Microsoft shipped Azure Linux 4.0 to public preview at Build 2026, allowing it to run on any Azure virtual machine rather than only as the AKS host OS. The distro, which evolved from the internal CBL‑Mariner project, now targets general‑purpose workloads, turning a formerly appliance‑only Linux into a cloud‑ready option. It supports GPU and AI accelerators.

Azure Linux 4.0 tracks a Fedora 43 snapshot, replacing hand‑crafted spec files with declarative overlays that document every deviation from upstream. It ships kernel 6.18 LTS tuned for Azure, dnf5 package manager, glibc 2.42, systemd 258, OpenSSL 3.5 with post‑quantum support, and RPM 6.0. FIPS 140‑3 certification is in progress and SELinux hardening is enabled by default. rpm signatures are verified aggressively.

The preview makes Azure Linux available through the Marketplace with no extra licensing cost, and Microsoft publishes SBOMs and signed repositories for supply‑chain transparency. Enterprises such as Databricks and LinkedIn have already migrated hundreds of thousands of cores to the distro, and it now powers Azure SQL and Cosmos DB. Azure Linux 4.0 expands its open footprint while giving developers a optimized Linux option. Developers can install it locally via WSL.