Microsoft has made its Azure Linux 4.0 distribution publicly available for free, marking a major expansion of its open-source strategy with a transparent Fedora-based development model for enterprise cloud workloads.
Microsoft has publicly launched Azure Linux 4.0, making its open-source enterprise Linux distribution freely available for anyone to download and use after unveiling it at Build 2026. Previously used internally to power Azure infrastructure, the distribution is now entering public preview as Microsoft’s first broadly available Linux operating system.
The release also marks Azure Linux’s biggest open-source evolution yet. Built on Fedora 43, Azure Linux 4.0 adopts a declarative overlay model that documents every Microsoft modification from upstream Fedora in a public GitHub repository, improving transparency and aligning development with upstream open-source practices.
Designed specifically for Azure cloud infrastructure rather than desktop computing, Azure Linux 4.0 is available for Azure Virtual Machines and VM Scale Sets, with Azure Kubernetes Service (AKS) and Windows Subsystem for Linux (WSL) support planned.
Originally launched as CBL-Mariner in 2019 and renamed Azure Linux in 2024, the distribution already powers production services including Azure Kubernetes Service, Azure SQL and Azure Cosmos DB. Microsoft said LinkedIn has migrated its infrastructure to Azure Linux 3, while Databricks has moved more than 100,000 virtual machines and over one million CPU cores to the platform without customer-facing incidents.
Azure Linux 4.0 replaces Microsoft’s tdnf package manager with dnf5, improving compatibility with the Fedora and Red Hat ecosystem while delivering faster package management. The lightweight distribution also includes Linux Kernel 6.18 LTS, OpenSSL 3.5 with post-quantum cryptography support, cryptographically signed packages and Software Bill of Materials (SBOM) for every release.
