Microsoft has publicly released the first preview of Azure Linux 4.0, a Fedora-based operating system tailored specifically for Azure Virtual Machines and Virtual Machine Scale Sets. The announcement, made in June 2026, marks a significant milestone in Microsoft’s cloud-first Linux strategy, transforming what was once a primarily internal distribution into a free, openly available platform for enterprise customers. Azure Linux 4.0 promises enhanced performance, tighter security, and deeper integration with Azure services, all built on the familiar and widely adopted Fedora ecosystem.
From Internals to Public Preview: The Evolution of Azure Linux
Azure Linux, formerly known as CBL-Mariner, began as a lightweight, internal Microsoft distribution designed for cloud infrastructure and edge computing. For years, it powered Azure’s Kubernetes service, networking appliances, and various microservices. The shift to a public preview with version 4.0 represents a strategic move: offering a first-party Linux distro that customers can run directly on Azure VMs, with the backing of Microsoft’s engineering support and update cadence.
This preview release is based on Fedora, a decision that aligns Azure Linux with one of the leading community-driven Linux distributions known for its cutting-edge features and robust security posture. By adopting Fedora’s package base, Azure Linux gains access to a vast repository of modern software, while Microsoft can focus on performance optimizations, cloud-native integrations, and a streamlined Azure experience.
What’s New in Azure Linux 4.0
Fedora Foundations
At its core, Azure Linux 4.0 is built on Fedora 40 packages and kernel, providing a stable yet up-to-date environment. The use of Fedora means users can expect broad hardware support, recent filesystem improvements, and support for contemporary programming languages and runtimes out of the box. Microsoft has curated a subset of Fedora packages, removing unnecessary components to keep the OS image small—ideal for rapid scaling in cloud environments.
Kernel and Performance Tuning
The Azure Linux 4.0 preview ships with a Microsoft-tuned kernel that includes optimizations for Azure’s hypervisor, faster network stack for accelerated networking, and improved storage performance with NVMe and local SSDs. Early benchmarks shared by the Azure Linux team indicate up to 15% lower latency for common VM-to-VM communications compared to generic Fedora images, thanks to custom kernel parameters and I/O scheduling tailored for Azure infrastructure.
Enhanced Security Features
Security is a cornerstone of Azure Linux 4.0. The distribution integrates Microsoft Defender for Endpoint support directly, along with automatically applied Azure security baselines. It enables Secure Boot, confidential computing extensions, and SELinux policies that are pre-configured for common Azure workloads. The preview also introduces a hardened TCP/IP stack resistant to SYN flood attacks and a read-only root filesystem option for immutable infrastructure patterns.
Native Azure Integration
One of the most compelling aspects of this preview is its tight coupling with Azure services. Azure Linux 4.0 includes the Azure Instance Metadata Service (IMDS) client, managed identity support, and direct integration with Azure Monitor and Azure Policy. Custom scripts and cloud-init modules are optimized for faster boot and configuration, reducing the time from VM creation to workload readiness by an average of 20 seconds compared to other marketplace Linux offerings.
Package Management and Repositories
Microsoft provides its own signed repositories for Azure Linux, built on top of Fedora’s dnf package manager. These repositories include Microsoft-enhanced packages for development toolchains, container runtimes (like CRI-O and containerd), and performance monitoring agents. Users can also pull packages from standard Fedora repositories, offering flexibility for those who need additional software not curated by Microsoft.
Availability and Getting Started
The Azure Linux 4.0 preview is available now for all Azure regions supporting general-purpose and compute-optimized VM series. Users can deploy it from the Azure Marketplace or via CLI with a simple command:
az vm create --resource-group myResourceGroup --name myAzureLinuxVM --image AzureLinux:AzureLinux:4-0:latest
Both x86_64 and ARM64 architectures are supported, catering to the growing demand for ARM-based cloud instances. The preview is free of charge; customers only pay for the underlying compute, storage, and networking resources consumed. Microsoft emphasizes that this is a community preview intended for testing and feedback, not yet recommended for production workloads.
Impact on the Enterprise Linux Market
Azure Linux 4.0 enters a competitive landscape dominated by Red Hat Enterprise Linux, Ubuntu, and SUSE. However, as a first-party Azure offering, it provides unique advantages: unified support from Microsoft, optimized performance, and no additional licensing costs. For enterprises already invested in the Azure ecosystem, it simplifies compliance and support contracts—one vendor for both cloud infrastructure and the operating system.
Analysts note that this move also strengthens Microsoft’s commitment to open source. By basing on Fedora, Microsoft contributes back to the community while offering a differentiated product. It may prompt more organizations to standardize on Azure Linux for their cloud-native and Kubernetes workloads, especially given its close alignment with Azure Kubernetes Service (AKS).
Feedback Channels and Roadmap
Microsoft encourages users to provide feedback through the Azure Linux GitHub repository and a dedicated Azure Feedback forum. The development team has indicated that the final release of Azure Linux 4.0 is slated for later in 2026, with the possibility of long-term support (LTS) branches akin to Fedora’s release cycle. Upcoming features teased include enhanced GPU driver support for AI inferencing, a minimal image for edge devices, and deeper integration with Azure Arc.
A New Chapter for Azure Workloads
With Azure Linux 4.0, Microsoft is offering a second-party Linux that maximizes Azure’s potential. It’s a testament to the company’s evolving philosophy: embracing Linux not just as a workload guest, but as a first-class citizen of the Azure platform. As the preview evolves, it could very well become the default Linux choice for new Azure deployments.