Microsoft announced Azure Linux 4.0 in public preview at Build 2026. It is Microsoft’s own Linux distribution, built specifically for Azure cloud workloads. This release brings a new kernel, a new package manager, and a companion product called Azure Container Linux.
This guide breaks down what Azure Linux 4.0 actually is, what changed from earlier versions, and whether it matters for your workloads.
What Is Azure Linux 4.0
Azure Linux is a Fedora-derived, RPM-based Linux distribution that Microsoft builds and maintains. It ships only the packages cloud and server workloads need. Microsoft excludes desktop environments, graphical tools, and audio stacks from the base image.
Azure Linux 4.0 uses Fedora 43 as its upstream base. It inherits the same RPM package format and ecosystem as Fedora and Red Hat Enterprise Linux. Microsoft curates the package set, patches security issues, and tunes the OS for Azure compute, storage, and networking.
The distribution runs on Azure Virtual Machines, VM Scale Sets, and container images today. Azure Kubernetes Service (AKS) support and a Windows Subsystem for Linux (WSL) distribution arrive after the initial preview.
How Azure Linux Started
Azure Linux is a Fedora-derived, RPM-based Linux distribution that Microsoft builds and maintains. It ships only the packages cloud and server workloads need. Microsoft excludes desktop environments, graphical tools, and audio stacks from the base image.
Azure Linux 4.0 uses Fedora 43 as its upstream base. It inherits the same RPM package format and ecosystem as Fedora and Red Hat Enterprise Linux. Microsoft curates the package set, patches security issues, and tunes the OS for Azure compute, storage, and networking.
The distribution runs on Azure Virtual Machines, VM Scale Sets, and container images today. Azure Kubernetes Service (AKS) support and a Windows Subsystem for Linux (WSL) distribution arrive after the initial preview.
Microsoft officially announced Azure Linux 4.0 at the Open Source Summit North America on May 18, 2026, and launched the public preview at Build 2026 on June 2.
What Changed in Azure Linux 4.0
| Component | Version | What Changed |
|---|---|---|
| Kernel | 6.18 LTS | Azure-tuned with new hardware drivers, improved Hyper-V integration, GPU and AI accelerator support |
| Package Manager | dnf5 | Rewritten from Python to C++, faster dependency resolution, lower memory usage |
| glibc | 2.42 | Performance improvements in string operations, memory allocation, thread handling |
| OpenSSL | 3.5 | Post-quantum cryptography support, improved QUIC support |
| systemd | 258 | Faster boot sequences, improved service management |
| Python | 3.14 | New JIT compiler, new syntax features |
| RPM | 6.0 | Modernized database backend, improved signature verification |
| FIPS 140-3 | In progress | Expected at general availability |
The package manager switch matters most for day-to-day operations. Earlier versions used tdnf, a stripped-down tool Microsoft built in-house. Version 4.0 switches to dnf5, the same package manager Fedora and Red Hat use. This makes Azure Linux behave more predictably for anyone already familiar with the Red Hat ecosystem.
OpenSSL 3.5 adds post-quantum cryptography support, covering the CRYSTALS-Kyber and CRYSTALS-Dilithium algorithms that NIST standardized. This matters for enterprise customers with forward-looking regulatory requirements.
FIPS 140-3 certification remains in progress and will not arrive until general availability. Government, financial services, and healthcare workloads that require FIPS compliance cannot treat Azure Linux 4.0 as a drop-in replacement for certified RHEL builds yet.
Azure Linux on Virtual Machines
You can deploy Azure Linux 4.0 directly from the Azure Marketplace on any Azure VM or VM Scale Set. Microsoft validates the images across Azure VM SKUs and tunes them for faster startup and provisioning with a reduced package footprint.
Azure Linux works for web applications, databases, and GPU-accelerated AI and ML workloads. It carries no additional OS licensing cost. You pay only for the underlying Azure compute resources.
Azure Linux vs Azure Container Linux
Build 2026 also introduced Azure Container Linux (ACL), an immutable, container-optimized variant for environments with stricter security and compliance requirements. Azure Linux has served as the container host for AKS since 2023, and ACL builds on that foundation as a standalone product.
| Azure Linux (General Purpose) | Azure Container Linux | |
|---|---|---|
| Update model | Package-based (dnf5) | Image-based, immutable, auto-updating |
| Customization | Full package management | Locked-down, minimal surface |
| Best for | General AKS workloads | Regulated, high-security environments |
| SELinux | Supported | Enforcing by default |
| Can you modify it | Yes, install packages freely | No, read-only OS image |
| Availability | Public preview | Generally available |
Azure Container Linux ships as a read-only image. You cannot install packages or change settings on a running system. When an update arrives, the platform swaps the entire image for a new one, with automatic rollback if something breaks. Both products share the same kernel and security update cadence, and Microsoft supports both end to end.
