Microsoft announced on May 18 an upcoming public preview of Azure Linux 4.0 for Azure Virtual Machines, setting out plans to expand its Linux offering to general-purpose server workloads.
At Open Source Summit North America 2026, the company also announced the general availability of Azure Container Linux, an immutable operating system for container hosting. Microsoft said a broader rollout was planned for Microsoft Build on June 2.
Separate operating systems for VMs and containers
Microsoft describes Azure Linux 4.0 as a Fedora-derived, RPM-based distribution that it builds and maintains. The company says the software is open source, free to use and optimized for Azure infrastructure.
Lachlan Evenson, a principal program manager on Microsoft’s Azure open-source team, described Azure Linux 4.0 as a general-purpose VM offering for Azure customers. He said third-party access to Azure Linux 3.0 had previously been through Azure Kubernetes Service (AKS), and that Microsoft curates Fedora packages and supply-chain components for its cloud platform.
Microsoft says Azure Container Linux is based on Flatcar and designed as an immutable container host. Evenson said its system components are built into the operating-system image, with no package manager for administrators to modify the host. Customer applications run in containers.
Security and update plans
Microsoft says both operating systems have reduced package footprints and a transparent supply chain. The company presents those features as ways to limit the attack surface for cloud-native and AI workloads, including regulated or security-sensitive deployments.
Microsoft’s update plans for Azure Linux called for monthly security patches. Evenson said the company would provide patched images for serious vulnerabilities as soon as fixes became available. He also described optional automatic security upgrades for VMs and AKS, with an option to opt out.
The May 18 announcement did not give a general-availability date for Azure Linux 4.0 or detail production-support terms and migration procedures for the VM offering.
Local development and distribution partners
Evenson said Microsoft planned images for Windows Subsystem for Linux so developers could run Azure Linux locally on Windows. He described the goal as a consistent environment between local development and cloud deployment, and said there were no plans for a graphical desktop environment.
Evenson also said Microsoft would continue working with its existing distribution partners, naming Red Hat and Ubuntu as options Azure customers could still choose.
