What Canonical announced
Ubuntu Core is the immutable, snap-based variant of Ubuntu. It has mostly lived on embedded and IoT hardware. The cloud images take that model to virtual machines. The images are on the AWS, Azure and Google Cloud marketplaces. Canonical calls them the fastest way to launch Ubuntu Core 26 and explore its operating model on each cloud.
Canonical's own wording on status matters here. Ubuntu Core itself is described as stable, but the public-cloud work required specialized engineering. So Canonical is launching it as a public preview to get feedback from people testing it. Treat the marketplace listings as a test bed, not a production commitment.
How the operating model differs from a normal cloud VM
Canonical's pitch starts from a familiar annoyance. VMs built from one common image drift apart over time as packages, configuration and operational tweaks pile up. Ubuntu Core's answer is to define the system as a set of controlled components, confine them, and deliver updates as complete, auditable revisions.
The features Canonical lists for the cloud images are:
- Immutable foundation: this reduces unintended changes and configuration drift.
- Transactional updates and rollback: a failed update rolls back instead of leaving a half-upgraded system.
- Automatic security updates: the kernel, base system and applications are separate snaps, each updated independently.
- Strict isolation: every component is a snap, and containerization limits the system resources each one can reach.
- Declarative definition: a signed model assertion records the essential components of the system.
These are Canonical's design claims. The announcement doesn't include independent measurements of security or reliability.
What had to change for the cloud
Two engineering changes stand out, and they are the real news here.
Cloud-specific kernel snaps. Everything in Ubuntu Core must be a snap. Canonical's optimized cloud kernels have traditionally shipped as DEB packages. The company has now built cloud-specific kernel snaps to deliver those optimized kernels to the Core images.
Guest agents as snaps. Each cloud's guest agent was traditionally designed around assumptions such as unrestricted filesystem access, arbitrary process execution and the ability to modify the OS. Ubuntu Core challenges those assumptions. Canonical has packaged the required agents as snaps with their own update lifecycle and security policy. Under strict confinement, each agent has to declare the resources and interfaces it needs.
That second change is probably where preview rough edges will show up. Cloud agents handle provisioning and platform integration, and they were written for a world with fewer limits. Canonical itself asks testers to report defects and missing cloud-agent functionality. That is a hint about where to focus your testing.
Who it's for, and who should stay put
Canonical positions Core for virtual appliances, managed services and specialized workloads. Its reasoning is that in a cloud appliance, the person who designed the appliance is often better placed to keep it secure and updated than whoever runs the instance.
It is explicit that this isn't a swap for the usual server. Canonical emphasizes that Ubuntu Core is not a replacement for Ubuntu Server. Server remains the right choice for conventional, general-purpose environments. Those need DEB packages, extensive interactive administration and unrestricted host customization.
In practice:
| Need | Better fit (per Canonical's framing) |
|---|---|
| Fixed-function appliance or managed service | Ubuntu Core |
| Repeatable, auditable update revisions | Ubuntu Core |
| Traditional package management and hands-on admin | Ubuntu Server |
| Heavy host-level customization | Ubuntu Server |
Trying it on Azure
Canonical publishes a launch guide for a pre-built Core image on each cloud, Azure included. The announcement doesn't spell out portal steps, so I won't invent any. A reasonable testing path from the announcement looks like this:
- Follow Canonical's Azure guide to launch the marketplace image.
- Install a snap on the running instance. Canonical points to its Core-on-clouds documentation for this and to snapcraft.io for existing server snaps.
- Read the known limitations of the preview images in Canonical's public-cloud documentation before you build any real expectations.
- File defects and missing cloud-agent functionality on Canonical's public GitHub issue tracker for Ubuntu Core on public cloud. The Ubuntu Core Discourse forum is the place to share what you're building.
For teams that eventually want their own images, Canonical documents building custom Ubuntu Core images for public clouds. It also says it can work with companies, such as ISVs, that want to publish appliance images through a dedicated snap store. One example is an ISV that wants to include Canonical's Expanded Security Maintenance or FIPS components.
Release context
The announcement doesn't cover Azure regions, VM sizes, pricing or feature parity, so don't assume any of those. Check the preview documentation for each.
Ubuntu Core 26 itself isn't new. Canonical's documentation lists it as released on May 14, 2026, built on Ubuntu 26.04 LTS. It describes up to 15 years of security maintenance. Release-wide improvements include a Chisel-based build system, with a 7% smaller base image, and base snap updates dropping from 16 MB to 1.5 MB. Livepatch support is also listed. Those figures describe Core 26 in general. They are not measurements of the cloud images, and they aren't Azure-specific.
Bottom line
For Azure administrators, this is a chance to evaluate an immutable, snap-based Linux for appliance-style workloads. The kernel and guest agent packaging work is the interesting part. It is also the part most likely to have gaps in a preview. Test it in a sandbox subscription, report what breaks, and keep production workloads on a fully supported image until Canonical moves past preview.