not just customer workloads—run on Linux.
- This is consistent with Linux’s broader dominance in enterprise server and cloud computing.
- DevOps teams working on Azure should treat Linux as the default target environment unless there is a specific requirement for Windows Server.