TL;DR
- Public Preview: Microsoft has opened Azure Linux 4.0 testing for Azure VMs, scale sets, and container images as a customer-selectable cloud option.
- Cloud Scope: The Fedora-derived, RPM-based OS is tuned for Azure workloads while AKS and WSL support are planned to follow.
- Operational Stake: Databricks’ large migration gives Microsoft a scale test, but support, validation, and FIPS work remain unfinished before general availability.
Microsoft brought the 4.0 Linux release into public testing for virtual machines on June 2, expanding the in-house distribution into a customer-selectable cloud image.
That is a broader role than Azure Linux had in earlier releases. The distribution was already used underneath Microsoft-managed services, including Azure Kubernetes Service, or AKS, where it helped run container hosts. With version 4.0, Microsoft is putting Azure Linux in front of customers as an operating-system image they can choose directly for Azure Virtual Machines.
Version 4.0 is available for Azure Virtual Machines, VM Scale Sets, and container images. Azure Kubernetes Service and Windows Subsystem for Linux support are planned to follow.
Public preview still means test release, not general availability. Microsoft says the evaluation-only Azure Linux preview should not be treated as production-ready while the company finishes support, validation, and compliance work.
What Azure Customers Can Test
Azure Marketplace availability gives administrators a direct path to deploy the image on Azure Virtual Machines and VM Scale Sets, which are groups of virtual machines managed together. Container images are part of the preview as well, so platform teams can test one Microsoft-maintained base across server and container deployments before AKS and WSL images arrive.
Deployment teams can compare VM fleets, scale-set automation, and container pipelines against the same Microsoft-curated package baseline before deciding whether the image fits future production standards.
Microsoft builds the distribution as a Fedora-derived and RPM-based Azure cloud and server OS. It uses the RPM package format and related tooling while Microsoft curates package selection for Azure.
Microsoft also validated the images across Azure VM SKUs and tuned them for Azure compute, storage, and networking rather than consumer desktop Linux. A marketplace image has to behave predictably across different VM sizes, storage paths, and network configurations before customers can treat it as a standard base.
Preview testing covers both package compatibility and Azure-specific operations, including how the image behaves under common compute, storage, and networking combinations.
Version 4.0 includes Kernel 6.18 LTS, dnf5, glibc 2.42, OpenSSL 3.5, systemd 258, Python 3.14, RPM 6.0, and FIPS 140-3 cryptography validation work that remains in progress for general availability.
Databricks moved more than 100,000 VMs and more than one million CPU cores to the OS with no customer-facing incidents, giving the platform a concrete scale test before production availability. Microsoft also cited 27 percent faster image pull times and about 5 percent faster query execution across the Databricks serverless compute fleet.
Fedora lineage does not make the product a drop-in Fedora environment. Administrators should not treat the release as automatically Fedora-compatible because Microsoft keeps a minimal package footprint, curates the package set, and applies Azure-specific hardening.
Where It Fits in Microsoft’s Linux Lineup
Earlier AKS adoption began with Azure Linux’s 2023 Kubernetes availability, and it continued when Azure Linux 3.0 for AKS followed in 2024, before the current VM shift.
Version 4.0 changes the emphasis by making the distribution a VM-focused Linux option for Azure customers, while Azure Container Linux remains the immutable container-host path. For VM users, the split gives Microsoft one conventional server-style image and another locked-down host for container workloads.
Mariner Linux supplies the older lineage. In 2022, the Xbox storefront migration to Mariner used the distribution as the host OS across Xbox Cloud Gaming, PC, console, and mobile, and CBL-Mariner later became Azure Linux.
Version 4.0 keeps that in-house line moving upstream against Fedora while adding supply-chain security work around the distribution. On Azure, the distribution also complements existing endorsed distributions rather than replacing Red Hat Enterprise Linux, Ubuntu Pro for Azure, SUSE Linux Enterprise Server, or other partner offerings.
What Comes Before General Availability
Teams evaluating the preview still face a support boundary. Azure Linux 4.0 can be installed on bare metal or outside Azure, but Microsoft support is focused on cloud-based scenarios, keeping the practical testing path centered on Azure workloads.
Microsoft also plans WSL images for Azure Linux 4.0 and does not plan a graphical desktop environment. Before general availability, support validation and FIPS 140-3 work still have to finish before the OS can move from evaluation status to general availability.
