At the Open Source Summit North America held in Minneapolis on May 18, Microsoft announced that Azure Linux 4.0 will enter public preview for Azure Virtual Machines on June 17. It will initially be available in the East US and Western Europe regions, with support for Dv5, Ev5, and NVads A10 v5 series instances. A broader rollout is slated for Microsoft Build on June 2. Azure Linux 4.0 marks Microsoft’s first fully rebuilt general-purpose server operating system for Azure VMs based on Fedora Linux; prior versions of Azure Linux (originally launched in 2020 as CBL-Mariner) were designed primarily as container hosts for AKS, Azure Stack HCI, and on-premises cloud infrastructure rather than as standard servers. Version 4.0 introduces a complete RPM package ecosystem while retaining core design principles such as lightweight packaging, transparent supply chains, and enhanced security. Hosted openly on GitHub, it aims to become the default OS platform for cloud-native and AI workloads.
Also unveiled was the General Availability release of Azure Container Linux: this minimalist distribution tailored specifically for Kubernetes worker nodes includes only the kernel, systemd, and container runtime — no SSH daemon or package manager. Its image size is just 1.2 GB (roughly 43% of a similarly sized Ubuntu Server image), enabling boot times under two seconds on standard Azure instances. The newly introduced Blue-Green Node Pools mechanism facilitates zero-downtime OS upgrades and is now integrated into AKS. Additionally, Microsoft announced that its Open Governance Framework for AI Agents (OAGF) entered beta testing on May 22; the production-ready version is set to launch at Microsoft Ignite in November to meet logging and auditing compliance requirements under the EU AI Act, which takes full effect in 2027.