Linux on Azure: Microsoft’s New Open-Source Approach to Image Validation

In recent years, Linux has quietly become the dominant operating system on Microsoft Azure, prompting the company to formalise and share the very tooling it uses to validate and publish Linux images. At its core is LISA (Linux Integration Services Automation), an internal framework that Microsoft has now open-sourced under the MIT licence. The newly christened Linux Distribution Service offers a fully automated pipeline—integrating established test suites such as the Linux Test Project (LTP) and kselftest—for guest OS image validation across networking, storage, GPU, HPC and even Confidential VM scenarios (opensource.microsoft.com).

Azure’s Linux momentum

Numerous statements from Azure leadership confirm that more than 60 per cent of both Marketplace offerings and virtual-machine cores on Azure now run Linux (opensource.microsoft.com, LinkedIn). While it may seem surprising given Microsoft’s Windows heritage, this shift reflects the preferences of cloud-native workloads, containerised applications and high-performance computing clusters that benefit from Linux’s modularity and open-source ecosystem.

Behind the scenes, Microsoft maintains its own minimal, container-optimised distro—originally CBL-Mariner, now rebranded Azure Linux—which serves as the base for first-party services and as the graphical component for WSL 2 (Wikipedia).

Introducing the Linux Distribution Service

Rather than keep LISA confined to internal use, Microsoft has chosen to expose it as a public service on Azure. In doing so, they invite both established distributors and independent kernel or security-focused projects to:

Validate their images against comprehensive test suites (LTP, kselftest, syscall tests).
Optimise for performance across networking, storage and specialised hardware (GPUs, FPGAs, HPC).
Publish ready-to-run, security-hardened images directly into the Azure Marketplace. (Windows Forum)

The project repo now includes two main components:

Test orchestrator – coordinates end-to-end test runs in isolated Azure VMs.
Image packer – produces RPM-based images or complete VHDs, signed and versioned for deployment. (Windows Forum)

By open-sourcing LISA under the MIT licence, Microsoft hopes to foster community contributions, transparency and shared ownership of the validation pipeline Windows Forum.

Broader ecosystem context

Azure already supports a broad range of Linux distros—Red Hat Enterprise Linux, SUSE, Canonical’s Ubuntu Pro, Oracle Linux, Flatcar and, as of late, AlmaLinux as an endorsed distribution in the Marketplace (TECHCOMMUNITY.MICROSOFT.COM, Microsoft Azure). Many of these partners rely on Microsoft’s own distro for container-host infrastructure (Azure Linux), while also publishing their customised kernels and packages via the Marketplace.

It may also be helpful to recall that Microsoft’s Linux resources page offers developers extensive tooling, documentation and training for all major distributions on Azure (Microsoft Learn).

Technical deep dive: what LISA brings

Although LISA shares some goals with other image-testing frameworks (e.g. Open QA), its tight integration with Azure yields several advantages:

Scale: automatic provisioning of hundreds of VM instances across multiple regions.
Coverage: pre-built support for networking (multiqueue, SR-IOV), storage (iSCSI, NVMe), INF, GPU passthrough and Confidential VMs.
Traceability: every test run generates a detailed telemetry archive (logs, performance counters, test results) stored in Azure Storage.

Under the hood, LISA pipelines are defined in YAML, enabling partners to fork the repo and customise stages—such as adding bespoke security scanners or compliance checks—while retaining the upstream validation logic.

What this means for Azure users

For organisations deploying Linux workloads on Azure, the new service promises:

Consistency: all images validated against the same baseline ensures predictable behaviour.
Security: signed, tamper-evident images reduce the risk of compromised packages.
Speed: self-service publishing directly to the Marketplace cuts manual QA cycles.

It is perhaps still early days, and community feedback will be crucial to refine test coverage and pipeline ergonomics. Nonetheless, by sharing LISA, Microsoft is signalling a willingness to learn from—and contribute to—the broader Linux ecosystem, rather than dictate terms.

Fair enough Microsoft, watch this space!