How Azure Linux 4.0 Differs From Ubuntu, Fedora, and RHEL
Azure Linux 4.0 is not a general-purpose distribution you install on a laptop and use as a daily driver. It has no graphical interface, no audio stack, and no desktop environment. The base image does not even include a pager like less. It installs only what cloud and server workloads need.
Setup drops you directly into a console with Bash as the default shell. Creating a user account is optional during setup and easy to miss, which can leave you unable to log in. If you want to test it yourself, download the ISO from the Azure Linux GitHub repository, create a VirtualBox or Hyper-V virtual machine, and boot from the ISO. Do not expect a Fedora-style graphical installer.
| Azure Linux 4.0 | Ubuntu / Fedora / RHEL | |
|---|---|---|
| Built for | Azure cloud workloads only | General use, any environment |
| Desktop or GUI | No | Yes |
| Runs outside its platform | No official support | Anywhere: cloud, bare metal, local |
| Base image size | ~300 MB | 500-600 MB+ |
| Cost | Free, no OS license | Free to paid (RHEL requires subscription) |
| Maintained by | Microsoft | Canonical / Red Hat / community |
| Security defaults | Hardened, minimal attack surface | Standard, varies by distro |
| Package updates | Microsoft-controlled, fast CVE response | Upstream community or vendor |
Ubuntu Server, Fedora Server, and RHEL also strip down their packages compared to desktop variants, but they still carry more than Azure Linux includes by default. Those distributions also run anywhere, including on-premises and on other clouds. Azure Linux 4.0 is explicitly a cloud-only distribution. You can technically run it outside Azure, but Microsoft does not support that configuration.
Why Microsoft Built Its Own Linux Distribution
Linux now runs more instances on Azure than Windows Server does. Most of that Linux traffic runs on distributions Microsoft does not control: Ubuntu, RHEL, SUSE, and Debian. Every time a customer runs Red Hat on Azure, Red Hat collects the support subscription revenue while Microsoft only provides the infrastructure.
If customers standardize on Azure Linux, Microsoft controls the entire stack and supply chain end to end. Microsoft cryptographically signs every package and publishes Software Bill of Materials (SBOM) documents for every release. For regulated industries, holding a single vendor accountable for the entire OS layer is a real selling point.
Amazon built Amazon Linux for the same reason, and Google built Container-Optimized OS. Azure Linux puts Microsoft on a list every major cloud provider already occupies.
Microsoft also positions Azure Linux as the distribution developers can run in WSL during development and then deploy to Azure in production. This removes the environment mismatch problem where code that works locally breaks in the cloud. The pitch gets stronger once WSL Containers ships, letting developers build and test Linux containers locally through WSL before deploying to Azure Linux in production, without leaving Windows.
Should You Care About Azure Linux 4.0
Most individual users and developers do not need to act on this release yet. Azure Linux 4.0 is in public preview and carries a strict not-for-production warning. It targets cloud server and container workloads on Azure specifically. If you run Ubuntu on your PC, deploy apps on RHEL, or use Fedora as your daily driver, nothing here displaces that setup.
What this release does show is that Microsoft now actively maintains a production-grade distribution that already runs LinkedIn and Databricks workloads at scale, and it offers that distribution as a first-class option to any Azure customer.
Pricing
Azure Linux 4.0 costs nothing in software plan charges. You pay only for the Azure infrastructure, meaning the virtual machines on which you run the OS. Your actual price depends on your enterprise agreements and any discounts you hold, and costs vary by deployment region. The plan supports two deployment options: x86_64 (Gen2) and ARM64.
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Azure Linux 4.0 swaps its package manager for the Fedora-standard dnf5, moves to kernel 6.18 LTS, and adds post-quantum cryptography through OpenSSL 3.5. It remains a cloud-only, server-focused distribution with no desktop ambitions. Teams already running mixed Linux distributions across Azure VMs, AKS nodes, and container images now have the option to standardize on one Microsoft-maintained baseline, at no additional OS cost.
